North Carolina plays a vital role in the life of dozens of species of migratory waterfowl in North America. But to find out just how well we are playing that important role, researchers have to count the birds.
Take, for example, the eastern population of tundra swans.
The birds get their name — tundra swan — from their home. Amazingly, the birds fly across the continent, from the tundras of Alaska and Western Canada, to spend the winter in North Carolina. The birds begin arriving in late October and stay through the middle of February.
The Tar Heel State winters more tundra swans than any other state on the East Coast. The roughly 70 to 75 thousand birds that migrate here each winter are drawn to the area by the abundant food sources found in the area’s lakes, sounds and farms. Most of the birds spend the winter months around the Pocosin Lakes National Wildlife Refuge near Plymouth in eastern North Carolina, where the refuge is managed specifically for migrating waterfowl.
North Carolina is the southernmost range for the migration. The remaining tundra swans in the population winter along the rest of the coast, from Pennsylvania to Virginia.
Biologists perform ground counts or aerial surveys of all the birds in the refuge on a bi-weekly basis. Elaine Barr, the biologist who performs the count, admits it’s impossible to individually count every bird. But with practice, she says it is possible to train your eyes to see groupings of birds, as well as patterns of birds and count quickly. For tundra swans, she counts in groupings of 100 birds at a time. When counting snow geese, the groupings start at 5000 birds.
Even though the bird count is an estimate, and not a precise count, it is still accurate enough for biologists to know if the refuge’s farmlands, wetlands and lakes are being managed correctly. For example, the bird count was higher the year a new wetlands area was opened. Biologists believe the new area attracted more birds.
In addition, biologists look at the count numbers over a long period of time to assess the health of the bird population and to determine if conservation efforts are succeeding. So far, the numbers continue to increase.
— Frank Graff
Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!