DNR-led Study Tracks Rare Species from Georgia
By June, saltmarsh sparrows are gone from Georgia’s coast, flying from the southern rivers of grass where they winter to marshes from Virginia to Maine where they nest.
Although gone, however, they are not forgotten: They are followed.
Thanks to a tracking project by the Georgia Department of Natural Resources and U.S. Fish and Wildlife Service, this spring’s migration could help pinpoint where saltmarsh sparrows from Georgia breed. Such connections are considered vital to conserving a species that otherwise could go extinct in 50 years.
The problem is that the tidal marshlands that give these birds life and name are being squeezed by coastal development and sea-level rise, said DNR wildlife biologist Tim Keyes. “Their nest numbers are dropping and habitat is being lost. Marsh migration is not occurring at a rate to replace habitat loss.”
The estimated number of saltmarsh sparrows has shrunk from 250,000 to 53,000 since the start of the century. Their secretive nature – living in marsh grasses, seldom singing – helped mask the decline.
Yet the advent of mini-transmitters light enough for animals that weigh only about a half-ounce has opened a window into the lives of these and other species. In March, Keyes and Adam Smith of the U.S. Fish and Wildlife Service led volunteers in netting and attaching “nano-tags” to 25 saltmarsh sparrows near the Jekyll Island causeway (video) and on a marsh island off Little Cumberland Island (Flickr photo album).
As part of work funded by a National Fish and Wildlife Foundation grant, antennas have been erected at Brunswick and on Ossabaw Island. A third is planned on St. Simons Island. Each registers signals from tagged birds that pass within about 15 miles, Georgia’s entry into a hemispheric wildlife tracking system called Motus.
As of June 1, Georgia towers had picked up 11 of the saltmarsh sparrows tagged here. As they fly farther north, a Motus network more developed in the upper Eastern Seaboard will track them. Project leaders expect that data to begin trickling in soon. The transmitter batteries last 70-80 days.
Smith, a quantitative ecologist with the Fish and Wildlife Service, explained that recent research using Motus to study the spring migration of thrushes demonstrates the important role that a single stopover site can have on the speed and likely the success of migration.
“This effect may be even more prominent with a habitat specialist like the saltmarsh sparrow,” he said. “Thus, knowing where these birds are stopping to rest and refuel during migration, and how quickly they move after those stops, is crucial information to managers as the sparrows’ habitat continues to shrink.”
According to Keyes, who works with DNR’s Nongame Conservation Section, researchers studying migration previously had to rely on recapturing banded birds at different sites. It was a long-shot process: Of 184 saltmarsh sparrows banded in Georgia, “we had a grand total of one recapture,” Keyes said.
“This will be a much more efficient way to see where individuals that winter here are actually going.”
Saltmarsh sparrows are a high-priority species in Georgia’s State Wildlife Action Plan, a comprehensive strategy for conserving native wildlife and plant species statewide before they become more rare and more costly to restore.
- Saltmarsh sparrows nest in marsh grass near the high-tide mark, timing egg-laying to hopefully allow young to fledge before peak tides flood a nest. And while extreme tides destroy many nests, females will return to incubate eggs in flooded nests after tides recede, as shown here.
- Georgia’s Motus towers are picking up birds tagged in other projects, such as Kirtland’s warbler, black-crowned heron, piping plover and Swainson’s warbler (the latter included four birds tagged in Jamaica in April and picked up in Georgia in May). Motus is Latin for “movement.”
- Motus tracking (www.motus.org) of tagged saltmarsh sparrows migrating south in 2015 is illustrated at www.motus.org/data/demo/saltmarshSparrows2015.html.
- The netting along Jekyll causeway and U.S. 17 in March did land a saltmarsh sparrow PIT-tagged in Maine in 2015, where it nested. Project leaders hope to trace her return north by nano-tag.