Question:
I had a House finch nesting in a hanging planter in my backyard last year and a Brown-headed cowbird laid an egg in their nest. If I see this happen again, should I remove the egg?
Response:
House finches are commonly parasitized by Brown-headed cowbirds to the tune of about one-quarter of all their nests. This means that the latter species, which does not make its own nest, lays its eggs in the nests of other species, 220 of them to be exact. It is not really a good thing for the host species if only because the main goal of all wildlife species is to pass their genes onto the next generation. If the Cowbird nestling does out-compete the host’s young to their detriment, then the Finch pair ends up raising some other species’ youngster and not their own nestlings containing their genes. As for you removing the Cowbird egg to help out the Finches, I can give you three reasons why you should not do so. First and foremost, it is totally illegal to tamper with the nest and eggs of any migratory bird species, including House finches and even Cowbird eggs. Second, the Cowbird’s parasitic behavior is a natural process and we really should not interfere with it. Brown-headed cowbirds, which are far too often vilified by the public but are in fact quite interesting birds, deserve to live too, right? Here is one more reason. One study suggests that if you remove the Cowbird egg, there is a chance that the House finches will desert their nest. But let me leave you with some good news. A study in southern Ontario in the mid-1900s found that while 85 percent of Cowbird eggs do hatch in House finch nests, the vast majority of the Cowbird nestlings do not fare well, mainly because the host parents’ diet is not that appropriate for them. So, the bottom line is that we should just let nature take its course and simply enjoy the drama and intrigue of it all.
David M. Bird, Ph.D., Emeritus Professor of Wildlife Biology, McGill University www.askprofessorbird.com
David M. Bird is Emeritus Professor of Wildlife Biology and the former Director of the Avian Science and Conservation Centre at McGill University. As a past-president of the Society of Canadian Ornithologists, a former board member with Birds Canada, a Fellow of both the American Ornithological Society and the International Ornithological Union, he has received several awards for his conservation and public education efforts. Dr. Bird is a regular columnist on birds for Bird Watcher’s Digest and Canadian Wildlife magazines and is the author of several books and over 200 peer-reviewed scientific publications. He is the consultant editor for multiple editions of DK Canada’s Birds of Canada, Birds of Eastern Canada, Birds of Western Canada, and Pocket Birds of Canada. To know more about him, visit www.askprofessorbird.com or email david.bird@mcgill.ca.
