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Swamp sparrows like this one are nesting near Tappahannock. |
By RUSTY DENNEN
Bryan Watts and fellow scientists with the Center for Conservation Biology at the College of William & Mary have been doing some detective work in marshes along the Rappahannock River.
Last summer, a Northern Virginia bird-watcher reported seeing 14 rare coastal-plain swamp sparrows on the river near Tappahannock, so they decided to investigate.
What they found was surprising. Several of the small gray-and-rust-colored birds, a sparrow subspecies, were not only living there, but nesting and singing.
The bird was first described from a specimen taken along the Nanticoke River on Maryland's Eastern Shore in 1947, Watts said. Until now, the sparrows have been concentrated in salt marshes in New Jersey, Delaware and Maryland.
"Other than a small number of observations in the Dyke Marsh area on the Potomac River [below Washington], there are no modern breeding records for Virginia," Watts said.
What's also significant, he said, "is that over the past century or so there's been a contraction in their range." The birds are not listed as endangered or threatened, but only several thousand pairs are thought to exist.
So how did the sparrows wind up in Tappahannock? One possibility: "It could be that they've been on the Rappahannock all along," Watts said.
He and his colleagues examined Mulberry Point Marsh this spring, and found two other sites along the river harboring the birds. Watts said it will take more visits and study to determine just how many are there and how many are nesting.
"This is in kind of an early stage of documentation," he said.
Much about the secretive bird's lifestyle has been a mystery. For example, the sparrows would leave their home range in the winter, but until recently no one knew where they went.
Russell Greenberg, director of the Migratory Bird Center at the Smithsonian Institution's National Zoological Park, has been studying swamp sparrows for more than 20 years. He traced some wintering birds to spots along the North Carolina coast. The finding was featured in latest issue of Inside Smithsonian Research.
The Virginia Department of Conservation and Recreation's Division of Natural Heritage lists the swamp sparrow as "extremely rare and critically imperiled with five or fewer occurrences, or very few remaining individuals in Virginia."
According to the Migratory Bird Center, swamp sparrows don't live in swamps (forested wetlands), but in marshes. Their feathers are typically gray to black, the better to hide them from predators on a background of gray tidal mud.
Males have a bright red or rust-colored crown, and they often perch atop dead branches to sing and stake out territories. Females lay a clutch of three to five brown mottled eggs.
Watts and his crew map areas on foot and also do aerial surveys, and find singing birds to pinpoint their locations. "We might do that multiple times over the course of a season to know where their territories are," Watts said.
He suspects that there may be other small groups of birds elsewhere along the Rappahannock and Potomac rivers.
"There are some indications that there may be some up near Washington on the Virginia side" of the Potomac, he said. Watts said marsh areas suitable for the birds occur on the Potomac between Caledon Natural Area and Washington, and between Tappahannock and Port Royal on the Rappahannock.
Discoveries like this happen occasionally. For example, white ibis were first observed breeding in Virginia in 1979 and pelicans in 1987. "The most recent was the Mississippi kite, found breeding on the Potomac about five years ago," Watts said.
Unlike the swamp sparrow, those birds are expanding their ranges.
Watts said the Center for Conservation Biology would like to hear from bird-watchers about any field observations of the sparrow through this month.
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