This afternoon, I heard the querulous call of my first yellow-bellied sapsucker of the season. This migratory woodpecker breeds in mixed coniferous woodlands in the northern forests, then winters in the southern U. S. and in Mexico. Unlike their woodpecker cousins, sapsuckers prefer to feed on live trees. They take a delicate approach to drilling, making horizontal lines of holes from which they drink sap and eat sap-tippling insects. With the sapsucker’s arrival, Sewanee’s woodpecker count is up to seven species. The others are: pileated, hairy, downy, red-bellied, red-headed, and northern flicker. (The endangered red-cockaded woopecker used to breed in Savage Gulf, just north of here, but has been extirpated from Tennessee for more than thirty years.)
So far, this has been a good year for sightings of winter birds. Pine siskins have been quite abundant and I saw a pair of red-breasted nuthatches in early October. In some winters both these species are rare or absent. All this good birding for southerners results from hard times for the birds up north. When pine and hardwood seed crops are poor in Canada and the Northeast, birds are driven south by hunger.
According to Ron Pittaway of the Ontario Field Ornithologists, this will be a bad year for northern seed crops. His “bird forecast” focuses on Ontario, but what happens up north will be reflected in bird life across the country.
Humans add an interesting overlay to this natural year-to-year variation in food supply. As I note in The Forest Unseen, our love of birds results in the transport of millions of tons of sunflower seeds from the former prairies into bird feeders all over the country. This makes life easier for many birds, causing some of them to expand their winter ranges northward. Bird-hunting hawks therefore also linger in the northern woods. Our bribes have shifted the calculus of migration.
We know surprisingly little about how feeders affect the day-to-day behavior and ecology of birds. New technology, deployed (appropriately enough) at Sapsucker Woods where the Cornell Lab of Ornithology is located, is starting to shed some light into these questions. Least we humans feel left out, the same technology is being used to study our own “day-to-day behavior and ecology” and, like the birds, as long as the sunflower seeds keep coming, we’re happy to play along.