August 24, 2016
Highlights from a presentation by FeederWatch project leader, Emma Greig, at the North American Ornithological Conference 2016. She summarized research being conducted by her and by Cornell Lab Citizen Science director, David Bonter.
Food is a major determinant of the distribution, evolution, behavior and persistence of species, as has been shown by an abundance of supplemental feeding studies on small scales. But despite 50 million people in the US offering billions of pounds of seeds to birds every year, we know very little about the consequences of this hobby on native species in North America.
If supplemental feeding is ecologically detrimental, then we would expect to see long-term population declines in the species that consume the most supplemental food. According to the State of North America’s Birds 2016, one-third of all North American bird species need urgent conservation action. We looked at 30 years of FeederWatch data collected by thousands of project participants to select 135 species using feeders occasionally to regularly. Then we looked at the population trends for those species using 50 years of Christmas Bird Count data.
Overall, species that utilize bird feeders the most were doing better over time, rather than worse, and the few species showing declines include non-native species (House Sparrow, European Starling) or species suffering from novel diseases (House Finch). The species most in trouble, such as seabirds and shorebirds, don’t come to feeders and are declining because of other threats. Feeding birds may not help the hardest-hit species, but it may inspire people to support conservation.
We still have a lot to learn about the impacts of feeding birds, such as possible indirect effects on migratory species, or possible effects on generalist predators such as crows that may subsequently impact populations of non-feeder birds or small animals. Nonetheless, this work gives us some insights about how feeding birds impacts the species the use feeders the most.