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Wilson's Phalarope
Steganopus tricolor
Family: PHALAROPODIDAE
Order: Charadriiformes
Spanish Common Name: Falaropo de pico largo; Falaropa de Wilson; Falaropo tricolor; Chorlillo nadador; Amacozque
French Common Name: Phalarope de Wilson
(c) Jim Fenton |
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Natural History
Appearance
The Wilson's Phalarope is a slender, delicately built shorebird with a small head, and thin, pointed bill. Breeding females are quite colorful, with a gray cap, white eyebrow, and dark crimson mask that extends from the bill to the back of the head and then swoops down the nape toward the back. The throat is white; a rusty wash colors the neck and chest. Otherwise, the female is whitish below and grey above. Males are pale grey above and whitish below, with a light rusty wash on the nape of the neck. In winter, both sexes have grey-white plumage without any warm colors. These medium-sized shorebirds average 2.1 ounces in weight and 8.5 inches in length, with pointed wings that span 17 inches. Females are substantially larger and can weigh as much as 40% more than males.
Habitat
The Wilson's Phalarope breeds in the wetlands of North America's Great Plains and northern Rocky Mountains, favoring shallow water with adjacent mudflats and wet grasses. In migration and during winter, this shorebird prefers the shallows of salt lakes and ponds.
Feeding
Like other phalaropes, the Wilson's often spins on the water, at speeds of up to 60 turns per minute. The purpose of this whirling behavior may be to churn the muddy bottom, excite small aquatic creatures, and condense them in the swirls, where they can be picked off the surface. Wilson's phalaropes consume flies, beetles, brine shrimp, and other tiny marine creatures.
Reproduction
Compared to other shorebirds, the Wilson's Phalarope has reversed many typical sexual roles. Females display brighter plumage, court and defend mates, fight off other females, and provide almost no care for eggs or young. During migration and in loose breeding colonies, non-territorial females gather in small groups to court an available male. The females display with exaggerated postures and a "chug" call. After bonding, pairs stay together until the eggs are laid. Females are then free to court other males.
The pair begins construction on a simple nest, which the male completes. The female lays four buff-colored eggs, marked with brown. Under the male's care, they hatch in 18 to 27 days. During incubation, females defend the nest by pretending to incubate a false "nest." Males distract intruders by acting injured. Within an hour of hatching, the fully feathered chicks can walk, swim, and feed independently, but require brooding to keep them warm. Researchers have not yet observed the juvenile stages of Wilson's Phalaropes.
Migration
From the breeding grounds, Wilson's Phalaropes migrate in segregated groups: females depart first, followed by males, and finally, juveniles. All three groups stage at North American salt lakes before their non-stop flight to southern South America. Spring migration progresses through the mountains of South, Central, and North America to Cheyenne Bottoms, Kansas, where nearly all Wilson's Phalaropes stage.
References
Colwell, M. A. and J. R. Jehl, Jr. 1994. Wilson's Phalarope (Phalaropus tricolor). In The Birds of North America, No. 83 (A. Poole and F. Gill, eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
Nicholoff, S. H., compiler. 2003. Wyoming Bird Conservation Plan, Version 2.0. Wyoming Partners in Flight. Wyoming Game and Fish Department, Lander, WY.
Sibley, David Allen. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.
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