Wilson’s Phalarope is a shorebird sometimes seen at the Edmonds marsh in spring migration. It is a long-distance migrant, flying from as far away as the southern regions of South America to breed in the interior of Canada and the United States. Usually only one phalarope at a time visits the Edmonds marsh, and not every year. This spring saw the unexpected arrival of two females and a male that spent at least several hours wandering the mud and feeding on the water.
South America’s highland salty lakes are home to most of the Wilson’s Phalarope population in winter. While it will stop over on salt marshes and salty lakes in migration, its summer habitat includes shallow freshwater prairie lakes and freshwater marshes and mudflats. In migration, the largest concentrations of Wilson’s Phalarope can be found on salty or alkaline lakes such as California’s Mono Lake and the Salton Sea.
Diet is mostly aquatic insects and crustaceans. This phalarope also eats shrimp, copepods, and seeds of marsh plants. During autumn and winter it mostly feeds on brine shrimp and brine flies on salty lakes. Brine shrimp are an abundant species in Mono Lake and most likely account for its importance in migration. In spring, this phalarope only molts into its breeding plumage once it arrives on salty lakes in the Western U.S. At that time this species will eat enough to double its body weight, sometimes becoming so heavy that it cannot fly. It forages by swimming, spinning in circles to bring food to the surface, or near the surface, of the water where it can pick it up with its bill.
The Wilson’s Phalarope breeds from Eastern Washington to the Great Lakes along the northern latitudes of the U.S. In Canada, it breeds from the interior of British Columbia east to the prairies of Manitoba. In all three of the Western Hemisphere’s phalarope species, the female is larger than the male and much more colorful. In contrast to most bird species, female phalaropes compete for males. The courtship display of the female Wilson’s Phalarope includes stretching her neck, puffing out the neck feathers, and making a chugging call.
The female may take the lead in selecting a nest site but the male finishes nest construction. The nest is a shallow depression lined with grass, located near water and protected by marsh plants. Soon after the female lays four eggs, she leaves them to the male while she seeks out another male to mate with. The male incubates the eggs for about 23 days. The young hatch with their eyes open and fully feathered. Although the male tends them while they are small, the young find all of their own food. This species nests close together in small loose colonies.
Wilson’s Phalarope migrates in flocks. In fall migration, after it leaves its Western U.S. staging areas, it may fly nonstop to its South American wintering grounds. There are many collective nouns for a group of any phalaropes. Some of them include a dopping, swirl, twirl, whirl, and whirligig. A short You Tube video shows how this species spins while feeding: https://www.youtube.com/watch?v=heEUPbxmYgQ.
The Wilson’s Phalarope population has remained level or declined only slightly since 1966, according to the North American Breeding Survey. The population is estimated at 1.5 million. It is dependent upon wetland habitat, water quality, and the availability of surface water. Drainage of prairie potholes can affect the population. Changes to Mono Lake and the Salton Sea could have an outsized effect on the population since both are critical staging grounds for migration.
This is the call of a preening female Wilson’s Phalarope, responding to the flyover of another phalarope: https://www.xeno-canto.org/294469.
(It is my hope that regular readers of Bird Lore are gaining a new appreciation of the importance of the Edmonds marsh to the diversity of birds seen in our community. Many of the species may only be seen once or twice a year, or once every several years. That does not undercut the marsh’s importance to our community and to the birds that use it. The diversity of bird species that pass through Edmonds, compared to surrounding communities, is outsized because of the marsh. Preservation and restoration of the marsh, which is now about one quarter of its original size, may increase bird diversity in Edmonds.)
— By Carol Riddell
Carol Riddell manages the bird education displays, on behalf of Pilchuck Audubon Society and Edmonds Parks & Recreation, at the Olympic Beach Visitor Station.