Eccentric prairie shorebird, known for strangeness
There is a shorebird currently in our midst that possesses a rather impressive collection of offbeat behaviors. I was pleased to find a substantial number of them recently while conducting a shorebird survey for the U.S. Fish and Wildlife Service. This little prairie nester I'm referring to is the Wilson's Phalarope (Phalaropus tricolor). The word phalarope is based on Greek and loosely translates to "coot-footed." Meaning the bird has lobed feet (like a coot) allowing it to be a proficient swimmer.
There are only three species of Phalarope in the world and Wilson's is the only member of the family exclusive to the western hemisphere. It breeds across a large portion of central and western North America where it finds a suitable nest site on the ground near shallow sloughs and wetlands. Winter finds the Wilson's Phalarope enjoying the long sunny days in South America, mostly in the pampas of Argentina. During migration, huge numbers of these birds gather at large alkaline lakes such at Great Salt Lake and California's Mono Lake.
Only a tiny fraction of the world's bird species exhibit sexual role reversal but Wilson's Phalarope is one. Females are larger and more colorful than their male counterparts and possess nearly the same testosterone level. As a result, females take the initiative in courtship and, in a group, can be observed pursuing a single male on nesting grounds. Females also show aggression toward other females once a suitable mate is found. Male Wilson's Phalaropes tend to be rather passive. Once eggs are deposited in a nest, the male sits and incubates them. At this time the female leaves for good and begins migrating south, leaving the male to tend to the family brood.
Smaller and thinner bodied than a Killdeer, the Wilson's Phalarope female has black legs (in summer); gray on the crown, nape, back and upper wings; a white throat, breast and belly; and a wide dark eyeline that runs down its neck becoming a rich cinnamon color before wrapping around on its back and forming a "v." Both sexes have long, black needle-like bills. The male is much paler in all respects with only a pale reddish coloration in lieu of the cinnamon. In winter both appear in similar muted tones of gray and white with yellow legs.
Given their webbed toes, the Phalaropes are considered the most aquatic of the world's shorebirds. The Wilson's toes, however, are not fully lobed so the birds don't spend time in the oceans like their two cousins do. But swim they will and it's in water a somewhat comical behavior takes place. You may be excused for wondering just what the heck is going on when several hundred Wilson's Phalaropes are seen swimming frantically in individual circles. It is thought that this activity stirs up invertebrates from beneath the surface making them available to the floating bird to eat. Yet another strange activity practiced by these dainty shorebirds is commensal feeding. This is when one species benefits while the other incurs neither benefit nor cost. While feeding on shore, Wilson's Phalaropes have been known to associate closely with American Avocets. Out in the water, the bird sometimes swims with Northern Shovelers. Supposedly the much larger duck stirs up quantities of food, making it available to the Phalarope. In one study, commensal feeding with Shovelers proved three times more effective for the Phalaropes than when feeding alone.
This species is one of the more observable to the bird watcher. Check any piece of ponding water or sloughs. The best place to watch nesting behavior near us is any damp area of the Sheyenne National Grasslands. But if you want to see the colorful female you better hurry. By early June her work is done and she's heading south.