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Catoptrophorus semipalmatus

What do they look like?

Willets are large, long-legged shorebirds. They are grey or brown overall and they have a distinctive white rump and broad, white wing stripe visible when they are flying. They are 33 to 41 cm long and from 200 to 330 grams. Sexes are similar in color, but females are slightly larger. There are two populations of willets that differ in distribution, ecology, and appearance. Western willets, which breed in western North America, are larger and paler, eastern willets, which breed in eastern North America, are slightly smaller and darker overall. The sounds they make and their habitats differ also. Their bill and legs are grayish, but vary from light to dark. The toes are slightly webbed.

  • Sexual Dimorphism
  • female larger
  • Range mass
    200 to 330 g
    7.05 to 11.63 oz
  • Range length
    33 to 41 cm
    12.99 to 16.14 in

Where do they live?

Willets are widespread in the Americas. They are found in sandy beaches and wetlands in coastal and inland areas during the winter and breeding seasons from southern Canada and northern California south to Venezuela, Brazil, and Uruguay. They are occasionally seen in Europe and the Hawaiian Islands.

What kind of habitat do they need?

Willets are found in a wide variety of coastal habitats in winter, during migration, and during breeding season, including sandy coastlines, mudflats, and rocky intertidal zones. Western willets breed in wetlands and grasslands near water and with sparse vegetation, including croplands. They are also found along lakeshores and on salt or alkali flats. Eastern willets breed in coastal marsh and wetland habitats, including salt marshes and beaches.

  • Aquatic Biomes
  • temporary pools
  • coastal

How do they reproduce?

Willets for mated pairs that last for many years, even for their whole lives. Mated pairs are not found together throughout the year, but they find each other again at the start of the breeding season. They use displays and calls to re-establish their relationship and begin nesting. They fly with their wings held high above their heads and flutter their primary feathers. Females fly to the male and hover beneath him while they sing to each other. They then slowly fly to the ground together.

Willets breed from May through July. Once pairs have formed, they begin to search for a nest site together. Nests are simple scrapes that are lined with grass. Willets have one brood yearly. Females lay 4 greenish eggs. Incubation is 22 to 29 days, averaging 25. Young willets generally can fly about 4 weeks after hatching. Males and females breed as early as their 2nd year.

  • How often does reproduction occur?
    Willets breed once yearly.
  • Breeding season
    Willets mate in May and June.
  • Range eggs per season
    3 (low)
  • Average eggs per season
  • Range time to hatching
    22 to 29 days
  • Average time to hatching
    25 days
  • Average fledging age
    4 weeks
  • Average time to independence
    4 weeks
  • Range age at sexual or reproductive maturity (female)
    2 (low) years
  • Range age at sexual or reproductive maturity (male)
    2 (low) years

Both males and females incubate eggs and protect the young. Young are able to walk and feed themselves within hours of hatching. Hatchlings leave the nest within a day of hatching. Females stay with the young for up to 2 weeks, males for 4 weeks or more.

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • protecting
      • male
      • female

How long do they live?

The oldest recorded willet in the wild was 10 years and 3 months old. Eggs and nestlings may be lost to predators, severe weather, or high tides.

  • Range lifespan
    Status: wild
    10.25 (high) years

How do they behave?

Willets can be active at any time of the day, they take advantage of tides and moonlight to find prey. Willets use their long legs to run after prey. They fly relatively low and will occasionally swim. They are found in small groups, except during the breeding season. Some willet populations are resident year-round, such as those in the Antilles or in California. Other populations migrate short to long distances. Eastern willets migrate along coastlines. Western willets migrate along the Mississippi River and over other inland areas. Willets migrate at night in small groups.

Home Range

Willets aggressively defend territories during the breeding season. Few studies have estimated home range, but a Florida study suggested that home range sizes were 0.26 to 5.90 square km.

How do they communicate with each other?

Willets are known for their "pill-will-willet" call. This call is used to define territories and in mating displays. Willets use a repertoire of other calls, from high pitched squeaks of the young to appeasement calls (Kyah-yah), clicks, clucks, honks, and screams.

What do they eat?

Willets eat many kinds of invertebrates, depending on what is found in the local area. They eat insects, crustaceans, molluscs, worms, and occasional fish. Willets feed at all times of the day, depending on tide patterns and moonlight. They chase prey down visually and use their bills to probe for prey in sand and mud or turn over objects to find prey underneath. They also walk through shallow water with their bills open and held in the water to hunt by touch.

  • Animal Foods
  • insects
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans

What eats them and how do they avoid being eaten?

Willets use calls to warn others of predators and they will come together to mob predators. During nesting, willet parents defend their young and will attack predators. When a hawk or falcon is hunting, willets sometimes crouch or hide, rather than flying. Most predation on willets is on eggs and young. Adults are mainly taken by raptors or terrestrial predators when they are on a nest. Reported predators on eggs include northern harriers, Cooper's hawks, red-shouldered hawks, fish crows, common ravens, American crows, raccoons, red foxes, coyotes, rat snakes, and feral dogs. Fish crows and American crows hunt in groups of 3 for willet nests and cooperate to drive off adults while they take the eggs. Adults and young are taken by Swainson's hawks, northern harriers, peregrine falcons, red-tailed hawks, Cooper's hawks, and herring gulls. There are many other potential predators, including other raptors, snakes, and terrestrial predators, such as mink, otters, and skunks.

What roles do they have in the ecosystem?

Willets compete directly for food with a wide variety of similarly-sized shorebirds and often interact aggressively over food and space. They have been recorded competing with long-billed curlews, least sandpipers, common terns, least terns, American crows, Wilson's phalaropes, greater yellowlegs, killdeer, dowitchers, Wilson's plovers, fish crows, marbled godwits, and gulls. Willets are parasitized by a wide variety of internal parasites, including numerous species of flukes, tapeworms, roundworms, and spiny-headed worms.

Species (or larger taxonomic groups) that are mutualists with this species
Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

There are no adverse effects of willets on humans.

How do they interact with us?

Willets were once eaten and eggs and young were collected for markets. They are interesting and charismatic shorebirds.

  • Ways that people benefit from these animals:
  • food

Are they endangered?

Willets have a large geographic range and relatively large population sizes. There don't seem to be any significant declines in population recently. They are considered "least concern" by the IUCN and are protected by the U.S. Migratory Bird Act. However, the habitats they depend on for breeding, migration, and wintering are being destroyed and contaminated. Grassland and coastal marsh habitats, which willets use for breeding, are especially endangered.

Some more information...


Tanya Dewey (author), Animal Diversity Web.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.


an animal that mainly eats meat


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.


active at dawn and dusk

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

  1. active during the day, 2. lasting for one day.

animals that generate their own body heat through metabolic processes.


an area where a freshwater river meets the ocean and the fresh and saltwater mixes


A substance that provides both nutrients and energy to a living thing.


mainly lives in water that is not salty.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


makes seasonal movements between breeding and wintering grounds


eats mollusks, members of Phylum Mollusca


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

uses sight to communicate

young precocial

young are relatively well-developed when born


Lowther, P., H. Douglas. 2001. Willet (Catoptrophorus semipalmatus). The Birds of North America Online, 579: 1-20. Accessed April 15, 2009 at

University of Michigan Museum of ZoologyNational Science Foundation

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Dewey, T. 2009. "Catoptrophorus semipalmatus" (On-line), Animal Diversity Web. Accessed April 17, 2014 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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