Wayne Grady is the author of numerous books of science and nature, including The Great Lakes: The Natural History of a Changing Region and Tree: A Life Story, co-authored with David Suzuki.
A few summers ago, when a merlin flew over our backyard bird feeder in Kingston – not even a merlin, but the shadow of a merlin – every songbird at the feeder instantly disappeared or froze. The chickadees vanished into the maples, a pair of nuthatches seemed to morph into the bark of a nearby pine, even a hairy woodpecker on a dead elm branch went perfectly still, until the merlin passed and a blue jay sounded the all-clear.
Fascinated though I was by the sudden tableau – it was like being in one of the Royal Ontario Museum’s dioramas – I wondered if by providing a steady food source for songbirds, I may also have been providing a steady food source for birds that prey on songbirds.
Apparently, I was. All About Birds, a website maintained by Cornell University, warns that birds of prey such as merlins and kestrels are attracted to bird feeders, but that if I took the feeder down for a few days, the hawks would lose interest and the songbirds would return. On the other hand, according to a recent study to be published in ScienceDirect this September, while bird feeders tend to become hyperactive centres for both songbirds and predators, “this association was not significant.” In other words, there is no percentage increase in bird predation at feeder sites. Hawks eat the same number of birds a day, whether the birds are at feeders or foraging in the wild. And most of the predation that occurred at the study sites wasn’t by hawks or falcons, which are natural predators, but by feral cats, which are a byproduct of us: Cats made up 80 per cent of the predators attracted to the feeders in the study and, like habitat loss, office-tower windows and heat domes, cats are human-created disasters that have contributed to the loss of about three billion North American songbirds since 1970.
I left our feeder up and continued feeding birds.
I still worried, though, that by feeding birds, I might make them dependent on feeders – that I was, in a way, domesticating them. Indeed, some species have changed their migration habits, preferring to hang around feeding sites in the north rather than migrate to their winter feeding grounds in the tropics. American robins, for example, a migratory species, are now found overwintering in every Canadian province, and many Canada geese now spend their winters on the beaches of Lake Ontario.
But in neither case is it because we feed them, at least not directly. Geese stay because their principal food sources – grass, sedges and aquatic plants – are less likely to be buried under snow. Robins hang around because worms and grubs are available year-round. Lakes no longer freeze over. These birds no longer need to migrate to find food. But at my feeder, we don’t feed robins or geese. Except for the occasional grackle, winter visitors to our feeders are songbirds: house sparrows, house finches, jays, cardinals, juncos and chickadees.
The alternative to overwintering is returning to northern breeding grounds earlier than usual, and that’s not necessarily a good thing. If the weather suddenly turns cold, plants and insects can go back into diapause just as the birds’ eggs hatch, making parents’ foraging more difficult. Fewer hatchlings survive, in which case, backyard feeders take on more importance than ever. Hummingbirds in particular are having a hard time lately, as climate change is affecting pollinating insects and insect-pollinated plants – insects constitute up to 80 per cent of hummingbirds’ diet. When the weather is very hot, we increase the proportion of sugar to water in our hummingbird feeders from one-to-four to one-to-three, but we’ve still seen fewer hummers than in previous years, as hummingbird populations are in decline throughout North and Central America.
My wife and I spend our winters in Mexico, so I wondered if birds suffer when we stop feeding them in the fall. I was relieved to read several studies that found no reduction in songbird populations when feeders that had been maintained for many years were taken down. The birds found other sources of food. Researchers from Oregon State University trimmed the flight feathers of a few dozen chickadees to make flying more energy-consumptive; they wanted to see if the extra calories the birds needed to fly caused them to become more dependent on feeders. It didn’t: Initially, at least, the clipped birds actually spent less time at feeders. “Feather-clipped chickadees reducing their use of feeders,” wrote the researchers, “suggests that food in the environment – like seeds, berries and small invertebrates – were sufficiently available to compensate for the increased flight costs.” It was easier for the birds to forage near their nests than to fly to the feeders. After a week or two, the clipped birds began returning to the feeders, but only because they had stored enough energy in the wild to do so.
This year we had a new worry, as spring-migrating birds brought avian flu (H5N1) to Canada. In Kingston, geese began dying of avian flu in February. The disease spread to other species, mostly to scavenger species that fed on the carcasses of dead Canada geese: bald eagles, turkey vultures, ravens and crows. While avian flu is a serious threat – especially when it spreads to commercial flocks of domestic fowl – scavengers rarely visit bird feeders. We’ve had wild turkeys demolish our feeders, but never turkey vultures.
Human activity worldwide has not benefited wild animals, and bird populations are plummeting everywhere. Wind turbines decimate hawks; as many as 42 million birds a year smash into windows in Canada alone; the American Bird Conservancy estimates that domestic cats kill up to 2.5 billion birds each year; the oil and gas industry has destroyed most of the remaining greater sage-grouse habitat in Alberta. We’ve drained wetlands and cut down swaths of the boreal forest, where most of our birds reproduce.
We have not been kind to the birds. Feeding the survivors at our backyard feeders seems such small compensation. We don’t need to find reasons for not doing it.
