The Baltimore orioles and yellow warblers are missing from the trees and bushes near the office of Emma Greig, a project leader for Project Feeder Watch at Cornell Lab of Ornithology in Ithica, New York.
“What I've noticed most in the past couple of weeks as I've walked into the office is actually a lack of [bird] songs,” Greig says. “It means that fall is here, or fall is on its way and winter is coming.”
There are some five billion song birds in North America, and over half of them don’t have a year-round home. Instead they drift north and south, migrating with the seasons. This migration that happens in the spring and fall is a great time for bird watching.
“During the migration time is that there is an influx of new species that pass through. There are species that have been here all summer that leave, and then there are some species that live in more northern locations such as tree sparrows and snow buntings that will show up, so there's a change in the species composition that'll come to your backyards,” Greig says.
Birds do more than migrate in the fall. Many non-migrating species also change their behavior. Blackbirds, for instance, are known to participate in ‘flash mob’ type behavior.
“They start going from being in territories where they're raising young and building nests and they begin congregating in really large flocks, which they'll stay in throughout the winter,” says Greig. “And, this becomes really conspicuous because huge, huge flocks of thousands of blackbirds often composed of multiple species, red-wing blackbirds, grackles, cowbirds will visit people's feeders and they'll do so all at once. And it can be quite overwhelming to have that many individuals coming to eat your cracked corn and black oil sunflower seed.”
Greig encourages people to watch for changes in bird populations in their backyards during migration. And she says feeding birds won’t discourage them from migrating.
“There are many internal and external cues that birds are using to tell them when to migrate and having a little snack is the last thing that's gonna keep them from doing it,” Greig says. “If anything, a little feeder, a little seed, a little nectar, will help them on their journey.”
When it comes to hummingbirds, which are known to fly all the way across the Gulf of Mexico in one giant shot of endurance, she recommends “Flowers, feeders, a little bath water. Hummingbirds will come and drink bathwater or you can put out a mister.”
Greig says bird migration has been affected by climate change in recent years.
“Biologists who are studying this have been observing this in some species, although not all, they're noticing an advance in arrival dates in spring. So, as winters are becoming more mild, the locations are becoming warmer. Birds are in some cases showing up to their breeding grounds earlier,” Greig says. “Whether or not that's actually good for them depends on a lot of other factors.”
But for bird lovers, the best thing Greig recommends is keeping an eye on what’s happening in your own backyard.
“It's a really complicated puzzle to solve and I think that the take home message for listeners is that this is a really important time to be watching the birds that are coming to your backyard and it's a great time to be participating in bird counting efforts such as the Christmas bird count, or E-bird or Project Feeder Watch. Because lots of things are happening now, because the climates are changing.”