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Social life in the city: how urbanization affects cooperation and competition among social birds

Periodic Reporting for period 1 - urbanbird (Social life in the city: how urbanization affects cooperation and competition among social birds)

Reporting period: 2018-04-01 to 2020-03-31

The action Social life in the city: how urbanization affects cooperation and competition among social birds looks at how urbanization affects behaviour and population dynamics of birds in the Netherlands.
Human induced environmental change like urbanization, involves a drastic change of the environment and will affect the abundance of resources and thus the costs and benefits of how individuals cooperate and compete for resources. However, how urbanization affects such social behaviour remains unknown. It is important to better understand this, since social behaviours are crucial for an individual’s fitness. Thus, factors affecting social behaviour will have large implications for the dynamics and persistence of populations, and improving knowledge on this topic will help to predict the effects ongoing urbanization will have on species and biodiversity.
The aims of this project were to examine the impacts of urbanization on population dynamics and social behaviour of birds. In addition, a parallel goal of this reintegration fellowship was for the Fellow to re-enter the European academic system and develop skills required to initiate an independent research group.
Data was collected through a citizen science project whereby trained volunteers catch, measure and band birds in their backyard twice a month using mist nets. Captured birds were aged and sexed based on plumage characteristics, and morphometric measurements were taken, including body weight, wing length and fat score. Two gradients of urbanisation were defined: the distance to the city border and the percentage impervious surface, which were calculated within a 200m radius for each of the >200 catch locations using GIS. Survival was analysed using capture-recapture models, accounting for variation in recapture probability. Our results show that survival responses to urbanisation varied among species, with four species showing higher survival in more urbanised areas and one species showing lower survival. In addition, we examined whether there were any non-lethal effects of urbanisation by examining body mass and size. Since urbanisation might affect mass and size, whereas at the same time larger individuals are also expected to be heavier, structural equation models were used allowing for the simultaneous estimation of effects of urbanization on mass and size. Results showed that most species had relatively lower body weight in more urban areas, whereas size did not vary with the degree of urbanization. These results were presented at an international ecology conference and a paper detailing these results is in preparation.
Further examination of the effect of urbanization on various biometry measurements showed that particularly more social species (house sparrows) show consistent associations with urbanization, with urban individuals being smaller, leaner and having lower body fat, suggesting lower competition in urban areas (BSc thesis). Current work aims to disentangle what aspect (i.e. buildings, roads or distance to city edge) of urbanization is the most important driver of variation in biometry (BSc thesis).
The effect of urbanization on social behavior was examined by conducting behavioural observations on house sparrows (Passer domesticus) at feeding tables in urban and rural areas. This work was implemented within the BSc course in Animal Ecology, whereby students learned how to specify and collect behavioural data in the field. Preliminary results show that urban house sparrows are less efficient foragers, as they spent more time scanning their surroundings when on a feeding table. This work will be continued in further projects.
The Fellow was able to improve her teaching and supervision skills and gain valuable experience in course coordination. Following the Action, the Fellow has obtained a tenure track position at the host institute allowing her to further develop her own research group.
Although urbanization has been suggested to have negative impacts on species and populations, some species actually thrive, suggesting we cannot generalise across species. Indeed, our work shows that some species seem to benefit, whereas others suffer. Possibly because of variation in how individuals compete and cooperate. This implies that future predictions about the effects of ongoing urbanization will need to consider species characteristics and possibly even which aspects of urbanization are expected to change most.
A colour banded house sparrow caught in mist net. Credit: Bram Ubels