We study animal behaviour, ecology and evolution, focusing 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:

— 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. 2109. 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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