Kestrels in the City

Common kestrel falco tinnunculus (Image: Wikimedia Commons)
Common kestrel falco tinnunculus
(Image: Wikimedia Commons)

With the help of the public, researchers from the University of Vienna, Austria, have found out that the Eurasian kestrel can be “seduced” by the city lights, but this decision comes at a cost, with lower reproductive success and a poorer diet.

Urbanization is a global event that is invading natural habitats, inevitably leading to a decrease in biodiversity. However, rather surprisingly, this is actually creating new habitats for some species. “Most city dwelling birds are exploiting human resources, like garbage dumps (for example gulls), feeders (granivore birds), or artificial nest sites/nest boxes for cavity breeders”, said Petra Sumasgutner, lead author in the study. “If a species can exploit the urban environment is therefore very much connected to what it needs in its natural habitat”.

In particular, the Eurasian kestrel (Falco tinnunculus) is frequently associated with urban landscapes, and Vienna seems to be a popular destination for these birds. For years, Sumasgutner observed kestrels building their nests in small cavities, abundant in old historic buildings, and her scientific curiosity led to further questions about how this is affecting the species.

To find these much wanted answers, her team decided to investigate occupied nest sites in and around Vienna, along a gradient of urbanization from least covered to most covered by buildings. Since coverage of the entire city of Vienna looking for kestrels required many watchful eyes, researchers enlisted the help of volunteers to help them in this search over 3 years. “It was a lot of effort to work with the media and the general public, but it was also a lot of fun. Especially the collaboration with the chimney sweepers and the firefighters was the best”, said Sumasgutner.

It turned out that, although the availability of breeding cavities attracts many birds to highly urbanized areas, city life is not all that’s cracked up to be for kestrels. Birds nesting in the city were more likely to abandon the nest, resulting in lower hatching rates and smaller fledged broods than those breeding in the outskirts. The authors suggest this effect may be a consequence of a forced change in the bird’s diets while staying in the city, as their natural ability to hunt rodents on the ground needed to shift to find small birds instead.

At first, it may seem these city-dwelling raptors are exploiting the urban environment, but a closer look reveals what the authors called an “ecological trap”, with unexpected costs both in terms of reproductive success and prey availability. When asked about the future of kestrels in the city, Sumasgutner’s answer is clear: “not at all in the inner-city”. After observing how kestrels can also nest in purpose-built nest boxes, the author suggested using “the same mechanism which attracts kestrels to breed in highly urbanized areas to actually lure them in a more suitable habitat, like buildings around larger city parks or also the suburban area of Vienna”.

Maybe this could be their next citizen science project, again enrolling the help of the public to save the kestrel. After all, “I would work again in a citizen science project”, concluded Sumasgutner.

Interested in kestrel citizen science projects?  Monitor American kestrels with the American Kestrel Partnership or the Massachusetts Audubon American Kestrel Monitoring Project.

Dr. Alex Reis is a freelance science writer, with a particular expertise in the field of biology and genetics. She holds a degree and MSc in Animal Science, topped up with a PhD in Embryology. In a ‘previous life’ as a researcher, she worked in the field of cell and molecular biosciences and published various scientific manuscripts including in Nature. Nowadays, however, she spends most of her time reading and writing science articles for several news outlets. Recent work includes articles published in The Munich Eye, Decoded Science, United Academics Magazine, BitesizeBio and Science NOW. After moving around the UK for a while, she now lives in the Highlands of Scotland. When not working, she can be found trying to get friendly with the ‘locals,’ from deer to seals, otters or even sea eagles.

Categories: Animals, Birds, Citizen Science, Ecology & Environment, Nature & Outdoors