We study animal behaviour, ecology and evolution, focusing mostly on birds as research organisms.

Our fields of interest cover a wide range of topics including social, sexual and parental behaviour and adaptation to environmental changes such as habitat urbanization and climate change.

Our main fields of research:





 Photo credits (from left to right): G. Seress | R.P. Freckleton | N. Fresneau

From our latest research:

— 2024 —

The evolution of sex roles: The importance of ecology and social environment
Fresneau, N., Pipoly, I., Gigler, D., Kosztolányi, A., Székely, T., Liker, A. (2024)  PNAS 121(22). doi: 10.1073/pnas.2321294121

Males and females often have different roles in reproduction, although the origin of these differences has remained controversial. Explaining the enigmatic reversed sex roles where males sacrifice their mating potential and provide full parental care is a particularly long-standing challenge in evolutionary biology. While most studies focused on ecological factors as the drivers of sex roles, recent research highlights the significance of social factors such as the adult sex ratio. To disentangle these propositions, here, we investigate the additive and interactive effects of several ecological and social factors on sex role variation using shorebirds as model organisms that provide the full spectrum of sex role variation including some of the best-known examples of sex-role reversal. Our results consistently show that social factors play a prominent role in driving sex roles. Importantly, we show that reversed sex roles are associated with both male-skewed adult sex ratios and high breeding densities. Furthermore, phylogenetic path analyses provide general support for sex ratios driving sex role variations rather than being a consequence of sex roles. Together, these important results open future research directions by showing that different mating opportunities of males and females play a major role in generating the evolutionary diversity of sex roles, mating system, and parental care.


Complexity of avian evolution revealed by family-level genomes
Josefin Stiller, Shaohong Feng, Al-Aabid Chowdhury, Iker Rivas-González, David A Duchêne, Qi Fang, Yuan Deng, Alexey Kozlov, Alexandros Stamatakis, Santiago Claramunt, Jacqueline MT Nguyen, Simon YW Ho, Brant C Faircloth, Julia Haag, Peter Houde, Joel Cracraft, Metin Balaban, Uyen Mai, Guangji Chen, Rongsheng Gao, Chengran Zhou, Yulong Xie, Zijian Huang, Zhen Cao, Zhi Yan, Huw A Ogilvie, Luay Nakhleh, Bent Lindow, Benoit Morel, Jon Fjeldså, Peter A Hosner, Rute R da Fonseca, Bent Petersen, Joseph A Tobias, Tamás Székely, Jonathan David Kennedy, Andrew Hart Reeve, Andras Liker, Martin Stervander, Agostinho Antunes, Dieter Thomas Tietze, Mads Bertelsen, Fumin Lei, Carsten Rahbek, Gary R Graves, Mikkel H Schierup, Tandy Warnow, Edward L Braun, M Thomas P Gilbert, Erich D Jarvis, Siavash Mirarab, Guojie Zhang (2024) Nature. https://doi.org/10.1038/s41586-024-07323-1

Illustration: Simon Ho & Jon Fjeldså

The study utilized the whole genome sequence data from 363 bird species to reconstruct the most accurate phylogeny of bird families to date. Time-calibration of the phylogenetic tree using fossil records shows that the number of bird species exploded after the mass extinction event that killed dinosaurs 66 million years ago. The average body size of birds decreased during evolutionary changes, although their brain size relative to body mass increased indicating the evolution of their cognitive abilities. This may be related to the evolution of complex social behaviour, avian song and sophisticated tool use in some species. The new phylogenetic tree can serve as a solid backbone for future studies to map the evolutionary history of all extant birds.


Hard life for sons in the nest? Sex-dependent offspring mortality in great tits in urban and forest areas
Ágh, N., Dalvári, H.A., Szabó, K., Pipoly, I., Liker, A. (2024) Avian Research (in press) https://doi.org/10.1016/j.avrs.2024.100169

Sex-biased mortality can occur in birds during development for a variety of intrinsic and extrinsic reasons. The extent of sex-bias in mortality may also be related to environmental conditions. Urban areas often provide poorer conditions for nestling development resulting in higher offspring mortality compared to natural areas, which may accelerate sex differences in offspring mortality in cities. To test this hypothesis, we examined the sex ratio of dead offspring in Great Tits (Parus major) using 427 samples of unhatched eggs and dead nestlings collected between 2013 and 2019 in two urban and two forest areas. The ratio of males in the entire sample of dead offspring was significantly higher than the expected ratio of 1:1, and the strongest sex differences were found in urban areas and in young nestlings. However, the sex ratios of dead fledglings did not differ significantly between study areas and between offspring developmental stages. 29.3% of unhatched eggs contained a visible embryo, but the proportion of unhatched eggs containing an embryo did not differ significantly between sites and habitats.
These results suggest that offspring mortality in Great Tits is influenced by males and highlight the need for large data sets to detect subtle differences between habitats and developmental stages.

— 2023 —

Ember-természet konfliktusok Magyarországon
Ismeretterjesztő előadások és kerekasztal-beszélgetés (2023.11.11, VEAB székház)

Szervező: HUN-REN-PE Evolúciós Ökológiai Kutatócsoport (Pannon Egyetem, Veszprém)
További információ: ITT


Comparison of nestling diet between first and second broods of great tits Parus major in urban and forest habitats
Sinkovics, C., Seress, G., Pipoly, I., Vincze, E., Liker, A. (2023) Animal Biodiversity and Conservation. 46(2): 199–212. https://doi.org/10.32800/abc.2023.46.0199

To understand why early broods tend to be more successful than late broods we investigated the nestling diet and reproductive success of great tit pairs that had both a first and a second brood in the same breeding season. We found that in forest habitats great tit parents delivered similar composition and amount of food per nestlings throughout the breeding season, resulting in similar nestling body mass and survival in both first and second broods. In urban habitats, however, although parents provided similar amounts of food to the second broods they tended to deliver fewer caterpillars. In parallel with this, we observed lower nestling survival in second urban broods than in first broods even though the body mass of surviving nestlings was similar to that of the first broods. These findings suggest that although parents produce smaller second broods in both habitats, they are able to compensate for lower food availability in forest habitats but not in urban habitats, thus leading to reduced food quality and lower offspring survival in urban second broods.


Carotenoid-dependent plumage coloration is associated with reduced male care in passerine birds
Rincón-Rubio, V.A., Székely, T., Liker, A., Gonzalez-Voyer, A. (2023) Behavioral Ecology. 34(5): 872–880. https://doi.org/10.1093/beheco/arad051

Source: https://birdo-azevmadarfotosa.hu/hu/tengelic-mintha-tropusokrol-erkezett-volna

The immense diversity of plumage coloration exhibited by birds is the result of either pigments deposited in the feathers or microstructural arrangements of feather barbules. Some of the most common pigments are carotenoids, which produce bright yellow, orange, and red colors. Here, we hypothesize that carotenoid-dependent plumage coloration functions as a signal of a male’s tendency to invest in offspring care because they play an important role in self-maintenance and may provide key information about individual quality. Using phylogenetic comparative analyses across 349 passerine birds, we show that species that consume carotenoid-rich foods have more carotenoid-dependent plumage coloration than species with carotenoid-poor diets. In addition, carotenoid-dependent plumage coloration is associated with decreased male investment in offspring care. This result suggest that investment in carotenoid-dependent plumage coloration trades off against male investment in offspring care.


Effects of positive frequency-dependent learning, learning mistakes, and immigration on complex cultures–Validation on the song of collared flycatcher (Ficedula albicollis) by individual-based modelling
Barta, K.A., Garamszegi, L.Zs., Scheuring, I., Zsebők, S. (2023) Frontiers in Ecology and Evolution. 2023(11). https://doi.org/10.3389/fevo.2023.1040550

In stable polymorph cultures, cultural diversity and stability are both important aspects as they can ensure individual- and group recognition and variability when in need to adapt to changing environments. With the help of an individual-based model we’ve tried to recreate features of stable polymorph cultures by implying a combination of conflicting mechanisms: positive frequency-dependent social learning, learning mistakes and immigration. As a model cultural system, we used the complex song culture of the collared flycatcher (Ficedula albicollis). We’ve shown that further stabilizing mechanisms are needed if we intend to maintain a higher cultural diversity on the long term. Metastable states, found in the population-level cultural diversity, raise awareness to animal cultures’ possible sensitivity to external factors.


Multiple paternity is related to adult sex ratio and sex determination system in reptiles
Pipoly, I., Mészáros, G., Bókony, V., Vági, B., Székely, T., Liker, A. (2023) Journal of Evolutionary Ecology. 36(6): 935–944. https://doi.org/10.1111/jeb.14185

Recent studies suggest that adult sex ratio (ASR, proportion of males int he adult population) can be a major driver of social mating systems and parental care. ASR may also influence genetic mating systems. For instance male-skewed ASRs are expected to increase the frequency of multiple paternity (defined here as a clutch or litter sired by two or more males) due to higher rates of coercive copulations by males, and/or due to females exploiting the opportunity of copulation with multiple males to increase genetic diversity of their offspring. Here we evaluate this hypothesis in reptiles that often exhibit high frequency of multiple paternity although its ecological and life-history predictors have remained controversial. Using a comprehensive dataset of 81 species representing all four non-avian reptile orders, we show that increased frequency of multiple paternity is predicted by more male-skewed ASR, and this relationship is robust to simultaneous effects of several life-history predictors. Additionally, we show that the frequency of multiple paternity varies with the sex determination system: species with female heterogamety (ZZ/ZW sex chromosomes) exhibit higher levels of multiple paternity than species with male heterogamety (XY/XX) or temperature-dependent sex determination. Our across-species comparative study provides the first evidence that genetic mating system depends on ASR in reptiles


Expansion of the sharp-snouted rock lizard (Dalmatolacerta oxycephala) in the southern part of the island of Cres
Tóth, T., Varga, N., Gál, J., Kocsis, B. (2023) Natura Croatica: Periodicum Musei Historiae Naturalis Croatici. 32(1): 121–126. https://doi.org/10.20302/NC.2023.32.7

In 2005, the sharp-snouted rock lizard (Dalmatolacerta oxycephala) appeared on the island of Cres, possibly through human activity. Previously, only the Dalmatian wall lizard (Podarcis melisellensis) inhabited Osor town. Despite P. melisellensis typically outcompeting D. oxycephala where they coexist, in Osor we showed, that D. oxycephala displaced P. melisellensis within 16 years. The two species were not observed together in the same locations. While D. oxycephala prefers tall stone walls, it was also found on shorter walls along the road to Lošinj. The continued spread of D. oxycephala on Cres may negatively impact the native Dalmatian wall lizard.


Data on the frog trade in the 20th century in Hungary
Tóth T., Gál J., Varga N., Lukács A., Kocsis B. (2023) Biharean Biologist, 17(1), 39-44 [LINK]

This review oversees the frog trade in the 20th century in Hungary. Frog consumption in Hungary was not popular before World War II, therefore captures for this purpose was low too. However, interest in live specimens from foreign research institutes grew in the late 1920s. Significant frog capturing for consumption began in the late 1950s, with exports mainly to France, Switzerland, Italy, and West Germany. In the 1960s, Hungary exported 100-130,000 kg of frogs multiple times a year, equivalent to around 2-2.5 million individuals annually. Some reports suggest that by the early 1970s, this figure reached 1 million kilograms. Edible frogs (Pelophylax kl. esculentus), marsh frogs (Pelophylax ridibundus) and pool frogs (Pelophylax lessonae), which resembled edible frogs, were the primary species affected. Frog capture and export ceased in 1974 when all Hungarian amphibians and reptiles became protected.


— 2022 —


Delay in arrival: lineage-specific influence of haemosporidians on autumn migration of European robins
Ágh, N., Csörgő, T., Szöllősi, E. (2022) Parasitology Research. 121(10): 2831–2840. https://doi.org/10.1007/s00436-022-07621-5

Haemosporidian blood parasites are one of the most studied parasites with reliable impacts on the life-history traits of their bird hosts. However, their roles in bird migration are less studied. In this recent study, we tested the relationships between infection for parasite genera, the three most frequent parasite lineages, body condition (body mass, fat deposit), and the timing of autumn migration in the European Robin. Firstly, we found a delay in the timing of migration in infected juveniles, but no significant differences in the actual condition. However, when we analyse the lineages separately, we found that the prevalence of parasite lineages correlated with the body mass, fat storage, and timing of autumn migration of the birds in a different direction. Our results, therefore, emphasize the importance of testing the impacts of the different parasites individually.


The evolution of parental care in salamanders
Vági B., Marsh D., Katona G., Végvári Zs., Freckleton R.P., Liker A., Székely, T. (2022) Scientific Reports. 12:16655, https://doi.org/10.1038/s41598-022-20903-3

Complex parenting has been proposed to contribute to the evolutionary success of vertebrates. Using 181 species that represent all major lineages of an early vertebrate group, the salamanders and newts, here we show that fertilisation mode is tied to parental care: male-only care occurs in external fertilisers, whereas female-only care exclusively occurs in internal fertilisers. Internal fertilisation opens the way to terrestrial reproduction, because fertilised females are able to deposit their eggs on land, and with maternal care provision, the eggs could potentially develop outside the aquatic environment.


The cost of egg production drives female-biased mortality in avian species
Romano A., Liker A., Bazzi G., Ambrosini R., Møller A.P., Rubolini D. (2022) Evolution. https://doi.org/10.1111/evo.14623

Among avian species, the differential cost entailed by either sex in competition for mates has been regarded as the main evolutionary influence on sex differences in mortality rates. However, empirical evidence suggests that sex-biased adult mortality is mainly related to differential energy investment in gamete production. According to this hypothesis, we showed that greater annual egg productivity resulted in higher mortality rates of females relative to males. Mating system was secondarily important, with species in which males were more involved in mating competition having more equal mortality rates between the sexes.


Does ecology and life history predict parental cooperation in birds? A comparative analysis
Long X., Liu Y., Liker A., Weissing F., Komdeur J., Székely T. (2022) Behavioral Ecology and Sociobiology. 76 (7): 1-12, https://doi.org/10.1007/s00265-022-03195-5

Parental care is a ubiquitous strategy in animals. Besides sharing parenting duties in humans and many bird species, single parenting is also observed in animal taxa, such as in most fishes and mammals. To understand which factors can explain the diversified parental care strategies, we apply the most advanced comparative analyses with the largest datasets on parental care behavior in birds. Here, we show that males and females share care duties more equally when species live in groups or have high-demand offspring who are born helpless. However, parental care patterns are not associated with diet (e.g., plant-eating and animal-eating), nest type (e.g., platform nests and cavity nests) or body size. Our study therefore suggests that living in groups during the breeding season and offspring demand are important for parents to make their care decisions.


Latitudinal gradients in avian colourfulness
Cooney C.R., He Y., Varley Z.K., Nouri L.O., Moody J.A.C., Jardine, M.D., Liker A., Székely T., Thomas, G.H. (2022) Nature Ecology and Evolution. 6: 622-629, https://doi.org/10.1038/s41559-022-01714-1

After generating a dataset on plumage colouration for over 4,500 bird species, the authors show that tropical species are more colourful than temperate species, confirming a long-held but difficult-to-prove belief.




Evolution of social organization: phylogenetic analyses of ecology and sexual selection in weavers
Song Z., Liu Y., Liker A., Székely T. (2022) American Naturalist. 200: 250-263, https://doi.org/10.1086/720270

Crook published a landmark study on the social organization of weavers (or weaverbirds, family Ploceidae) that contributed to the emergence of sociobiology, behavioral ecology, and phylogenetic comparative methods. We revisited Crook’s hypotheses using modern phylogenetic comparative methods on an extended data set of 107 weaver species. We showed that both diet and habitat type are associated with spatial distribution and that the latter predicts mating system, consistent with Crook’s propositions. The best-supported phylogenetic path model also supported Crook’s arguments and uncovered a direct relationship between nonbreeding distribution and mating system.


Sex-roles in birds: phylogenetic analyses of ecology, life histories and social environment
Gonzales-Voyer A., Thomas G.H., Liker A., Krügger O., Komdeur J., Székely T. (2022) Ecology Letters. 25: 647-660, https://doi.org/10.1111/ele.13938

Sex roles describe sex differences in courtship, mate competition, social pair-bonds and parental care. A key challenge is to identify associations among the components and the drivers of sex roles. We found extensive variation and lability in proxies of sex roles, indicating remarkably independent evolution among sex role components, and that the social environment is central to explaining variation in sex roles among birds.


Extreme Hot Weather Has Stronger Impacts on Avian Reproduction in Forests Than in Cities
Pipoly I., Preiszner B., Sándor K., Sinkovics Cs., Seress G., Vincze E., Bókony V., Liker A. Frontiers in Ecology and Evolutionhttps://doi.org/10.3389/fevo.2022.825410

Relationship between the number of hot days during the nestling period, and body mass of great tit (Parus major) nestlings. Symbols represent brood means, from two urban (red) and two forest (blue) populations in Hungary

Climate change and urbanization are among the most salient human induced environmental effects. Heat events have become more frequent in the past decades, and urban areas have generally higher temperatures than surrounding natural areas, due to urban heat island effect. But, it is poorly known whether urban individuals can adapt better to the higher temperatures, or suffer more because they experience heat much more than conspecifics in natural habitats. We investigated whether the extreme heat events have the same or different effect on the development and survival of nestlings in two urban and two non-urban populations, by studying 760 great tit broods from two urban and two forest populations over six years. We found that forest populations are more vulnerable to heat, as nestlings’ body mass decreased with the number of hot days in the forests but not in the cities, and nestling mortality increased more rapidly with the number of hot days in the forests than in the cities. Our paper is one of the first studies looking at the joint effects of climate change driven extreme heat events and habitat urbanisation on warm-blooded animals.

The paper is also covered in Frontiers Media Blog.


Urbanization’s effects on problem solving abilities: a meta-analysis
Vincze, E. & Kovács, B. (2022) Frontiers in Ecology and Evolution. https://doi.org/10.3389/fevo.2022.834436

Spotted hyena (Crocuta crocuta), Great tit (Parus major) and Eastern gray squirrel (Sciurus carolinensis) solving a cognitive task. Photo credits: Lily Johnson-Ulrich (top), Pizza Ka Yee Chow (bottom).

Cognitive abilities are often assumed to be advantageous for animals in urban habitats, but relatively few studies tested this assumption. In our meta-analysis, we compared 12 studies that tested whether urban animals have better problem-solving abilities compared to their less urbanized conspecifics. These studies were published between 2009 and 2021, and were performed mostly on birds, whereas a quarter of them used mammals as study species. We found a statistically non-significant trend that urban animals are more successful and faster problem-solvers compared to their less urbanized conspecifics. However, both solving success and solving latency effect sizes were highly heterogeneous, therefore hard to generalize. We conclude that more studies are needed to either confirm or disprove this trend and explain the high heterogeneity.


Differences in feather structure between urban and forest great tits – constraint or adaptation?
Sándor, K., Seress, G., Sinkovics, Cs., Péter, Á., Liker, A. (2022) Journal of Avian Biology. https://doi.org/10.1111/jav.02922

Despite its potential significance, the plumage structure of urban birds is largely unexplored and it is unclear whether and how it responds to urban ecological processes such as different constraints (e.g. food limitation) and selection pressures (e.g. warmer microclimate). In this study, we compared several structural properties of contour, primary and tail feathers between two forest and two urban great tit (Parus major) populations. Our results show that the urban environment affects only a few structural properties of contour and wing feathers and these differences are present only in the plumage of first-year birds. The differences in the structure of wing feathers between urban and forest first-year birds suggest nutritional constraints experienced by birds during nestling development, while the looser structure of contour feathers in urban first-year birds may promote them a better heat dissipation, indicating adaptive responses to the warmer microclimate in cities.

— 2021 —

Great tits feed their nestlings with more but smaller prey items and fewer caterpillars in cities than in forests
Sinkovics, Cs.Seress, G., Pipoly, I., Vincze, E., Liker, A. (2021). Scientific ReportsDOI: 10.1038/s41598-021-03504-4

We studied the effect of urbanisation on the diet of great tit nestlings, and collected data on the parental provisioning behaviour of urban and forest great tits in 3 years that varied both in caterpillar availability and in reproductive success of the birds. In all years, urban parents provisioned caterpillars in a smaller proportion to their nestlings, but the total amount of food per nestling did not differ between habitats. In the two years with much lower reproductive success in urban than forest habitats, urban parents had higher provisioning rates, but provided more non-arthropod food and brought smaller prey items than forest parents. In the year with reduced habitat difference in reproductive success, urban parents were able to compensate for the scarcity of caterpillars by provisioning other arthropods and by delivering larger caterpillars than in the other years.


Conservation biology research priorities for 2050: a Central and Eastern European perspective
Csákvári, E., Fabók, V., Bartha, S., (…) Liker, A., (…), Báldi, A. (2021). Biological Conservation, DOI: 10.1016/j.biocon.2021.109396

One of the main goals of the EU Biodiversity Strategy for 2030 is to avoid further loss of biodiversity and to restore ecosystems. The study suggests fourteen priority research topics relevant to biological conservation that should be targeted by stakeholders, primarily policy makers and funders to focus research capacity to these topics. The main themes include a wide range of approaches and solutions such as innovative technologies, involvement of local stakeholders and citizen scientists, legislation, and issues related to human health. These indicate that solutions to conservation challenges require a multidisciplinary approach in design and a multi-actor approach in implementation. Although the identified research priorities were listed for Hungary, they are in line with European and global biodiversity strategies, and can be tailored to suit other Central and Eastern European countries as well.


Double-brooding and annual breeding success of Great Tits (Parus major) in urban and forest habitats
Bukor, B., Seress, G., Pipoly, I., Sándor, K., Sinkovics, Cs., Vincze, E. & Liker, A. (2021). Current Zoology, DOI: 10.1093/cz/zoab096

The proportion of double- vs. single-brooded female great tits at the 4 study sites (2013–2019)

Urbanization may facilitate multiple breeding per year in seasonally reproducing species that may potentially compensate urban birds for their lower breeding success per breeding attempt. We studied two urban and two forest populations, and our results, however, did not support this expectation, because we found no consistent difference in the probability of double-brooding by female Great Tits (Parus major) between urban and forest habitat types. Urban females produced fewer offspring annually than forest females.


Sex Role Reversal and High Frequency of Social Polyandry in the Pheasant-Tailed Jacana (Hydrophasianus chirurgus)
Fresneau, N., Lee, Y.-F., Lee, W.-C., Kosztolányi, A., Székely, T., & Liker, A. (2021). Frontiers in Ecology and Evolution, 9, 755, DOI:  10.3389/fevo.2021.742588

A male (above) and female (below) Pheasant-tailed jacana copulating above their nest (Photo by N. Fresneau).

Sex-role reversal is a type of breeding system where males invest more than females in parental care while the females invest in mating competition and producing multiple broods for several mates. This type of mating is not common in birds as it is only present in less than 2% of the species. This study aimed to fill knowledge gaps by investigating the sex role differences in the breeding behaviour of the pheasant-tailed jacana, by observing and monitoring a breeding population.

In our results we showed that the polyandrous females performed mating and laying sequentially with different mates but maintained the pair bonds simultaneously with multiple males. We could estimate that the average number of mates per female was 2.4 and that at least 81.8% of the females in the population were polyandrous. We also found that the females provided most of the territory defence toward conspecific, but males also participated at a lower extent in agonistic behaviours. Contrary to what was expected, we showed that males spent more time than females on courtship behaviour. Finally, our observations corroborated that brood care is predominantly provided by males, nevertheless females were also participating to some degree in brood attendance but never in direct care.


Degree of anisogamy is unrelated to the intensity of sexual selection
Mokos, J., Scheuring, I., Liker, A., Freckleton, R. & Székely, T. (2021). Scientific Reports, 11: 19424, DOI: 10.1038/s41598-021-98616-2

Males and females often display different behaviours and, in the context of reproduction, these behaviours are labelled sex roles. The Darwin–Bateman paradigm argues that the root of these differences is anisogamy (i.e., differences in size and/or function of gametes between the sexes) that leads to biased sexual selection, and sex differences in parental care and body size. The results question the first step of the Darwin–Bateman paradigm, as the extent of anisogamy does not appear to predict the intensity of sexual selection. The only significant predictor of sexual selection is the relative inputs of males and females into the care of offspring.


Contrasting effects of the COVID-19 lockdown on urban birds’ reproductive success in two cities
Seress, G., Sándor, K., Vincze, E., Pipoly, I., Bukor, B., Ágh, N., Liker, A. (2021). Scientific Reports 11, 17649. DOI: 10.1038/s41598-021-96858-8

The lockdown in 2020 greatly affected the levels of human disturbance in urban parks. Artwork: Matt Carlson

Human activity is a fundamental feature of cities affecting local wildlife. Due to the lockdowns – as a response to the COVID-19 pandemic – human mobility and traffic greatly reduced in cities worldwide, resulting in decreased human disturbance in many (but not all) urban parks. To better understand the ecological effects of human activity on urban wildlife we assessed changes in the reproductive success of great tits (Parus major) at urban and forest habitats using long-term datasets. At one of our urban sites, the strongly (-44%) reduced human disturbance in 2020 did not increase birds’ reproductive output relative to the forest habitat where human disturbance was low in all years. At the other urban site, recreational human activity greatly increased (+40%) during the lockdown and this was associated with strongly reduced nestling body size compared to the pre-COVID reference year. These results do not support that urban great tits benefited from reduced human mobility during the lockdown and also highlight that a few months of ‘anthropause’ is not enough to counterweight the detrimental impacts of urbanization on local wildlife populations.


Uncertainty in experts’ judgments exposes the vulnerability of research reporting anecdotes on animals’ cognitive abilities
Sándor, K., Könnyű, B. & Miklósi, Á. (2021). Scientific Reports 11, 16255. DOI: 10.1038/s41598-021-95384-x

https://twitter.com/UNIVERSALERPE/ status/1284493637469044739

Expertise in science, particularly in animal behaviour, may provide people with the capacity to provide better judgments in contrast to lay people. We relied on citizen science and developed a questionnaire to measure whether experts in ethology and ornithology can provide a more objective, accurate evaluation of a recently reported anecdote on Atlantic puffin (Fratercula arctica) “tool use”. We found that no major differences among the evaluators. At the group levels, even the expert respondents were relatively uncertain with regard to the action of the bird seen on the video. Our results strongly emphasise that anecdotes lack the power for being analysed in any deeper way apart from providing a description of the action and the context, thus should not be used to argue about mental processes.


Consistency and plasticity of risk-taking behaviour towards humans at the nest in urban and forest great tits, Parus major
Vincze, E., Bókony, V., Garamszegi, L. Z., Seress, G., Pipoly, I., Sinkovics, Cs., Sándor, K. & Liker, A. (2021). Animal Behaviour 179: 161-172. DOI: 10.1016/j.anbehav.2021.06.032

Drawing: Ernő Vincze

Urban animals often show bolder behaviour towards humans than their nonurban conspecifics. In this study, we monitored the parental risk-taking behaviour of almost 400 great tit pairs over 6 years. We found that urban great tits alarm-call at humans more than their forest conspecifics and urban females stay on the nest upon human disturbance more often than forest birds. Furthermore, staying on the nest is repeatable and increases during incubation but not across years, which suggests that it might be a good proxy of boldness in female birds. We found no difference between cities and forests in the repeatability or plasticity of either risk-taking behaviour.


Evolution of large males is associated with female-skewed adult sex ratios in tetrapods
Liker, A., Bókony, V., Pipoly, I., Lemaitre, J-F., Gaillard, J-M., Székely, T. & Freckleton, R. (2021). Evolution, 75: 1636-1649, DOI: 10.1111/evo.14273

By comparative analyses of data of 400+ reptile, bird and mammal species, we show that sex-biased mortality drives skewed adult sex ratios, which in turn can lead to biased sexual size dimorphism. These findings provide evidence that skewed ASRs in amniote populations can result in the rarer sex evolving large size to capitalize on enhanced mating opportunities.



Social organization in ungulates: revisiting Jarman’s hypotheses
Szemán, K., Liker, A. & Székely, T. (2021). Journal of Evolutionary Biology, 34: 604-613, DOI: 10.1111/jeb.13782

Photo credit: Prof Oliver Krüger

Consistently with Jarman’s (1974) proposition, our phylogenetically controlled anylyses confirmed that species’ ecology predict group size, since grazing ungulates typically live in open habitats and form large herds. Group size, in turn, has a knock-on effect on mating systems and sexual size dimorphism, since ungulates that live in large herds exhibit polygamy and extensive sexual size dimorphism. Phylogenetic confirmatory path analyses suggest that evolutionary changes in habitat type, feeding style and body size directly (or indirectly) induce shifts in social organization.


Urban nestlings have reduced number of feathers in Great Tits (Parus major)
Sándor, K., Liker, A., Sinkovics, Cs., Péter, Á., Seress, G. (2021). IBIS, DOI: 10.1111/ibi.12948

The studied feather tract area on a 7 days old great tit nestling. Photo: Krisztina Sándor

The plumage of birds plays an essential role in thermal insulation and influences the heat tolerance of birds that can be determined both by the number and the density of feathers. In this study, we investigated the effects of the urban environment (that is usually is characterized by higher temperatures and food limitation) on these plumage characteristics on wild birds. To do this, we compared the number of feathers in nestlings between urban and forest Great Tits using a novel non-invasive method. We showed that urban nestlings have fewer feathers than their forest counterparts at 6–9 days old, but their feathers are concentrated in a reduced feather tract area that results in a slightly higher feather density but also larger bare body surfaces. All of these may help urban birds to adapt to higher urban temperatures by facilitating heat dissipation.

The paper has also been covered in a British Ornithologists’ Union blogpost.

Are evolutionary transitions in sexual size dimorphism related to sex determination in reptiles?
Katona, G., Vági, B., Végvári, Zs., Liker, A., Freckleton, R., Bókony, V. & Székely, T. (2021). Journal of Evolutionary Biology, 34:594-603, DOI: 10.1111/jeb.13774

Sex determination systems are highly variable in vertebrates, although neither the causes nor the implications of this diversity are fully understood. Theory suggests that sex determination is expected to relate to sexual size dimorphism, because environmental sex determination promotes sex-specific developmental bias in embryonic growth rates. Using phylogenetically informed analyses, we find that sexual size dimorphism is associated with sex determination: species with TSDIa sex determination (i.e. in which the proportion of female offspring increases with incubation temperature) have more female-biased size dimorphism than species with TSDII (i.e. species in which males are produced at mid temperatures). Our results support the prediction that sexual size dimorphism is linked to sex-dependent developmental variations caused by environmental factors and also by sex chromosomes.



— 2020 —

How to report anecdotal observations? A new approach based on a lesson from “Puffin tool use”
Sándor, K. & Miklósi, Á. (2020). Frontiers in Psychology, 11:555487, DOI: 10.3389/fpsyg.2020.555487

Do puffins really use tools? Photo: www.islandvista.co.uk/our-wildlife

There has been a long history of anecdotal reports in the field of natural history and comparative (evolutionary) animal behavior and nowadays we also see a decreasing trend of reporting anecdotes in scientific journals. As anecdotes can be important drivers for future research, with this opinion article we wanted to draw attention to the fact that these reports should follow some standards and authors should be careful in avoiding over-interpretations. We used a recently published article (which received a lot of media hype) as an example to point out the problems with such anecdotal observations in general, and suggest ways to improve the information exchange among researchers.


Connecting the data landscape of long‐term ecological studies: the SPI‐Birds data hub
Culina, A. (…) Liker, A. (…) Seress, G. (…) Visser, M.E. (2020). Journal of Animal Ecology, DOI: 10.1111/1365-2656.13388

SPI-Birds logo

The paper introduces and describes the „SPI‐Birds Network and Database” (www.spibirds.org) – a large‐scale initiative that connects data from, and researchers working on, studies of wild populations of individually recognizable birds. SPI‐Birds acts as a data hub and a catalogue of studied populations. It prevents data loss, secures easy data finding, use and integration, and thus facilitates collaboration and synthesis.


Parental care forms are predicted by climatic and social environments in Anura.
Vági, B., Végvári, Zs, Liker, A., Freckleton, R.P. & Székely, T. (2020). Global Ecology and Biogeography, DOI: 10.1111/geb.13113

Photo credit: Robert P Freckleton

Amphibians exhibit unusually diverse reproductive modes, including a wide array of parental care strategies. The evolutionary drivers of this diversity, however, remain unclear. Our results showed that climatic effects contribute to parental care diversity: in cool and humid climates the males provide offspring attendance, whereas in predictable temperatures endotrophy occurs, whereby the female provides all nutrients for the offspring until metamorphosis. In addition, we found other associations between mating systems and forms of parental care: uniparental clutch attendance by males is present in species with territorial defence, whereas cooperative nest building co‐occurs with sperm competition. The type of parental care is not associated with adult sex ratios.


Ecology, phylogeny, and the evolution of developmental duration in birds.
Cooney, C. R., Sheard, C., Clark, A. D., Healy, S. D., Laland, K. N., Liker, A., Street, S.E., Troisi, C., Thomas, G.H., Székely, T., Hemmings N. & Wright, A.E. (2020). Nature Communications, 11, Article number: 2383, DOI: 10.1038/s41467-020-16257-x

The duration of the developmental period represents a fundamental axis of life-history variation, yet broad insights regarding the drivers of this diversity are currently lacking. Here, we test mechanistic and ecological explanations for the evolution of developmental duration using embryological data and information on incubation and fledging for 3096 avian species. Developmental phases associated primarily with growth are the longest and most variable, consistent with a role for allometric constraint in determining the duration of development. In addition, developmental durations retain a strong imprint of deep evolutionary history and body size differences among species explain less variation than previously thought. Finally, we reveal ecological correlates of developmental durations, including variables associated with the relative safety of the developmental environment and pressures of breeding phenology. Overall, our results provide broad-scale insight into the relative importance of mechanistic, ecological and evolutionary constraints in shaping the diversification of this key life-history trait.

The paper is covered in international and Hungarian media: The GuardianBehind the PaperNatGeo [in Hungarian], 24.hu [in Hungarian]


Impacts of urbanization on stream fish assemblages: the role of the species pool and the local environment.
Czeglédi I., Kern, B., Tóth, R., Seress, G., Erős, T. (2020). Frontiers in Ecology and Evolution, DOI: 10.3389/fevo.2020.00137

Dominant fish species in the surveyed urban streams

Community structure in urban stream ecosystems is the sum of multiple processes, including local environmental and catchment level effects – disentangling these is a prerequisite for understanding the impacts of urbanization on the biota. We studied the importance of the degree of urbanization, the local stream environment and the regional species pool on the assembly of stream fishes in 29 streams in the Pannon Biogeographic Region, Hungary. We found that the studied streams reacted to the degree of urbanization in a strongly individual manner and that urbanization variables purely explained only a very small proportion of variance in the data. Our results clearly indicate that the downstream species pool was the most important determinant of fish species richness, community composition and abundance at urban stream sites. Overall, the results highlight that the degree of urbanization is not a strong determinant of local stream habitat and fish community characteristics in this region and that dispersal mechanisms from non-urban segments strongly influence community organization.


The effect of artificial light at night on the biomass of caterpillars feeding in urban tree canopies.
Péter, Á.* & Seress, G.*, Sándor, K., Vincze, E., Klucsik, K.P., Liker, A. (2020). Urban Ecosystems, DOI: 10.1007/s11252-020-00999-z
*Áron Péter and Gábor Seress are joint first authors of this study

Night lights in Veszprém Photo: Balázs Czakó (www.czakobalazs.com)

Night lights in Veszprém. Photo: Balázs Czakó (www.czakobalazs.com)

Artificial light at night (ALAN) in cities disrupts the day-night cycle, which can strongly affect urban ecosystems. In our study, we tested whether ALAN affects the biomass of arboreal caterpillar populations, which are a major component of the diet of many animals. We estimated caterpillar biomass from thousands of frass samples collected from 36 focal trees in two cities, over four consecutive years, and measured local light intensity at night at each focal tree. Despite the repeatable variation of caterpillar biomass between trees, we found no negative (or positive) effect of ALAN on caterpillars. It is possible that ALAN’s effect on caterpillars was masked by other local environmental factors; that ALAN has multiple, antagonistic effects acting during different stages of the lepidopteran life cycle; or that even the lower levels of our sites’ public lighting are strong enough to cause serious detrimental effects for caterpillars, resulting in their uniformly low biomass.


Food availability limits avian reproduction in the city: An experimental study on great tits Parus major.
Seress, G., Sándor, K., Evans, K.L., Liker, A. (2020). Journal of Animal Ecology, DOI: 10.1111/1365-2656.13211

Photo credit: G. Seress

Avian reproductive success is often reduced in urban areasand although previous work suggests that this is partly driven by food limitation (i.e., low insect availability during the breeding season), robust experimental evidence is not yet available. Thus, we tested core predictions of the food limitation hypothesis using a controlled experiment that provided supplementary insect food to great tit nestlings in urban and forest habitats. Provisioning rates were similar across habitats and control and supplemented broods, but supplemented (and not control) broods consumed large quantities of supplementary food. As predicted, we found that nestlings in (a) urban control broods had smaller body size and nestling survival than forest control broods; (b) forest supplemented and control broods had similar body size and survival rates; (c) urban supplemented nestlings had larger body size and survival rates than those in urban control broods; and crucially (d) urban supplemented broods had similar body size and survival rates to nestlings in forest control broods.

Our results provide rare experimental support for the strong negative effects of food limitation on urban birds’ breeding success, and also suggest suggest that urban stressors other than food shortage contributed relatively little to the reduced avian breeding success. Finally, given the impacts of the amount of supplementary food that we provided and taking clutch size differences into account, our results suggest that urban insect populations in our study system would need to be increased by a factor of at least 2.5 for urban and forest great tits to have similar reproductive success.

The paper is covered in international and Hungarian media, e.g.: British Ornithologists’ Union, British Ecological SocietyNational Geographic (in Hungarian)

Does offspring sex ratio differ between urban and forest populations of great tits (Parus major)?
Ágh, N, Pipoly, I, Szabó, K, Vincze, E, Bókony, V, Seress, G, Liker, A. (2020).  Biologia Futura, DOI: 10.1007/s42977-020-00024-6

Photo: Csenge Sinkovics

Since male and female offspring may have different costs and benefits, parents may use sex ratio adjustment to increase their own fitness under different environmental conditions. Urban habitats provide poorer conditions for nestling development in many birds. Therefore, we investigated whether great tits (Parus major) produce different brood sex ratios in urban and natural habitats. We determined the sex of nestlings of 126 broods in two urban and two forest sites between 2012 and 2014 by molecular sexing. We found that brood sex ratio did not differ significantly between urban and forest habitats either at egg-laying or near fledging. Male offspring were larger than females in both habitats. This latter result suggests that male offspring may be more costly to raise than females, yet our findings suggest that urban great tits do not produce more daughters despite the unfavourable breeding conditions. This raises the possibility that other aspects of urban life, such as better post-fledging survival, might favour males and thereby compensate for the extra energetic costs of producing male offspring.


Sex differences in adult lifespan and aging rates of mortality across wild mammals.
Lemaître, J., Ronget, V.,  Tidière, M., Allainé, D., Berger, V., Cohas, A., Colchero, F., Conde, D., Liker, A., Marais, G., Scheuerlein, A., Székely, T., Gaillard, J. (2020). Proceedings of the National Academy of Sciences, USA DOI: 10.1073/pnas.1911999117

In human populations, women live longer than men. While it is commonly assumed that this pattern of long-lived females vs. short-lived males constitutes the rule in mammals, the magnitude of the sex differences in lifespan and increase of mortality rate with advancing age remain to be quantified. Here, we demonstrate that, in the wild, mammalian females live longer than males but we did not detect any sex differences in aging rates. Contrary to a widespread hypothesis, we reveal that sex differences in life history strategies do not detectably influence the magnitude of sex differences in either lifespan or aging rates. Instead, our findings suggest these differences are predominantly shaped by complex interactions between local environmental conditions and sex-specific reproductive costs.

The paper is covered in international and Hungarian media: BBCCNNThe Times and NatGeoMTA, 24.hu (in Hungarian)


Biologia Futura: adaptative changes in urban populations.
Liker A. (2020).  Biologia Futura, DOI: 10.1007/s42977-020-00005-9

Cities represent novel environments where altered ecological conditions can generate strong selection pressures leading to the evolution of specific urban phenotypes. Is there evidence for such adaptive changes in urban populations which have colonized their new environments relatively recently? A growing number of studies suggest that rapid adaptations may be widespread in wild urban populations, including increased tolerance to various anthropogenic stressors, and physiological, morphological and behavioural changes in response to the altered resources and predation risk. Some of these adaptive changes are based on genetic differentiation, although other mechanisms, such as phenotypic plasticity and epigenetic effects, are also frequently involved.


Sex differences in age-to-maturation relate to sexual selection and adult sex ratios in birds.
Ancona,S., Liker, A., Carmona-Isunza, M.C. & Székely, T. (2020).  Evolution Letters, 4: 44-53, DOI: 10.1002/evl3.156

Maturation times have major fitness consequences by influencing longevity and the number of breeding opportunities, and males and females often mature at different ages. This is attributed to selection favoring divergent maturation optima among sexes, but the selective factors driving maturation bias are controversial and have remained elusive. Here, we report the most comprehensive analyses of maturation yet carried out, using data from 201 wild bird populations. We document that intense sexual competition associates with delayed maturation in the sex subjected to this selection. We also show that males mature later than females in female‐skewed populations, whereas male‐skewed environments associate with females maturing later than males. Notably, adult sex ratio, a proxy of social environment, drives sexual competition, which in turn influences maturation. Our findings have fundamental implications for both sexual selection and life‐history theory because they posit that strong sexual competition and surplus of the opposite sex promote the evolution of delayed maturation.


Városi vagányok
Ágh, N. & Seress, G. (2020). Természetbúvár, 2020/3, 28-30 [in Hungarian]

Source: WallpaperFlare

Az állatok viselkedését alapjaiban határozza meg életterük, hiszen különböző környezetben más-más tulajdonságok lehetnek előnyösek vagy éppen hátrányosak. Az ember nem is gondolná, hogy a városok milyen izgalmas új színterévé váltak az evolúciónak, ahol eldől melyik faj képes velünk együtt élni és ehhez miben kell megváltoznia. A széncinegék és a verebek alkalmazkodásának vizsgálata kutatócsoportunk egyik fő projektje és már számos érdekes viselkedésbeli és költésbiológiai változást követhettünk nyomon az ő életükben. Akit érdekel, hogy ez a két faj mit áldozott fel a városi élet oltárán, a linken elérhető ismeretterjesztő írásból megtudhatja.

— 2019 —

Higher frequency of extra-pair offspring in urban than forest broods of great tits (Parus major).
Pipoly,I., Szabó,K., Bókony,V., Hammer,T., Papp,S., Preiszner,B., Seress,G., Vincze,E., Schroeder, J. & Liker,A. (2019).  Frontiers in Ecology and Evolution, 7: 229, DOI: 10.3389/fevo.2019.00229

Occurrence of extra-pair offspring (EPO) in great tit broods at urban and forest study sites.

Urbanization increasingly changes the ecological conditions for wild animal populations, influencing their demography, reproduction, and behaviour. While studies on the ecological consequences of urbanization frequently document a reduced number and poorer body condition of offspring in urban than in non-urban bird populations, consequences for other components of reproduction are rarely investigated. Mating with partners outside the social pair-bond is widespread in birds, and although theory predicts that the occurrence of extra-pair fertilizations (EPF) may be sensitive to the altered ecological conditions of cities, the effect of urbanization on EPF is poorly known. Here we used data from two urban and two forest populations collected over three years to test whether the frequency of extra-pair offspring (EPO) in great tit broods differed between the habitats. We found that significantly more broods contained EPO in urban habitats (48.9 %) than in forests (24.4 %). In broods with EPO, the number and proportion of EPO was similar in urban and forest broods. These results suggest that females that live in urban habitats are more likely to engage in EPF than those living in forests. Urban environments may either provide more spatiotemporal opportunities to EPF because of higher breeding density, and/or enhance motivation for EPF to increased fertility in polluted environments. In addition, females with higher propensity to engage in EPF may more likely settle in urban habitats.


Parental care and the evolution of terrestriality in frogs

Vági,B., Végvári, Zs., Liker, A., Freckleton, R.P., Székely, T. (2019). Proceedings of the Royal Society B, Article ID: 20182737, DOI: 10.1098/rspb.2018.2737

Frogs and toads (Anura) exhibit some of the most diverse parental strategies in vertebrates. Identifying the evolutionary origins of parenting is fundamental to understanding the relationships between sexual selection, social evolution and parental care systems of contemporary Anura. Moreover, parenting has been hypothesized to allow the invasion of terrestrial habitats by the ancestors of terrestrial vertebrates. Using comprehensive phylogenetic analyses of frogs and toads based on data from over 1000 species that represent 46 out of 55 Anura families, we test whether parental care is associated with terrestrial reproduction and several life-history traits. See more in the paper!


Sex ratios and bimaturism differ between temperature-dependent and genetic sex-determination systems in reptiles
Bókony, V., Milne, G., Pipoly, I., Székely,T. & Liker, A. (2019). BMC Evolutionary Biology, 19: 57, DOI: 10.1186/s12862-019-1386-3

Sex-determining systems may profoundly influence the ecology, behaviour and demography of animals, yet these relationships are poorly understood. Here we investigate whether species with temperature-dependent (TSD) and genetic sex determination (GSD) differ in key demographic traits, using data from 181 species representing all major phylogenetic lineages of extant reptiles. We show that species with TSD exhibit significantly higher within-species variance in sex ratios than GSD species in three major life stages: birth or hatching, juvenility and adulthood. In contrast, sex differences in adult mortality rates do not differ between GSD and TSD species. However, TSD species exhibit significantly greater sex differences in maturation ages than GSD species.

The results support the recent theoretical model that evolution of TSD is facilitated by sex-specific fitness benefits of developmental temperatures due to bimaturism. Our findings suggest that different sex-determination systems are associated with different demographic characteristics that may influence population viability and social evolution.

Az urbanizáció és a széncinegék
Ágh, N. & Seress, G. (2019). Természetbúvár, 5:46-49 [in Hungarian]

Photo: Csenge Sinkovics

Photo: Csenge Sinkovics

A városainkban velünk élő széncinegékkel már 2012 óta foglalkozunk és egyre több érdekes vizsgálatot tudtunk már végezni velük/róluk. Mit esznek, mivel etetik fiókáikat, hogyan változik meg a szaporodási sikerük az erdőkhöz képest? Úgy tűnik, hogy habár egy város sok tekintetben rosszabb körülményeket biztosít a fiókaneveléshez, ezt a cinegék képesek kompenzálni és sikeresen együtt tudnak élni velünk. Aki kíváncsi arra, miért kezdődhet korábban a költési szezon a városokban, hogyan tudják a cinegék gyérebb táplálékkínálat mellett is sikeresen kiröptetni fiókáikat vagy éppen milyen lehetséges előnyökkel járhat mégis nekik, hogy megjelentek a városokban, a linken elérhető ismeretterjesztő írásból megtudhatja.


Great tits take greater risk toward humans and sparrowhawks in urban habitats than in forests
Vincze, E., Pipoly, I., Seress, G., Preiszner, B., Papp, S., Németh, B., Liker, A. & Bókony, V. (2019). Ethology 125(10): 686-701.

Collared dove control and sparrowhawk stimulus. Drawing: Ernő Vincze

Collared dove control and sparrowhawk stimulus. Drawing: Ernő Vincze

Urban animals often take more risk toward humans than their non‐urban conspecifics do. However, reduced vigilance toward hostile humans or non‐human predators that pose actual threat may be costly. Thus, urban animals may benefit from showing specific responses to different threat levels. We compared responses of urban and forest‐breeding great tits (Parus major) to familiar hostile and unfamiliar humans as well as one of their common predators, the sparrowhawk (Accipiter nisus). We found that urban birds were more risk‐taking toward both humans and sparrowhawk than forest birds. However, responses to sparrowhawk did not correlate with responses to humans. This suggests that higher risk‐taking of urban compared to forest‐dwelling great tits toward sparrowhawk may be threat‐specific response to lower predation risk rather than a spillover effect of increased tolerance to humans. Furthermore, birds responded similarly to unfamiliar and familiar (potentially dangerous) humans in both habitats. These findings indicate that urban birds may flexibly adjust their risk‐taking to certain, but not all, types of threat.


Malaria infection status of European Robins seems to associate with timing of autumn migration but not with actual condition
Ágh, N., Piross, I.S., Majoros, G., Csörgő, T., Szöllősi, E. (2019). Parasitology 146: 814–820.

Photo: Nigicser Ági

Photo: Nigicser Ági

Avian malaria parasites can negatively affect many aspects of the life of the passerines. Though these parasites may strongly affect the health and thus migration patterns of the birds also during autumn, previous studies on avian malaria focused mainly on the spring migration and the breeding periods of the birds. We investigated whether the prevalence of blood parasites varies in relation to biometrical traits, body condition and arrival time in the European Robin (Erithacus rubecula) during autumn migration.  Surprisingly we found that these parasites did not affect the body size or condition and showed no sex or age related variance, but the timing of autumn migration differed marginally between infected and non-infected juveniles, so that parasitized individuals arrived later at the Hungarian stopover site. This is either because avian malaria infections adversely affect the migration timing or migration speed of the birds, or or because later arriving individuals come from more distant populations with possibly higher blood parasite prevalence. This delay in timing can affect the whole migration periods, the overwinter survival and perhaps the next breeding success as well.

— 2018 —

Meta-analysis challenges a textbook example of status signalling and demonstrates publication bias
Sánchez-Tójar, A., Nakagawa, S., Sánchez-Fortún, M., Martin, D., Ramani, S., Girndt, A., Bókony, V., Liker, A., Westneat, D.F., Burke, T., Schroeder, J. 2018. eLife 7:e37385.

The status signalling hypothesis aims to explain within-species variation in ornamentation by suggesting that some ornaments signal dominance status. Here, we use multilevel meta-analytic models to challenge the textbook example of this hypothesis, the black bib of house sparrows (Passer domesticus). We conducted a systematic review, and obtained primary data from published and unpublished studies to test whether dominance rank is positively associated with bib size across studies. Contrary to previous studies, the overall effect size (i.e. meta-analytic mean) was small and uncertain. Furthermore, we found several biases in the literature that further question the support available for the status signalling hypothesis. We discuss several explanations including pleiotropic, population- and context-dependent effects. Our findings call for reconsidering this established textbook example in evolutionary and behavioural ecology, and should stimulate renewed interest in understanding within-species variation in ornamental traits.


Sex-biased breeding dispersal is predicted by social environment in birds
Végvári, Z., Katona, G., Vági, B., Freckleton, R., Gaillard, J., Székely,T., Liker,A. 2018. Ecology and Evolution 13: 6483-6491.

Sex‐biased dispersal is common in vertebrates, although the ecological and evolutionary causes of sex differences in dispersal are debated. Here, we investigate sex differences in both natal and breeding dispersal distances using a large dataset on birds including 86 species from 41 families. Using phylogenetic comparative analyses, we investigate whether sex‐biased natal and breeding dispersal are associated with sexual selection, parental sex roles, adult sex ratio (ASR), or adult mortality. We show that neither the intensity of sexual selection, nor the extent of sex bias in parental care was associated with sex‐biased natal or breeding dispersal. However, breeding dispersal was related to the social environment since male‐biased ASRs were associated with female‐biased breeding dispersal. Male‐biased ASRs were associated with female‐biased breeding dispersal. Sex bias in adult mortality was not consistently related to sex‐biased breeding dispersal. These results may indicate that the rare sex has a stronger tendency to disperse in order to find new mating opportunities. Alternatively, higher mortality of the more dispersive sex could account for biased ASRs, although our results do not give a strong support to this explanation. Whichever is the case, our findings improve our understanding of the causes and consequences of sex‐biased dispersal. Since the direction of causality is not yet known, we call for future studies to identify the causal relationships linking mortality, dispersal, and ASR.


Personality assortative female mating preferences in a songbird
Pogány, Á., Vincze, E., Szurovecz, Z., Kosztolányi, A., Barta, Z., Székely, T., Riebel, K. 2018. Behaviour, 155: 481-503.

Drawing by: Ernő Vincze

Drawing: Ernő Vincze

Consistent individual behavioural differences (‘animal personalities’) are documented across a variety of animal taxa. Sexual selection, especially assortative mating has been suggested as a possible mechanism contributing to the maintenance of different personality types within populations but little is known about non-random pair-formation with respect to personality traits in unconstrained choice tests. We here tested whether female mating preferences were non-random with respect to male and female neophobia in zebra finches (Taeniopygia guttata), an important avian model of mate choice and animal personality research. Male and female neophobia was assessed by attaching novel objects to birds’ feeders. Females’ mating preferences were tested with randomly assigned, unfamiliar males in a four-way choice apparatus. Females associated most with males with neophobia scores similar to their own. These results provide evidence that mating preferences and personality traits can covary, supporting evolutionary scenarios of assortative mating contributing to the maintenance of personality traits.


Obtaining accurate measurements of the size and volume of insects fed to nestlings from video recording
Sinkovics,Cs., Seress,G., Fábián,V., Sándor,K. & Liker,A. 2018. Journal of Field Ornithology, 89(2):165-172

Plasticine caterpillar
Photo: Csenge Sinkovics

In this paper we examined the accuracy and repeatability of estimates of the size of food items from video recordings. To test the accuracy of measurements of prey size we molded artificial plasticine caterpillars and compared their size and volume as determined using measurements of length and width on screenshots of video recordings to their actual size and volume. We also studied within‐ and among‐observer repeatability of measurements of the size and volume of actual prey items delivered to nestlings by adult Great Tits. We found that observers were able to accurately measure prey size and determine volume, with high agreement between the actual size and volume of plasticine caterpillars and the size and volume as determined from measurements made on screenshots from video recordings. In addition, within‐ and among‐observer repeatability were also high. Overall, our results suggest that the size of prey items delivered to nestlings by adults in video recordings can be accurately measured and those measurements, in turn, can be used to accurately determine the volume of those insect prey.

Impact of urbanization on abundance and phenology of caterpillars and consequences for breeding in an insectivorous bird
Seress,G., Hammer,T., Bókony,V., Vincze,E., Preiszner,B., Pipoly,I., Sinkovics,Cs., Evans,K.L. & Liker,A. 2018. Ecological Applications,  28(5):1143-1156

Winter moth – Operophtera brumata
, a common species in our study system. Photo: https://www.flickr.com/photos/annetanne/4621971435

In this paper we studied a tri-trophic system of trees – phytophagous insects (caterpillars) – insectivorous birds (great tits Parus major) to assess how urbanization influences i) the phenology of each component of this system, ii) insect abundance and iii) avian reproductive success. We use data from two urban and two forest sites in Hungary, collected over four consecutive years. Despite a trend of earlier leaf emergence in urban sites there is no evidence for an earlier peak in caterpillar abundance. Thus the earlier breeding of urban bird populations is not associated with an earlier peak in caterpillar availability. We also found striking differences in the seasonal dynamics of caterpillar biomass between habitat types with a single clear peak in forests, and several much smaller peaks in urban areas. Caterpillar biomass was 8.5 – 24 times higher in forests compared to urban areas during the first brood’s chick-rearing period. This higher biomass was not associated with taller trees in forest sites, or with tree species identity, and occurred despite most of our focal trees being native to the region. Urban great tits laid smaller clutches, experienced more frequent nestling mortality from starvation, reared fewer offspring to fledging age, and their fledglings had lower body mass. Our study strongly indicates that food limitation is responsible for lower avian reproductive success in cities, which is driven by reduced availability of the preferred nestling diet, i.e. caterpillars, rather than phenological shifts in the timing of peak food availability.

— 2017– 

Univerzális, ivarhatározáshoz használt CHD1 markerek alkalmazhatósága különböző madár rendekben
Ágh, N., Kovács, Sz., Nemesházi, E. & Szabó, K. 2017. Magyar állatorvosok lapja, 140: 47-59.

Photo: Krisztián Szabó

Photo: Krisztián Szabó

Defining the sex of individual birds can be crucial for scientific studies and captive breeding, as well. However, many bird species (and almost all nestling) can only be sexed via molecular methods. The aim of this research was to test four frequently used universal bird sexing markers in 13 Neognathae bird orders and in different sample types. These markers (P2/P8, 2550F/2718R, CHD1-i16 and CHD1-i9) amplify fragments of intronic regions of the CHD1-Z and CHD1-W genes. Our results confirm the universality of these primer pairs in most avian orders, but their application needs some consideration.


Haematospirillum and insect Wolbachia DNA in avian blood
Hornok, S., Ágh, N., Takács, N., Kontschán, J., & Hofmann-Lehmann, R. 2017. Antonie van Leeuwenhoek, 1-5., DOI: 10.1007/s10482-017-0961-0, 2017

Photo: Dr. Csörgő Tibor

Photo: Dr. Tibor Csörgő

In this study, blood samples of 259 Acrocephalus spp. warblers were molecularly analysed for Anaplasmataceae and Rhodospirillaceae based on PCR amplification of 16S rRNA gene fragments. We founded the first molecular evidence for the occurrence of Haematospirillum jordaniae in the blood of any vertebrate other than human. Another bird blood sample yielded a Wolbachia sequence, closely related to a moth endosymbiont. This is the first finding of insect Wolbachia DNA in the circulatory system of birds, which can be explained either by the inoculation of wolbachiae by blood-sucking vectors, or passing of Wolbachia DNA from the gut into the blood of this insectivorous bird species.


Climate-driven shifts in adult sex ratios via sex reversals: the type of sex determination matters
Bókony V., Kövér Sz., Nemesházi E., Liker A., Székely T. 2017. Philosophical Transactions of the Royal Society B: Biological Sciences, 372: 20160325, 2017

Photo: Bálint Üveges

Sex reversals whereby individuals of one sex develop the phenotype of the opposite sex occur in amphibians, reptiles and fish. Warming of global climate predicts that such sex reversals are becoming more common. We show using theoretical models that XX/XY and ZZ/ZW sex-determination systems can respond differentially to temperature-induced sex reversals. Analyzing data from the literature, we find that the adult sex ratio in natural amphibian populations shifted towards males in ZZ/ZW species over the past decades, but did not change in XX/XY species. Our results highlight the need for understanding the interactions between genetic and environmental sex-determining mechanisms.


Effects of capture and video-recording on the behavior and breeding success of Great Tits in urban and forest habitats
Seress, G., Vincze, E., Pipoly, I., Hammer, T., Papp, S., Preiszner, B., Bókony, V. & Liker, A. 2017. Journal of Field Ornithology, 88(3): 299-312, 2017

Photo: MTA-PE Evolutionary Ecology Research Group

We studied the effects of both capturing, weighing and measuring, and taking a blood sample, and the presence of video-cameras on the behavior of male and female Great Tits breeding in urban and forest habitats. Using a 2 x 2 block design, we compared the behavior and breeding success of parents that either were or were not captured on their nests a few days before behavioral observations, and of parents that either were or were not habituated to the presence of a concealed video-recorder mounted on nest boxes. We found no significant effects of habituation to the camera on bird behavior, but males captured in their nest boxes were more vigilant and hesitated longer before entering nest boxes, and also had slightly lower provisioning rates than males that had not been captured. Captured females also tended to be more vigilant than non-captured females, but their provisioning rates were not affected. In males, capturing also influenced the behavior of their non-captured mates. We found no difference in the effects of capture in urban and forest habitats, and our treatments also had no effect on the mass, size, and survival of nestlings until fledging. Our results suggest that, for Great Tits, being captured results in sex-dependent behavioral effects that can last for at least several days.


Does urbanization affect predation of bird nests? A meta-analysis
Vincze, E., Seress, G., Lagisz, M., Nakagawa, S., Dingemanse, N.J. & Sprau, P. 2017. Frontiers in Ecology and Evolution, DOI: 10.3389/fevo.2017.00029

Photo: © Jack Jeffrey Photography

Photo: © Jack Jeffrey Photography

Urbanization can affect interspecific interactions such as predation on bird nests. Using a formal meta-analytical approach, we carried out a systematic literature review to test whether predation on natural and artificial bird nests increased or decreased with habitat urbanization. We found that the effect was highly heterogeneous among studies, due to contrasting results between studies that used artificial nests and those that used natural nests. For artificial nests, survival rate tended to decrease with increasing urbanization, whereas for natural nests, survival was higher in more urbanized habitats. This discrepancy suggests that the direction of the relationship between urbanization and nest predation is likely to depend on the methodology of the study.

Innovative females are more promiscuous in great tits (Parus major)
Veronika Bókony, Ivett Pipoly, Krisztián Szabó, Bálint Preiszner, Ernő Vincze, Sándor Papp, Gábor Seress, Tamás Hammer  & András Liker. 2017. Behavioral Ecology, DOI: 10.1093/beheco/arx001

Photo: Csenge Sinkovics

We found that innovative great tit females are prone to cuckold their mates. Innovative problem solving can be important to animals for survival and reproduction in nature, yet we found no evidence that females mated to males with poor problem-solving performance compensate for poor male quality by obtaining superior genes for their offspring from other males via cuckoldry. Instead, females’ infidelity increased with their own innovativeness.

Status signalling in male but not in female Eurasian Tree Sparrows Passer montanus
F Mónus, A Liker, Zs Pénzes, Z Barta. 2017. Ibis 159: 180-192, 2017

Photo: András Liker

Photo: András Liker

We investigated the outcomes of aggressive encounters in foraging flocks of free-living Tree Sparrows, and assessed whether throat patch size and measurements of body size predicted fighting success. We found that male throat patch size predicted fighting success against both male and female opponents. However, female throat patch size did not correlate with fighting success against either sex. Among the morphological traits studied, wing length was the best predictor of fighting success in females. Our findings suggest a status signalling function of throat patch size in males but not in females.

Problem-solving performance and reproductive success of great tits in urban and forest habitats
B Preiszner, S Papp, I Pipoly, G Seress, E Vincze, A Liker, V Bókony.
Animal Cognition, 20: 53–63, 2017

Photo: Bálint Preiszner

Photo: Bálint Preiszner

Success in problem solving, a form of innovativeness, can help animals exploit their environments, and recent research suggests that it may correlate with reproductive success. Innovativeness may have a greater positive effect on fitness in more urbanized habitats. We tested this idea in great tits by measuring their problem-solving performance in two tasks. Urban pairs were significantly faster problem-solvers in both tasks. In one of the tasks positive fitness consequences were found, though irrespectively of urbanization. Neophobia, sensitivity to human disturbance, and risk taking in the presence of a predator did not explain the relationships of problem-solving performance either with habitat type or with reproductive success. The reproductive benefit of innovativeness in great tits is similar in urban and natural habitats, implying that problem-solving skills may be enhanced in urban populations by some other benefits or reduced costs.

— 2016 —

Habituation to human disturbance is faster in urban than rural house sparrows
Ernő Vincze, Sándor Papp, Bálint Preiszner, Gábor Seress, Veronika Bókony & András Liker. 2016. Behavioral Ecology 27: 1304-1313, 2016

Urban house sparrows flee from humans from shorter distances. Drawing: Ernő Vincze

Urban house sparrows flee from humans from shorter distances. Drawing: Ernő Vincze

Urban birds need to reduce their fear from humans to tolerate their presence. We show that urban house sparrows in the field have shorter flight initiation distances from humans than rural ones, but in captivity they initially show similar fear from humans. However, urban sparrows show faster habituation, i.e. decrease their fear response to repeated human disturbance faster. This difference may play a role in why certain birds exploit urban habitats better than others.

— 2015 — 

The evolution of parental cooperation in birds.
Vladimír Remeš, Robert P. Freckleton, Jácint Tökölyi, András Liker & Tamás Székely. 2015. Proceedings of the National Academy of Sciences USA 112: 13603–13608

Phylogenetic distribution of parental cooperation in birds included in this study. Figure shows parental cooperation (tall black bars refer to high cooperation) and phylogenetic reconstruction along branches.

Phylogenetic distribution of parental cooperation in birds included in this study. Figure shows parental cooperation (tall black bars refer to high cooperation) and phylogenetic
reconstruction along branches.

Parents in many animal species care for their offspring. In some species males care more, in other species females care more, whereas in still other species the contribution of the sexes is equal. Using the most comprehensive analyses of parental care to date, here we show that parents cooperate more when sexual selection is not intense and the adult sex ratio of males to females is not strongly skewed. However, the degree of parental cooperation is unrelated to harshness and predictability of the ambient environment during the breeding season. These results suggest that several parental strategies may co-exist in a given set of ambient environment.

The genetic sex-determination system predicts adult sex ratios in tetrapods.
Ivett Pipoly, Veronika Bókony, Mark Kirkpatrick, Paul F. Donald, Tamás Székely & András Liker. Nature 527,91–94, 2015

he European green lizard (Lacerta viridis) has WZ sex chromosomes, like some other reptiles, some amphibians and all birds (photo: Liker A.)

The European green lizard (Lacerta viridis) has WZ sex chromosomes, like some other reptiles, some amphibians and all birds (photo: A. Liker)

Recent theoretical and empirical work shows that adult sex ratio (ASR, proportion of males in the population) has a major influence on pair bonds, mating systems and parental care, although the causes of ASR variation have remained obscure. Here we show for the first time that ASR is predicted by the type of genetic sex-determination system in amphibians, reptiles, birds and mammals: the heterogametic sex is underrepresented in the population. Using novel population-genetic models, we also explore various genetic mechanisms that can mediate the effects of sex-determination systems on ASR.

Distribution of sex bias in pre-hatching and post-hatching care in birds (-1: female only care, 0: equal male and female care, 1: male only care).

Distribution of sex bias in pre-hatching and post-hatching care in birds (-1: female only care, 0: equal male and female care, 1: male only care).

Sex differences in parental care: Gametic investment, sexual selection, and social environment.
A. Liker, R.P. Freckleton, V. Remeš & T. Székely. 2015. Evolution 69: 2862-2875

Using detailed behavioural data of nearly 800 birds, we confirm theoretical models proposing that parental sex roles are predicted by sexual selection and the social environment, but are unrelated to gametic investment of the sexes.

Using the BirdTree.org website to obtain robust phylogenies for avian comparative studies: A primer.
Rubolini, D., Liker, A., Garamszegi, L.Z., Møller, A.P. & Saino, N. 2015. Current Zoology 61: 959-965


A BirdTree.

Comparative studies require accounting for shared evolutionary history. The online publication of the phylogeny of extant bird species (www.birdtree.org) now allows biologists to rapidly obtain phylogenetic trees for any set of species to be incorporated in comparative analyses. We discuss methods to use BirdTree tree sets for comparative studies, either by building a consensus tree that can be incorporated into standard comparative analyses, or by using tree sets to account for the effect of phylogenetic uncertainty.

Does innovation success influence social interactions? An experimental test in house sparrows.
Preiszner, B., Papp, S., Vincze, E., Bókony, V. & Liker, A. 2015. Ethology 121: 661–673

Large and bright birds

Larger and more innovative birds get more attacks. Drawing: Ernő Vincze

Individuals may benefit from the presence of an innovative group-mate because new resources made available by innovators can be exploited. In this study we conducted an experiment to investigate whether individuals behave differently towards their innovative and non-innovative flock-mates in the house sparrow. Our experimental results suggest that some common social interactions are not influenced by the apparent problem-solving ability of the group-mates, however birds may use subtle cues to to assess the problem-solving ability of their companions.

A comparison of problem-solving success between urban and rural house sparrows.
Papp, S., Vincze, E., Preiszner, B., Liker, A. & Bókony, V. 2015. Behavioral Ecology and Sociobiology 69: 471-480.

Problem-solving box

One of the problem-solving tasks of the experiment. Photo: Veronika Bókony

Behavioral flexibility is an important component of adaptation as it can help animals to exploit new or diverse habitats. Due to the abundance of novel objects and resources provided by humans, urban environments may select for better problem solving skills in wild animals. To test this idea, we compared the performance of house sparrows from urban and rural habitats in four novel problem solving tasks during which they had to acquire food from different feeders. These results demonstrate that problem solving success shows both individual consistency and context dependence, and whether or not urban individuals are more innovative across various situations.

Habitat urbanization and its effects on birds.
Seress, G. & Liker, A. 2015. Acta Zoologica Academiae Scientiarum Hungaricae 61: 373-408.

This review focuses on the bottom-up and top-down regulation of urban bird communities. In our work we also discuss and illustrate the mechanisms which generate and uphold the changes in urban avian communities, and affect birds’ physiology, behaviour, morphology and breeding success.

One of the latex masks used in the experiment (alias: EV camouflaged)

One of the latex masks used in the experiment (alias: EV disguised)

Does urbanization facilitate individual recognition of humans by house sparrows?
E. Vincze, S. Papp, B. Preiszner, G. Seress, A. Liker & V. Bókony. 2015. Animal Cognition 18: 291-298

Individual recognition of humans may be beneficial for animals living in an anthropogenic environment, but little is known about how this ability changes along the urban gradient. In this study we captured house sparrows from differently urbanized habitats and manipulated their experience (hostile or not) associated with humans with different faces (masks). Surprisingly, we found that rural sparrows adjusted their behaviour more to the percieved dangerousness of the person than their urban conspecifics.

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