6 Common Bird Migration Questions, Answered by Our Expert

[soundscape of birds calling] [text on screen: Ask an Expert: Top Bird Migration Questions. Dr. Kevin J. McGowan, Bird Academy Senior Course Designer. Highlights from a webinar recorded in Sept 2023. Image of two Sandhill Cranes in a marsh. Logo: Cornell Lab] [text on screen: Why do birds migrate?]

People should know that not all birds migrate.

Some birds just stay in the same place all year long. So if we think about the birds up in the boreal forest, the chickadees stay there all year round. They can find, believe it or not, insect eggs and little things like that in the bark, that they can find enough food to keep them, keep them going during the winter. But a lot of the other birds feed on flying insects or moving insects,  and there aren’t too many of those, up in Canada in the wintertime, so they have to go somewhere else to find food. Migration is almost always about finding food. It’s not to get out of the cold because birds can survive cold. But there are certain inhospitable places that they need to leave. But it’s almost always about food.

[text on screen: What prompts birds to start migrating?]

Well, the thing that starts bird migration usually is a change in daylight and what that does is that starts this sort of, the, the proximate mechanism that gets the birds brains changing, different hormones being produced, and the birds can sense even very small changes in daylight length. There’s this cool term that’s in German called Zugunruhe and that means migratory restlessness.

[text on screen: Zugunruhe. Migratory Restlessness]

And so we can you can watch this. And it’s been well studied in birds that if you keep them in captivity, as the light changes, as the days get smaller or longer, they start to get antsy and they just kind of move around in their cages and they just want to go somewhere. And it’s just this need to, to go further, to go further, go south, go south, go down, you know.

[text on screen: How variable is migration timing?]

In fact it’s actually fairly rigorous in some species. It’s very, very predictable. Like when Red-winged Blackbirds turn up in central New York, is is always within a two week period. And so some of these things are very precise. However, migration on, you know, for an individual bird depends on the, circumstances that that bird is in. And that includes changes in weather and, and local conditions and stuff like that. So there’s always that sort of fine tuning. So it’s never precisely the same.

[text on screen: Do adult and juvenile birds migrate together?]

Yeah, that’s an interesting thing about migration is we tend to think, oh well, yeah, they just go—But they don’t There are different… different… the sexes do different things. And the juveniles do different things. And typically what you see going first are the males, the breeding males of a lot of different birds leave the breeding grounds before the females or the juveniles do. And then as a… again, as a general rule of thumb the adults leave first and then the juveniles leave later. And it may be they just need a longer time to fatten up, to migrate. But that’s very a very predictable pattern that we see

[text on screen: What’s the best time of day to migrate?] [image: map of continental United States in purple, orange, and yellow against a black background, colors indicate predicted strength of bird migration. Text on screen: Migration intensity scale: white = High; yellow to orange = Medium; purple = Low; dark = None. 378 million birds predicted. Logo: BirdCast]

Different birds do migrate at different times of the day. And to,  a lot of people are surprised to know that the the bulk of migration happens at night, that most birds fly at night. And there’s several reasons for this. One is that they, you know, there are fewer predators being able to catch you at night. You can’t really forage that much, so you might as well fly.

[Image: graphic of a flying Yellow Warbler against a globe depicting lines of magnetic force]

When there’s not enough light to see very well, birds can actually turn on a different sense and see the magnetic fields of the earth. And so they can tell north and south, because they can see the magnetic fields. I read that news and it’s like, oh, that’s why they fly at night is because then they can see. And that does seem to be the consensus is that, a lot of the nighttime flying, is because that allows them to use their magnetic sense to detect north and south.

[text on screen: How can people help migrating birds?]

Well, hummingbird feeders, the hummingbirds really like hummingbird feeders, and you won’t make them stop migrating, and stick with it and stick with your feeder till it gets cold. They’re not going to do that. But they will use it as a source of, cheap energy that they can put on and, and, help them along their way. Suet for some of the other birds is good. The other thing to do to help birds along during this is turn off your lights at night. That’s a big one. And of course, this really plays out in the cities. And, and there are the programs that people have, a number of organizations are working with, including the Cornell Lab of Ornithology, that are trying to encourage big cities to cut down on their light usage during peak migration time because birds get confused. And so turn off your lights at night, plant native plants, put up a hummingbird feeder. That doesn’t do it all. But there are a couple of tangible things that people can do.

[text on screen: Media Credits: Oregon soundscape by Todd Sanders / Macaulay Library; Sandhill Cranes by Dylan S. / Macaulay Library; Blaack-capped Chickadee by Nick Saunders / Macaulay Library; Tree Swallow by Blair Dudeck / Macaulay Library; Whimbrels by Matt Aeberhard / Macaulay Library; Red-winged Blackbirds by Ron Beurkert / Macaulay Library; American Avocets by Matt Zuro / Macaulay Library; BirdCast Migration Forecast 6 Sept 2024 / Cornell Lab and Colorado State University; Geomagnetic illustration by Jillian Ditner / Cornell Lab; Calliope Hummingbird by Joshua Glant / Macaulay Library; Nighttime view from space by NASA / JPL.] [soundscape of bird calls ends]

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