Bringing tits to the country in summer?
As cities expand, the environment for many wildlife is changing. Researchers at the University of Innsbruck are using great and blue tits to study how their food and the green spaces in and around the city influence the behavior and health of the animals.
If there is free food somewhere, everyone is happy to come. This applies not only to free beer offers for humans, but also for wildlife that forage for food in human settlements. The best-known examples are birdhouses and feeders that attract many birds. Using the example of blue tits and great tits, a team from the University of Innsbruck is investigating how strongly such food offers influence the small-scale migration of the animals.
The background is that the cities of our world are getting bigger and this urbanization also has an impact on the life of wild animals. Marion Chatelain and Michael Traugott from the Institute of Zoology compare the entire gradient of the city center, residential areas, industrial areas, suburbs, rural and forest areas – in Innsbruck and the towns of Völs, Neugötzens, Mutters, Natters, Lans, Sistrans, Aldrans, Rum and Ampass. “Previous studies usually collected one point in the city with one point in the country,” says Marion Chatelain, who is leading the project as part of her Lise Meitner grant from the Austrian Science Fund FWF. But the changes in landscape and climatic conditions are much smaller and can also vary within a city, if you think of places as different as Hofgarten, Innufer or Olympisches Dorf. In addition, the vegetation in cities is often more exotic than outside. “We caught almost 500 blue and great tits at 180 locations in and around Innsbruck and were able to tag them individually,” says Chatelain. Catching, ringing and measuring burden the birds for only a few minutes. With alarm calls from the tape, the tits are lured into the bushes, where they get caught in animal-friendly nets. The zoologists gently “pluck” the tits from the net, quickly take all the samples and data, put the tits in a small cage where they can make a birdie and then release them again. The researchers learn from the faecal samples what the animal has eaten, from the feathers what metal and pollutant concentrations were in its environment, and from the muscle mass how well developed the animal is.
Insects versus fat balls
“Tits are insectivores, but they’re willing to take on urban food like seeds, fat balls, and the like,” says Chatelain. Since the birds mainly need insects (protein) to raise their young, the researchers assume that the tits come more to the cities in winter to fetch the readily available food, but migrate to the countryside in spring and summer to find theirs To provide chicks with the best insect food.
The first step was to determine the variety and abundance of insects in and around the city. “In Innsbruck there are sometimes even more insects than in the countryside,” says Chatelain. Some species benefit from urbanization, such as aphids, booklice and flies. Other groups of animals are less common in the city, e.g. B. Spiders. “In Innsbruck, however, the diversity of species was lower than in the surrounding area,” says Chatelain, who is currently waiting for the results of the faecal samples. The DNA analysis will reveal which insects and seeds are preferred by tits in which season.
The isotope determination and the metal concentrations from the plumage have not yet been completed either. Chatelain has already shown that the concentration of zinc in bird feathers increases as the environment becomes more urban. “The environmental conditions after the last moult of the birds are stored in the feathers: This allows us to estimate where the animal was.” Some specimens even come to us in the summer from Lithuania or Poland, where tits live as migratory birds. Local specimens almost all remain in Austria throughout. “We are dependent on the cooperation of the population: the tits in our study have colored rings on their legs. Anyone who sees such birds can report it to us so we can determine migratory behavior.”
Register tits with colored rings in and around Innsbruck: [email protected]
(“Die Presse”, print edition, June 11, 2022)