Backyard feeders may be attracting more than songbirds, new studies suggest.
The backyard feeder is a source of delight for birdwatchers from Brussels to Brisbane, but a pair of studies suggests that people are attracting more than songbirds. They’re also attracting hawks and other predators who have moved to the city, and find the feeders make their own bird-hunting easier.
If you’ve noticed a Cooper’s hawk in Chicago or one of Scotland’s sparrowhawks in Edinburgh, you’re not alone. Habitat loss, historic pesticide use and other factors may have once threatened the raptor populations, but they’ve adapted quite well to urban life. That’s good news, says a research team from the University of Wisconsin at Madison, because it means we can learn to protect wildlife in the city.
“The more we know about which species and what landscape factors allow those species to colonize and persist in urban areas, the better we can manage wildlife in an ever-developing world,” says Jennifer McCabe, a university postdoctorate fellow who led the study published in Proceedings of the Royal Society B. We tend to discount cities as wildlife centers, but the woodland hawks at backyard feeders who fought back from decades of decline may offer helpful insights as societies move ahead into an uncertain future.
The Chicago study followed two types of hawks – the Cooper and the sharp-shinned – from the late 1990s until the present. Across two decades, hawks that once occupied just 26 percent of sites in the third-largest city in the United States had moved into nearly 67 percent. It’s largely because of the bird feeders.
“Millions of households in cities throughout the world feed wild birds and sustain their populations at elevated densities,” said McCabe and the research team. “This hyperabundance of prey, supported by supplementary feeding, provides an important and predictable food resource for avian predators.”
With support from bird enthusiasts who report what they see to the Cornell Lab of Ornithology’s Project FeederWatch, the scientists learned a bit about how the woodland hawks behave in the backyard too. Wildlife biologists call these hawks “perch and scan” hunters because they wait patiently on tree branches and then swiftly swoop down on their prey.
“Bird feeders are like buffets,” says Benjamin Zuckerberg, a University of Wisconsin–Madison professor of wildlife ecology and a senior author of the study. “It is an easy meal.”
With abundant food, the hawks move away from the urban periphery and grow tolerant of the people and traffic in dense urban environments. Many of the hawks are now city-bred in what have become their permanent homes.
Other studies have found similar patterns among goshawks in Hamburg, Germany, and sparrowhawks in Edinburgh, Scotland. Scientists studying the latter found that sparrowhawks in the city were thriving and had better breeding success than their country cousins.
“Gardens and parks hold large numbers of songbirds, which these raptors feed on, and the structure of urban landscapes in Edinburgh and other European cities, with parks and woodlands right next to private gardens, provides an ideal hunting environment for sparrowhawks,” said the authors of the 2017 paper, published in the journal Écoscience.
Yet if it’s good news for raptor populations, it’s less so for the songbirds. Try placing feeders beneath a porch roof or awning to shield them, and avoid scattering bird seed on the ground because it makes small birds more vulnerable. Shrubs and other landscaping also can give small birds a place to escape. Or, as the raptors themselves have done, bird enthusiasts may wish to adapt and accept the predators as part of the urban landscape too.