Swallows and other "aerial insectivores" are declining nationwide, which is why researchers around Alaska are ramping up efforts to monitor tree swallows using special nest boxes.
Each spring in Bristol Bay, there’s one migratory bird species that’s celebrated, not for the hunting opportunity, but for its appetite for mosquitos and white socks.
Tree swallows nest in small tree cavities or in nest boxes. This spring, U.S. Fish and Wildlife Service biologists in King Salmon have doubled the number of nest boxes available, in order to better study the tree swallow population in the area.
When the Fish and Wildlife Service put out a call this year for help with their tree swallow project, they got a huge response – about 40 people responded asking to have special nest boxes put up on their homes or buildings.
"Everybody loves the tree swallows because they eat a lot of insects," explains Melissa Cady, a wildlife biologist for the Alaska Peninsula/Becharof National Wildlife Refuge in King Salmon.
The reason for the monitoring project, says Cady, is that the whole "guild" of birds that eat insects on the wing, called "aerial insectivores," have been in decline across North America. For some species, that could be due to a loss of habitat, like forests or grasslands.
But researchers want to know more about this dramatic decline, and the swallow monitoring project is one piece of that puzzle.
"There’s a network of tree swallow monitoring sites across the state now, in Fairbanks, Juneau, here in King Salmon and a few other locations," says Cady. "And what we're doing is putting up nest boxes and we're monitoring the nests over time so we can find out the occupancy, the productivity of individual birds - that is to say, how many offspring they have - and survivorship over time."
They’re also looking at what happens to these cavity nesters throughout the course of the season. Cady says there’s been some evidence in the Lower 48 that tree swallows there are having their nesting season earlier than usual.
"The first hatch date has moved up by something like 9 days since the late 1950s when people started recording this," says Cady. "So we're looking to see if birds here are responding to changes in climate as well."
USFWS has been monitoring tree swallows in the King Salmon area since 1997, but Cady says this year’s new set of boxes represents a huge jump in the sample size of the project, from about 45 boxes to 82 boxes. Those include a few that were built and monitored with the help of students from the Naknek school.
And though Cady and her team are thrilled by the enthusiasm from the community, they say 82 boxes is about as many boxes as they can manage for now.
The study is partially funded by the nonprofit Alaska Songbird Institute.