Laura Erickson's For the Birds

Capitalizing on Death

This week I got a phone call from a listener who’d just had a surprise. A warbler crashed into his window, and the sound made him look out to see it trembling on the ground. Before he could even react in swooped a Blue Jay and picked up the still-alive little bird. Blue Jays eat far more plant matter than animal, and except for raiding the nests of other birds in spring to provide needed protein to their babies, couldn’t really be called predators. So what was going on?

Although the diet of Blue Jays is 88% vegetal, they are opportunistic omnivores. The 12% of their diet that is animal comes mainly from insects, but they also scavenge on dead animals. They aren’t quick enough, or usually temperamentally disposed, to kill healthy birds, but they do pick up dead ones, and the fresher the better. Since so many birds that collide into windows do die, some jays have figured out that the sound of a window smack means an easy meal. And if the victim is alive but stunned, it’s not going to be able to put up much resistance—after all, a third of an ounce warbler weighs only one ninth of what a three-ounce Blue Jay weighs. If the jay waits politely, vulture-like, until the bird dies, it may well lose the meal to a crow.

Apparently many animals have learned to associate certain sounds or sights with fresh and easy meals. I’ve heard from several people this fall who’ve noticed that crows fly in to look over the scene when a bird smacks their windows. And with the pretty-much unprecedented number of warblers grounded during this cold-snap, crows are having a field day on streets and highways—I watched one swoop down and pluck up a still alive warbler on a busy highway in Duluth, watched another swoop in between closely-packed cars at a stop light to pick up a dead one, and have seen scores of crows flying with dead warblers in their beaks. When I was driving home this week, I saw three dead warblers on the avenue by my house. Ten minutes later I drove away on that same stretch, and all three bodies were gone.

Of course birds aren’t the only animals savvy enough to figure out how to get an easy meal. A friend of mine once heard a buzz and snap, and looked out the window to see a flash of light and an electrocuted squirrel dropping dead from atop a power pole. Within seconds, a fox rushed in and stood over the still-sizzling squirrel for a few minutes, apparently waiting for it to cool, and then picked it up and ran off into the woods with it. Squirrels don’t get electrocuted every day in my neighborhood, but the fox had apparently learned to associate that sound with a freshly-cooked meal.

Interesting as it is to think about the ways scavengers capitalize on dead animals, it’s sad, too, especially this year when so very many warblers are dying right in our midst. People have brought me several yellow-rumps that had been stunned at their windows. The poor little birds have all been quickly released, but they’ve all been grossly underweight, their keel bones jutting out because their breast muscles have shrunk with hunger. These insect-eaters are finding slim pickins after all the cold weather, and there really isn’t much we can do to help them except to slow down for another week or so until they’ve passed through the area.