Stretching their wings: Migratory birds start fledging
July in Aspen is peak tourist season. As part of a monthly series on Roaring Fork wildlife, Elizabeth Stewart-Severy checked in on some visitors from the south who are in the middle of some critical work this summer. It’s time for migratory birds to stretch their wings.
Jim Kravitz walks the grounds of the Aspen Center for Environmental Studies (ACES) with open ears, listening carefully for bird calls.
“If they've come here from somewhere else, they’ve come here to nest, and they should have young by now,” said Kravitz, director of naturalists programs for ACES.
He spots a small bird perched in a cottonwood.
“A fledgling bird is usually sitting, it looks pretty cute, a little bit fluffy. It’s got a short tail,” he said. “And they’re pretty helpless, but they’re out of the nest and they’re out of the nest for good.”
As these birds learn to fly, they often spend some time on the ground. This is prime time for learning the hard work of survival.
“Typically the parents are bringing it food; they’re teaching it where to find food. They’re teaching it how to get away from danger, get away from predators, where to hide,” Kravitz said. “They’re learning to be a bird. It’s basically those awkward teenage years that they’re going through.”
Like some human teenagers, a good place to hide and take refuge can be key.
“A lot of us in our yards, we cut down the brambles in the bottom of our trees, but that’s where the fledgling birds love to hide. Underneath the tight branches of a spruce tree, underneath there, that’s where they can be safe,” Kravitz said. “A lot of times when we manicure our yards, we get rid of that space, so that’s why they seem so helpless. Nowhere to go, nowhere to hide.”
Nesting is a vulnerable time for birds, and fledglings have to learn to avoid all kinds of predators, including other birds (like magpies), racoons and house pets.
Then it’s about gaining strength through the summer for the flight back south.
“Well the birds first of all have to gain enough fitness so that they can put on the muscles and the feathers so they can make the journey, because it’s a long journey,” Kravitz said.
Most of Aspen’s summer birds are insect-eaters — even hummingbirds — and food source is what drives the timing of their migration.
“So as long as they can find insects around here, they’ll stay here,” Kravitz said. “It’s not that it’s too cold.”
For some species, the trip home starts in mid to late August and for others, it’ll happen later into the fall. But just like anyone else with a favorite family vacation spot, there’s a chance those same birds might be back again next year.
“They have a lot of affinity to a nesting site, and will come back year after year, and the young of those will come back in the same area as well, often,” he said.
The classic Aspen repeat visitors — only next year, they’ll find a nest of their own.