The impacts of habitat urbanization on birds’ breeding biology, demography, behavior and genetics

Urbanization is one of the major threats to global biodiversity. Compared to the more natural habitats, the environmental and ecological conditions (e.g. microclimate, food availability, predation risk or disturbance) are substantially altered in urban areas, exerting diverse effects on the diversity, individual and population level characteristics of urban wildlife. Our aim is to explore and understand these effects using the Great tit (Parus major) as a model species. To achieve this we are working at several urban and forest locations and also along urban-to-rural gradients in Hungary, utilizing an ongoing monitoring system (started in 2013) that is based mostly on colour ringed (i.e., individually identifiable) individuals. The project is structured in several main topics, introduced below in brief.

First, we are measuring reproductive success and phenology, nestling and adult survival, and also recruitment to explore the long-term differences, trends and year-to-year fluctuations in urban and non-urban great tit populations. By combining these parameters we also aim to build demographic models to understand the dynamics and functioning of urban and forest bird populations.

Second, to better understand the ecological drivers and their relative importance in urban and non-urban environments, we also study the relationships between birds’ breeding success components or morphological traits (e.g. morphology, feather structure) and local climate (e.g. temperature, extreme meteorological events) or food availability during the breeding season (e.g. caterpillar biomass in birds’ environments and nestling food composition).

Third, we also study various components of birds’ behaviour that might be affected by urban environments, like problem-solving, explorative and nest defending behaviour, risk-taking towards humans and predators, or the behavioural impacts of such commonly used techniques in field ornithology, like individuals’ capture on their nests or the presence of a small video camera on the nest box. To achieve this we use field and lab experiments as well, and our earlier studies also involved one of the most widespread urban bird, the House sparrow (Passer domesticus), as a model species.

Finally, we use genetic tools to study e.g. the frequency of extra-pair paternity or offspring sex ratio in urban and non-urban great tit populations. Additionally, we also aim to investigate the genetic background of urban birds’ ‘behavioural phenotype’ by exploring associations between the components of behaviour, like tolerance towards human disturbance or problem-solving success, and the frequency of certain candidate gene loci (DRD4, SERT) that might play important roles in the development of these traits.

Some key publications:

  • 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
  • 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, DOI: 10.1002/eap.1730
  • 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
  • Problem-solving performance and reproductive success of great tits in urban and forest habitats. Preiszner B., Papp S., Pipoly I., Seress G., Vincze E., Liker A., Bókony V. 2017. Animal Cognition. DOI: 10.1007/s10071-016-1008-z

Phylogenetic comparative studies

Fig 1. Variation in genetic sex determination system and adult sex ratio across tetrapod vertebrates (Pipoly et al. 2015).

Adult sex ratio (ASR) is one of the central demographic properties of populations. We study the causes and consequences of ASR variation among species. We showed that interspecific differences in ASR is related to the type of genetic sex determination systems in tetrapods (Fig 1), and to sex differences in adult mortality rates and age of maturation in birds. We also found that the ASR is correlated with various reproductive traits, like mating system, parental care and the frequency of divorce in birds (Fig 2).


Fig 2. The relationships between adult sex ratio and components of sex roles in shorebirds (Liker et al. 2013).

Currently we are extending these lines of research and test further how sex ratios may be regulated by demographic processes and how ASR may influence reproductive behaviour in other vertebrate taxa.

We also use large scale comparative analyses to investigate the diversification of components of reproductive sex roles (i.e. mating systems and parental care behaviour) across vertebrates, and to find ecological and life history factors that may play a role in their evolutionary changes. For example, we analysed how reproductive investment, sexual selection and climatic conditions are related to the forms and sexual differences of parental care in birds and amphibians (Fig 3), and are conducting similar studies in other vertebrates like fish and reptiles.


These projects are based on longterm collaborations with several research institutions including University of Bath, University of Sheffield, University of Lyon, and University of Debrecen.

Fig 3. Phylogenetic distribution of nest building and attendance by male and female frogs (Vági et al. 2020).

Some key publications:

  • Liker A, Freckleton RP, Székely T 2013. The evolution of sex roles in birds is related to adult sex ratio. Nature Communications 4: Article number 1587.
  • Pipoly I, Bókony V, Kirkpatrick M, Donald PF, Székely T, Liker A 2015. The genetic sex determination system predicts the adult sex ratio in tetrapods. Nature 527: 91–94.
  • Vági B, Végvári Z, Liker A, Freckleton RP, Székely T 2020. Parental care forms are predicted by climatic and social environments in Anura. Global Ecology and Biogeography 29: 1373-1386,

Integrative approach to unravel demographical and behavioural drivers of male-biased sex ratio and sex-role reversal in the Pheasant-tailed jacana

In a few bird species the sex roles are reversed, meaning the females compete for access to males and mate with several males while these latter incubate and care for the offspring. How this mating system happens in these species? Previous research tried to disentangle possible ecological drivers using comparative approach but most of them stressed that we lack crucial information about these species. This project tests and integrates current hypotheses of sex-role and mating system evolution by linking demographic patterns, behavioural strategies and environmental constraints using the Pheasant-tailed jacana as a model species. Through a holistic approach we intend at disentangling different selective patterns leading to such a specific mating system. This project is structured in 4 main topics:

First, this project aims at finding out how a male-biased adult sex ratio is created in the population. We measure important demographic parameters to understand the age and sex-dependent variation leading to a male-biased ASR in a polyandrous and sex-role reversed species.

A second part of the project focusses on the inter- and intra-individual behavioural differences within the population and over time and test how this variation is shaped by environmental and demographic conditions.


In a third part of the project, we aim at understanding how males avoid extra pair fertilisation when sperm competition is high: e.g. egg removal, mate guarding.


Finally, we focus on the consequences, the degree and strength of a sexual selection which is stronger on female than on males in this species. We aim at linking the strength of sexual selection (through sex differences in reproductive success) with sex-specific survival, investment in secondary sexual traits and sexual size dimorphism from the perspective of competing females.

This project is in collaboration with Khon Kaen university (Thailand) where the monitored Pheasant-tailed jacana population is living.

Prospective students interested in this project should contact Dr. Nolwenn Fresneau: nolwenn.fresneau[at]

This project is founded by a NKFIH OTKA Postdoctoral excellence program grant (2020-2023)