Migrating birds are sneaky. Most travel thousands of miles without being seen, then suddenly pop up in your backyard. That’s been happening a lot this week.
Most migrants travel at night. The air is refreshingly cool, the wind is more favorable, the stars aid navigation and darkness hides the birds from predators. Their movements are mostly invisible, but not entirely. Birds are smart enough to avoid flying into a headwind. They will wait until conditions are favorable. Then many birds will depart all at once — so many that huge nocturnal flocks show up on radar.
At daybreak, these flocks settle down somewhere. Usually, you can tell when a group of birds is traveling together. Last Saturday, I had nine dark-eyed juncos running around my lawn, where none had been the day before. They came in overnight, stayed a day, then left again.
You can also tell when local breeders have just arrived. Last week, I was in Lubec. The beaches were covered in song sparrows, foraging in the seaweed left by the falling tide. Although most had reached their final destination, they had not dispersed yet.
When birds reach their nesting areas, they’ll often spend a day or two foraging together, refueling after the long flight. Then, they spread out, avoiding each other, selecting and defending territories and competing for mates. My first eastern phoebe appeared in the yard Tuesday morning, already dispersed from his competitors. You might notice these migratory patterns as April progresses.
It will happen again when the warblers return. Pine, palm and yellow-rumped warblers are all due in about 10 days. The palms and yellow-rumps are especially prone to falling out together upon arrival. Pines are particularly likely to start singing on territory the moment they arrive. About that same time, expect yellow-bellied sapsuckers to make an obvious and noisy landfall. One day, you’ll hear none. The next day, these woodpeckers are drumming everywhere you go.
You’re never too old to learn. I was astonished by another invisible surprise last week. Picture this: I was near Sunkhaze Meadows National Wildlife Refuge in Milford, trying my luck with nighttime owls. My luck, as usual, was bad. But as I listened for owls, I instead heard an “owl-let.” That’s the call of a long-tailed duck. It was flying overhead in the darkness.
What?! Long-tailed ducks? At night? Over the forest?
Long-tailed ducks breed across northern Canada. Many spend their winters along Maine’s coast. Until that moment, I did not know they migrate at night. I don’t know how that information has eluded me all these years.
The mystery deepens. Where was that long-tailed duck (or ducks) going in the dead of night? It was late March. Most of the water farther north is still frozen. Its breeding grounds will be frozen for another month or more. Long-tailed ducks don’t typically leave the Maine coast until they’ve molted into their summer plumage, and molting for most birds hasn’t started yet.
It seems I have more to learn. Regardless, add ducks to the list of birds that migrate at night.
Geese may fly by day or night. Evidence indicates that they use landmarks for navigation during the day, but also stars to show the way at night. Geese generally live long enough that at least some members of the “V” formation know the route by heart.
Raptors migrate by day, riding a cushion of warm air as the morning heats up. Swallows, swifts and other insectivores migrate by day, so they can feed on the wing. Hummingbirds are daylight migrants. Birds that hopscotch over short distances, such as finches and waxwings, wander by day.
Fall migration is leisurely. Southbound migrants can take their time, in no hurry to get to their destinations. Spring migration is intense. It’s a balancing act for many. Northbound migrants want to beat their competitors to the best nesting spots, but not arrive so early that they freeze or starve.
You can watch this drama unfold over the next six weeks. You can even increase your odds of noticing by watching the weather. Clouds and winds from the north discourage migration. When the forecast calls for evening winds from the south or calm winds, the likelihood of a big migration night increases. A sufficiently clear sky aids navigation, also favoring a big night.
On the morning after a good migration night, I step onto my porch, coffee mug in hand, and listen to the cacophony of newly arrived birds. What a way to start the day.