Avian geolocator sensors are no bigger than a penny.
With populations of long-distance migratory songbirds in decline, Canadian researchers have launched two new studies that track migration schedules and routes of individual birds through the use of tiny geolocators.
Scientists have long tried various ways to attach sensors to birds. Neck and wing loop harnesses pose a number of problems, not the least of which is how the transmitters change bird behavior. Gluing techniques are more successful, but involve removing feathers and gluing patches to the birds’ backs, which is stressful for the animals. For these studies, geolocators were attached in a new manner, using leg-loop harnesses made of Teflon ribbon that allowed the sensor to rest on the birds’ backs. Extremely light at just 4% of the birds’ own weight, the geolocator and harness did not appear to affect the bird behavior or balance in flight.
Researchers from Toronto’s York University studied information retrieved between 2008-2011 at a breeding site in Pennsylvania and wintering sites in Costa Rica and Belize.
York researchers learned that spring migratory schedules are fairly fixed, based on the breeding habits of the birds, while autumnal migration schedules are less exact. The reasons for the very specific migration schedule in the spring may have to do with what happens when birds arrive at the breeding area too early (temperatures are too cold) or too late (less opportunity to find an acceptable mate).
The results of the York study appear to support the theory that one factor affecting population declines may have to do with migration schedules that haven’t adjusted as the overall climate has changed.
The data retrieved by the team at the University of British Columbia was collected in at locations in Vancouver and Kamloops, B.C.
In addition to tracking the birds’ migratory routes and interspecies breeding patterns, the UBC study plotted the birds’ stops along the way. This information may help conservationists preserve habitat along those routes; loss of habitat during migration is another key factor in the decline of long-distance migratory bird populations.
According to a media release from the university, the birds’ migratory behavior might also affect how the animals themselves evolve. Of interest are the varying routes different sets of animals took.
“Our teams of thrushes took dramatically different routes to get to their wintering grounds, either south along the west coast to Central America, or southeast to Alabama and across the Gulf of Mexico to Columbia,” said researcher Kira Delmore. “Birds of a feather do not necessarily flock together.”
Repeat migration routes of individuals tracked by Toronto researchers.