With the arrival of summer, you will begin to catch glimpses of a small but speedy bird in flight, looping through the sky, searching for insects to eat. Its underside is white, and it sports a dark iridescent back that flashes varying hues of blue as the sunlight passes through its feathers. The tree swallows are back!
The tree swallow is one of several swallow species that come to Alaska to breed. This small songbird, weighing around 20 grams, arrives from regions as far south as Cuba, Costa Rica, Panama and the Yucatan Peninsula. Some tree swallows cross the Gulf of Mexico in one to three days of non-stop flight.
Here in Alaska, tree swallows are found throughout the southeast up through the Brooks Range and from the Yukon-Kuskokwim Delta to Canada. Their preferred habitat is open country near marshes, bogs and meadows, with plenty of flying insects to eat.
The Alaska Swallow Monitoring Network, a program of the Alaska Songbird Institute, is a collaboration formed in 2016 between researchers and Alaskan communities to monitor how climate change may be impacting the phenology and breeding habits of tree swallows. With monitoring sites that ranged across the state, including as far north as Anaktuvuk Pass, this research network allowed scientists, schools and communities to work together to study tree swallows at the northernmost extent of their range.
Tree swallows are aerial insectivores (birds that forage on insects while in flight). They, and other aerial insectivores, are facing steep declines. Since 1970, the North American avifauna has experienced an estimated net loss of 3 billion birds, approximately 29% of total avian abundance. Within that same period, the abundance of aerial insectivores declined by 32%, a decline equal to or greater than declines in all other groups of North American birds. By monitoring their breeding success and arrival and departure timing from their breeding grounds, scientists hope to gain insight into how tree swallows adapt to our changing climate.
If you live near a wetland or bog, you can help tree swallows by putting up nest boxes in your yard. Check the Cornell Lab of Ornithology NestWatch website for the proper dimensions for nest boxes for tree swallows.
You can also participate in Cornell's Nestwatch program. Participants track data such as when nesting occurs, the number of eggs laid, how many eggs hatch, and how many hatchlings survive.
Rachel Gingras is the Bird Treatment and Learning Center Administrative Assistant.
