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Tuesday, August 15, 2006

Birds of the Mid-Atlantic #20: Yellowlegs

Fall migration is already upon us. In fact, it has been upon us for about a month now. Like spring migration, fall migration proceeds in a series of stages, with certain species or families dominating each stage. In contrast to spring migration, fall migration is less compressed, occurring over a period of about five months, as opposed to the three months of spring migration.

August is the time for shorebirds to move through the Mid-Atlantic region. The best way to experience shorebird migration is to visit one of the many large refuges along the Atlantic coast, as I did on Saturday. If you are stuck inland, there are still opportunities to see shorebirds as they pass through the area. (See, for example, this list of Maryland shorebird sites.) While species diversity is more limited, inland sites often provide an opportunity to study birds up close, without the need for a spotting scope. Shorebirds that commonly occur inland include the subjects of today's essay, greater and lesser yellowlegs.

Yellowlegs are the graceful counterparts to the many squat or chunky members of the sandpiper family. Unlike most other shorebirds, they have long yellow legs and elegantly-shaped head and neck. Their long legs allow them to wade out into deeper water where other shorebirds cannot go. There they hunt for insects and crustaceans, as well as an occasional small fish.

Greater Yellowlegs / Photo by USFWS

Greater and lesser yellowlegs have almost identical plumage, so a birder needs to pay attention to structural characteristics to make an identification. When the two species are next to each other, the size difference is apparent. On average, the greater yellowlegs is 3-4 inches larger than the lesser. With a single bird, or single-species flock, this is not so useful. Luckily, the bill can help answer the question. A lesser yellowlegs has a bill that is slightly longer than the head (minus the bill). Greater yellowlegs have bills that are 1.5-2 times longer than the head; their bills are also thicker and slightly upturned. Calls are another clue; the greater yellowlegs tends to give three-note calls (dew-dew-dew) while lesser yellowlegs whistle once or twice (tu-tu).

Lesser Yellowlegs / Photo by USFWS

Both yellowlegs species winter primarily in Central and South America. However, at least a few of each species winter in the southern United States and along the Atlantic coast.

To find shorebirds away from the coast, look for wet fields, pond and lake edges, and mudflats. Other common shorebirds that may occur at inland sites include killdeer, semipalmated plover, spotted sandpiper, solitary sandpiper, least sandpiper, semipalmated sandpiper, and western sandpiper. In Washington, DC, the best shorebird sites are the parks along the Anacostia River; nearby, there are good spots at Hunting Creek and Cameron Run in Virginia.

Crossposted at A DC Birding Blog.



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