Wednesday, September 16, 2009

feeding birds

People often ask me whether feeding birds is good or bad. Perhaps it’s both. I feed birds because I love to have them in my yard, not because I think I’m doing them a great favor. In the lowlands of the western part of the Pacific Northwest, perhaps the only time we really aid birds by feeding them is when snow covers the ground, making it difficult for some species to find food. That’s when I see species at my feeders that I didn’t even know were in the neighborhood. Varied Thrushes and Fox Sparrows are two good examples.

Normally, natural selection eliminates the least capable individuals from a population during hard times, and by our feeding them this winnowing may not take place. It may even boil down to helping individual birds to the detriment of the gene pool of their species. So when we make bird populations increasingly dependent on our handouts, we may be obliged to continue feeding them. Birds that normally winter in the tropics may take up residence at a feeder in the fall and not migrate south; they will probably be in trouble if the feeding is discontinued. Many birds (for example, Anna’s Hummingbird in the PNW) have probably expanded their winter range because of dependable bird feeding.


However, there is also a downside to bird feeding. Cats haunt the shrubbery and accipiter hawks visit from time to time; birds kill themselves against windows; and disease spreads readily at feeders. All of these sources of mortality are there without feeding, but the concentration of birds at feeders exacerbates them.
And then there is our subsidy of introduced species. I live next to a green belt in Seattle, with a nice variety of birds, but starlings often dominate the suet in summer and House Sparrows the seed feeders all year until a recent and surprising decline in both species in my neighborhood (lack of nest sites?). 


When Rock Pigeons visit, all too frequently, they easily displace native Band-tailed Pigeons. Millet feeders attract cowbirds, which parasitize native passerines, although cowbirds have also declined dramatically in Seattle. And don’t forget the gray squirrels and rats that compete with the birds (and eat their eggs). I don’t know any way to avoid this when feeding birds.


The feeding of waterfowl at parks is even worse, leading to the proliferation of semidomestic ducks and geese, as well as pigeons and sparrows. Diseases transmitted by these birds will of course infect wild populations. Birds of the native species are quite able to find their own food, but some of them become virtual beggars, a far cry from the traits for which we admire them!


It sounds as if I’m arguing against it, but in fact bird feeding at our homes is probably benign for most birds and furnishes much pleasure, as well as personal education, for us. There is also greater knowledge of the birds when their occurrence is recorded on Cornell University’s FeederWatch (http://www.birds.cornell.edu/pfw/) or  ebird (http://ebird.org/content/ebird/). In any case, the real favor I think we can do for birds is to fill our yards with plants that attract insects (just the opposite of the gardener’s strategy), bear edible fruit and bird-pollinated flowers, and/or furnish good nest sites. And lay off the pesticides.

Dennis Paulson

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