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Wilson's Phalarope

Phalaropus tricolor ORDER: CHARADRIIFORMES FAMILY: SCOLOPACIDAE

IUCN Conservation Status: Least Concern

Every year in late summer, migrating Wilson's Phalaropes put on an amazing show as enormous flocks amass on salty lakes of the West. There they spin round and round in the nutrient-rich waters, creating whirlpools that stir up invertebrates that will fuel their migration to South America. Females are rich peachy and gray, and are more colorful than the males. Females court and defend male mates—several per season—while males do most of the work of raising the young.

At a GlanceHelp

Measurements
Male
Length
8.7–9.4 in
22–24 cm
Wingspan
15.4–16.9 in
39–43 cm
Weight
1.3–3.9 oz
38–110 g
Female
Weight
1.8–4.5 oz
52–128 g
Relative Size
Larger than a Least Sandpiper; smaller than a Killdeer.
Other Names
  • Falaropa de Wilson (Spanish)
  • Phalarope de Wilson (French)

Cool Facts

  • Unlike most birds where the female has the predominant role in caring for young, female phalaropes desert their mates once they’ve laid eggs. While the male raises the young by himself, the female looks for other males to mate with. This unusual mating system is called polyandry, and it’s reflected in the way the two sexes look, with the females more brightly colored than the males.
  • Wilson's Phalaropes are one of only two species of shorebirds that molt at resting sites on the migration pathway, rather than on the breeding grounds before leaving or on the wintering grounds.
  • While stopping over to molt on salty lakes in the West, Wilson's Phalaropes usually eat so much that they double their body weight. Sometimes they get so fat that they cannot even fly, allowing researchers to catch them by hand.
  • Wilson's Phalaropes almost always lay a clutch of exactly four eggs.

Habitat


Lake/Pond

Wilson's Phalaropes breed in wetlands, upland shrubby areas, marshes, and roadside ditches. During migration, most individuals stop over at saline lakes in western North America, as well as coastal marshes and sewage ponds. Their winter habitat consists of high Andean salt lakes as well as wetlands in southern South America.

Food


Insects

Wilson's Phalaropes mainly eat small aquatic invertebrates such as midges and shrimp. While foraging in the water, they often spin in circles to create a whirlpool that sucks up food items to the surface of the water. Other techniques include chasing and pecking prey from the surface of mud or water, standing still and stabbing at passing flies, and probing inside mud.

Nesting

Nesting Facts
Clutch Size
4 eggs
Number of Broods
1 broods
Egg Length
1.3–1.4 in
3.2–3.5 cm
Egg Width
0.9–0.9 in
2.3–2.4 cm
Incubation Period
18–27 days
Nestling Period
1 days
Egg Description
Buffy, covered with brown blotches.
Condition at Hatching
Fully feathered and eyes open, able to feed themselves.
Nest Description

The female lays her eggs in nothing more than a scrape on the ground. Later, the male tidies the scrape and arranges the surrounding vegetation to hide the nest.

Nest Placement

Ground

The female usually chooses a site around the edge of a wetland or in surrounding upland vegetation.

Behavior


Dabbler

Phalaropes are unusual in that their mating system is polyandrous, meaning females usually mate with multiple males. Females vie for males with aggressive postures involving jutting the head back and forth, sometimes breaking into fights. Once the female acquires a mate, she begins to use courtship displays involving bowing and upright postures to initiate copulation. Soon after laying a complete clutch, the female usually abandons the male to seek out another male to mate with. Wilson's Phalaropes are very social throughout the year. They nest relatively close together in small, loose colonies, and during migration they travel in large flocks. Predators include garter snakes, gulls, crows, blackbirds, skunks, ground squirrels, and racoons.

Conservation

status via IUCN

Least Concern

Wilson’s Phalarope numbers have remained level or declined slightly since 1966 (less than 1% per year), according to the North American Breeding Survey. A 2012 assessment estimated their population at 1.5 million breeding individuals, although it noted a lack of data and based this estimate on a 2006 study. Wilson’s Phalaropes breed across the Great Plains and intermountain West, and their numbers dropped sharply in the early twentieth century as wetlands in these regions were altered. They are still dependent on wetland habitat, water quality, and the availability of surface water. On migration they stage in huge numbers at hypersaline lakes such as Mono Lake and the Salton Sea. Because so many birds congregate, changes to these areas including water diversion and reclamation could have serious repercussions.

Credits

  • Colwell, M.A., and J.R. Jehl, Jr. 1994. Wilson’s Phalarope (Phalaropus tricolor). In The Birds of North America Online, No. 83 (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York.
  • Andres, B.A., P.A. Smith, R.I.G. Morrison, C.L. Gratto-Trevor, S.C. Brown, and C.A. Friis. 2012. Population estimates of North American Shorebirds, 2012. Wader Study Group Bulletin 119:178–194. Available from the U.S. Shorebird Conservation Plan website.
  • Dunne, P. 2006. Pete Dunne’s essential field guide companion. Houghton Mifflin, Boston.
  • Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder’s handbook. Simon & Schuster Inc., New York.
  • IUCN. 2012. IUCN Red List of Threatened Species (ver. 2012.1).
  • North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014 Report. U.S. Department of Interior, Washington, DC.
  • O’Brien, M., R. Crossley, and K. Karlson. 2006. The Shorebird Guide. Houghton Mifflin, New York.
  • Sibley, D.A. 2014. The Sibley guide to birds, second edition. Alfred A. Knopf, New York.
  • USGS Patuxent Wildlife Research Center. 2014. North American Breeding Bird Survey 1966–2014 Analysis.

Range Map Help

Wilson
View dynamic map of eBird sightings

Migration

Long-distance migrant. Females depart breeding areas first, followed by males and finally juveniles. All birds stop for several weeks during migration at saline lakes to take advantage of abundant invertebrate food. By mid-September, they are in South America—in high-elevation lakes in the Andes, as well as in the Patagonian lowlands and Tierra del Fuego.

Find This Bird

To find Wilson’s Phalaropes on their breeding grounds, visit small marshes and shallow wetlands and look out for these small, fairly long-legged birds. At this time of year they may be behaving like “normal” shorebirds, walking on land or in shallow water as they tend their ground nests. During migration, look for them in sometimes enormous numbers at places like Mono Lake, the Salton Sea, or the Great Salt Lake, as well as sewage ponds and smaller wetlands. Here they’ll be acting very unlike a shorebird—swimming in deeper water, where their small size, angular shape, needle-like bills, and habit of spinning in circles should help you pick them out.

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