The global land surface covered by cities is expected to triple between 2000 and 2030. Urbanisation is a major driver of environmental changes, including landscape fragmentation and food availability modifications. Nonetheless, cities are also inhabited by plants and animals, which have great ecological importance and social value. How does urbanisation affect wildlife in cities? Although timely, this question remains largely unanswered. In particular, our knowledge on how food availability and patchiness in the cities affect movements over time is at its infancy. Providing wild urban animals with food (e.g. seeds) during winter became a very common practice. This extra food particularly benefits birds that consequently cope better with harsh conditions in winter. For this reason, we hypothesize that cities are optimal wintering grounds and would attract individuals from outside the city or from areas with few human settlements within the city. On the contrary, birds produce less offspring and those offspring are of lower quality in cities compared to less disturbed environments, likely because of differences in the availability of essential nutrients during growth. Therefore, we assume that cities are sub-optimal breeding grounds. Altogether, the changes in cities’ ability to sustain bird populations over the year is likely to generate movements within the city and the surrounding environment.
The great tit Parus major and the blue tit Cyanistes caeruleus are flagship animals that are now becoming reference species to study the ecological and evolutionary effects of urbanisation. In this project we will investigate how great and blue tit populations respond to urbanisation employing a gradient of urbanisation in Innsbruck and its surroundings. Specifically, we will study the effects of urbanisation on:
1) food availability for omnivorous bird species (i.e. arthropod availability in trees and bushes and human-provided food), 2) great and blue tit diet by identifying the prey DNA in their faeces, and 3) great and blue tit movements within the city and between the city and its surroundings. For the latter a novel combination of re-catching data and the metal pollution signature in bird feathers, which correlated with urbanisation level, will be used. Long-distance migration will also be investigated using feather isotopic signature.
This project will improve our understanding of how animals move within cities in response to food availability and therefore answer key questions in the new field of urban ecology. Compared to previous studies, it takes into account the fine-scale structure of urban settlements to better catch the variability in urban habitat quality. Moreover, it relies on innovative and non-invasive methods in molecular and chemical ecology to efficiently measure diet and movements of birds in the urban environment.
Updates on the project can be found at: bit.ly/kohl-und-blaumeisen
