Monday, January 19, 2009

Project to Trap, Track Godwits Means Long Day at the Beach

Cannons firing, people running, adrenaline pumping: no, it is not war; it’s banding birds – marbled godwits, to be precise.

The marbled godwit is a large migratory shorebird that nests in the grasslands of the Plains states and central Canada, as well as in Alaska and, in small numbers, eastern Canada. Godwits winter on the West, Gulf and East coast, including in Georgia. The birds will stay here until late April or early May, with a few juveniles remaining throughout the summer.

The marbled godwit is in decline, at least in part due to habitat loss, and listed by the U.S. Shorebird Conservation Plan as a high-priority species. Understanding the connections between winter habitats, nesting areas and migration stops for the various populations is vital to managing habitat for the species. The connections are also the focus of a U.S. Fish and Wildlife Service project encompassing North America.

On this chilly December morning, a group headed by Brad Winn, coastal nongame program manager for the Georgia Wildlife Resources Division, has spent most of the last several hours setting a trap to capture and satellite-track these cinnamon-colored birds with the upturned bills.

As part of the continent-wide project, small transmitters attached to the godwits will help biologists determine where the birds migrate and nest, what their movements are throughout winter, and other general location data. The marbled godwit is listed as a high-priority species in the State Wildlife Action Plan, a comprehensive strategy guiding Wildlife Resources and Georgia Department of Natural Resources efforts to conserve biological diversity.

The site is carefully chosen based on tide levels and bird sightings from the previous day. A trench is dug in the sand and the net laid. Two 4-by-6-inch blocks of wood with round metal pipes attached serve as cannons. They are filled with gunpowder and half buried in the sand after being attached to each side of the net with rebar. A wire attached to the fuses winds across the long stretch of beach to where the researchers are hiding … and waiting.

When it comes to catching birds, timing is everything.

After the trap is set, everyone sits back and waits. A variety of birds have begun to congregate in the target area, including American oystercatchers, long-billed curlews and, of course, marbled godwits. The hope is that as the tide comes in, the birds will move into the “net zone.”

Concentration and constant communication are crucial. Farther down the beach, Winn watches with a scope and radios. Chris Depkin, a wildlife biologist, is hiding in a different spot and holding the fuse.

“Not yet, just a little more,” says Winn, quietly urging the birds to move.

The window for capturing the birds is narrow. As the tide rises, they slowly move onto the sand bar and into the capture area. If the birds are not captured before the tide begins to recede, the chance will be lost, at least for today.

Sometimes they need a little help. Winn makes a call and two young men with a kayak soon come walking down the beach. Both have done this before and need little direction. Ben Morrison, a naturalist for Little St. Simons Island, pushes off and cautiously paddles towards the birds. The situation looks good, but anything can still go wrong.

If the birds become too wary, they will flush. If the kayak is too slow, the tide will come in and the birds will leave. Either outcome means everyone packs up and goes home for the day.

The kayak does its job. The birds scuttle almost imperceptibly to the right. Perfect.

What happens next seems like orchestrated chaos. Winn completes the countdown, the cannons are fired and then everyone is running toward the birds struggling in the net. Looks like a good catch.

Researchers work quickly to secure the trapped birds. Each is carefully removed and placed in plastic bins for carrying to the staging area where they will be measured, weighed, banded and examined. A few lucky birds will also receive the satellite transmitters.

When all have been sorted by species, the birds are secured under a large tarp, which shields them from the sun and helps them stay calm. Now the real work begins.

The team forms an assembly line of sorts to work faster. Winn and Depkin are in charge along with Scott Coleman, ecological manager from Little St. Simons Island. Starting with the godwits, they weigh each bird to determine if it is large enough to carry the 9.5-gram transmitter. They must weigh more than 300 grams to qualify. Two birds are selected.

The bird’s bills and a portion of their legs referred to as the tarsus are measured. Three feathers are plucked, two from the breast and one from the wing to be used for analysis. Tests that measure the ratio of stable isotopes can determine what the bird was feeding on when it grew the feather, giving researchers a more accurate picture of migration habits.

Wings are stretched to check for molting, which helps indicate the age of the bird, and then each leg receives both a metal band and a plastic band for identification. After a quick swab to test for avian influenza, volunteers photograph each bird and then finally it is released, its ordeal over.

The team works long into the evening, finishing as temperatures begin to drop into the 30s. The catch includes 11 marbled godwits and 44 American oystercatchers, a species listed as threatened in Georgia. Six of the oystercatchers and one godwit are re-captures, or birds previously banded. The re-captured oystercatchers include one from Virginia and one from North Carolina. The re-captured godwit had been banded in Georgia.

The Wildlife Resources Division has been banding marbled godwits and American oystercatchers since 2001. But researchers began the godwit transmitter project in Georgia last fall, thanks to a grant from The Environmental Resources Network, or TERN, the nonprofit advocacy group for Wildlife Resources’ Nongame Conservation Section.

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