I’d wager a significant percentage of birders and readers of this blog enjoy attracting birds to your yards, be it through a feeder or two or wildlife specific landscaping. It’s one of the great joys of having a spot of your own, and an opportunity to bring the birds to you rather than expend the effort the other way around. But bird friendly yards have a cost, not least of which in that they attract wildlife to places where they are more likely to come into contact with feral cats, cars, windows and other components of the developed world.
We are increasingly aware of the impact of skyscrapers and large buildings on migrating birds, thanks to a number of citizen science projects like Toronto’s Fatal Light Awareness Program. A study recently published in The Condor: Ornithological Applications sought to discover precisely how much impact smaller scale structures, particularly those seen as wildlife friendly, have on those birds. And the results suggests that it’s quite a lot.
A stunned Overbird recovers beneath a window. Photo: Andria Lavine via flickr
Working with Alberta homeowners who collectively contributed more than 34,000 days’ worth of collision data, Justine Kummer of the University of Alberta and her colleagues found that the presence of a bird feeder, whether a house was in an urban or rural area, and the height of the vegetation in the yard were the most important predictors of collisions. Of Alberta’s 421 bird species, 53 were represented in the data, mostly common urban species.
While the number of bird collisions per structure was fewer than what one would see in a skyscraper, the total number of birds affected are much higher because there are so many more residential dwellings across the continent. And while homeowners are unlikely to remove their feeders or cut down their trees and shrubbery, there are efforts that can be taken to help mitigate these deaths. The authors encourage the use of tapes, films, and other treatments that can help to prevent bird strikes. There are certainly advantages to encouraging wildlife friendly backyards in terms of outreach and aesthetics that are important in their own way.