For birds, migration is hard. Really hard. Many migratory species travel thousands of miles through all weather conditions with limited food resources. While many mysteries still remain around bird migration, scientists are learning more and more about the whys and hows of this incredible phenomenon. And it has a group of scientists in the Northeast asking: can we make migration a little easier for some songbirds by enhancing their favored habitats?
In 2015, a collaborative project began between the U.S. Fish and Wildlife Service, the University of Massachusetts, and the U.S. Forest Service’s Northern Research Station. By collecting data on bird health and by tracking movements of migrating songbirds in the Connecticut River Valley, the team hopes to determine the best habitat types for certain migratory birds that stop over in the area.
To gather this information, the team has been capturing woodland birds during spring and fall migrations using mist nets. Once captured, birds are banded and several measurements are taken including wing and beak size. Blood is drawn from some target species and brought back to a lab for analysis. The research team is getting a picture of the birds’ overall health by determining body composition (fat, lean mass, and water content), and instantaneous refueling rates which help determine if birds are gaining or losing mass during a stopover.
Additionally, select birds are fitted with NanoTag transmitters which allow biologists to track the birds’ movements. NanoTags are tiny tags that emit a signal that can be tracked with telemetry equipment. Biologists can identify individual birds and their locations for months using the devices that are attached to the birds with a tiny elastic harness. Among the species targeted in this study are Swainson’s thrushes, northern waterthrushes, yellow-rumped warblers, Lincoln’s sparrows, and white-throated sparrows. Data collection for this project wrapped up this spring; and over the past four years, biologists were able to band nearly 3,000 birds and fit over 200 target birds with NanoTag transmitters.
This study has been taking place within the Silvio O. Conte National Wildlife Refuge. The Refuge encompasses an impressive 36,000 acres of the Connecticut River watershed in the states of New Hampshire, Vermont, Massachusetts, and Connecticut. The team has focused its capture and banding efforts on old-field sites within the Conte Refuge for this study, including the Fort River Trail area in Hadley, MA and the Orchard Hill section of the University of Massachusetts in Amherst, MA. Each site is less than 1/3 of a mile from the Connecticut River.
U.S. Fish and Wildlife Service wildlife biologist, Troy Wilson, says, “We are interested in how physiological condition affects performance during the life stage of migration. Condition metrics – fat, lean mass, water – are used as indicators of the heath of birds, as well as a means to determine the quality of the habitats they occupy as they refuel from one location to the next.” The end goal is to determine how the Connecticut River Valley and the Silvio O. Conte National Fish and Wildlife Refuge can be a better host for migrating birds. The team hopes to be able to make recommendations for habitat management, specifically where forested areas should be converted to early successional habitat through forest management, and where old fields and shrublands might be managed for specific plant species and habitat structure that provide the highest benefits to birds during migration.