Willet (Catoptrophorus semipalmatus)

Synonyms: Scolopax semipalmata, Tringa semipalmata
KingdomAnimalia
PhylumChordata
ClassAves
OrderCharadriiformes
FamilyScolopacidae
GenusCatoptrophorus (1)
SizeLength: 33 - 41 cm (2) (3)
Wingspan: 70 cm (4)
Weight173 - 375 g (2)

The willet is classified as Least Concern (LC) on the IUCN Red List (1).

A medium-sized shorebird with long legs and a long, straight beak, the willet (Catoptrophorus semipalmatus) is most easily recognised by its loud, ringing pill-will-willet call, and by the striking black and white pattern on its wings, which is only visible in flight (2) (3) (4). With the wings closed the willet is, in contrast, a rather drab grey to brownish-grey bird, with a white rump and tail, grey legs and a blackish beak (3) (4). During the breeding season, the head and body are covered in darker bars and streaks (3). The male and female willet are similar in appearance, but females tend to be slightly larger (2) (3). Juveniles resemble the non-breeding adult, but are more brownish, and the feathers on the back have light edges (2) (4).

The willet is divided into two subspecies, the eastern willet (Catoptrophorus semipalmatus semipalmatus) and the western willet (Catoptrophorus semipalmatus inornatus). In addition to having distinct breeding ranges and subtly different calls, the eastern willet is slightly darker and smaller than the western willet, and has a stouter bill and more streaked breeding plumage (2) (3) (4).

The willet breeds in North America and the West Indies, and winters from the United States south into South America (2) (3) (4) (5). Subspecies C. s. semipalmatus breeds along the Atlantic and Gulf coasts of North America and throughout much of the West Indies, and winters from coastal USA, through the Caribbean and Central America, into northern South America. C. s. inornatus breeds in inland wetlands of the Great Plains and Great Basin in western North America, wintering mainly from the Pacific coast of North America south to Chile, although some individuals migrate to the Atlantic and Gulf coasts for the winter (2) (3). The willet has also occasionally been recorded outside of its normal range, in Europe (3) (5).

The two subspecies of willet differ in their preferred breeding habitat: C. s. semipalmatus generally breeds in coastal habitats with short vegetation, such as salt marshes, and is only rarely found in freshwater habitats during the breeding season, while C. s. inornatus prefers wetlands and grasslands in prairies (2) (3). Outside of the breeding season, the willet may occur on salt marshes, mud flats (especially those bordered by mangroves), shorelines, and sandy or rocky beaches (2) (3).

The willet may feed both by day and by night, locating its prey using sight or touch. A wide range of foraging methods are used, including pecking at the ground, probing into mud with the beak, stalking prey in water, or moving the bill from side to side through the water. The diet of this species includes aquatic insects, molluscs, worms, crabs and small fish (2) (3).

The breeding season of the willet runs between April and July. The nest is built on the ground, usually hidden in dense grass, although it is sometimes placed in the open (2) (3). The willet is believed to be monogamous (2) (3) (6), and breeding pairs may remain together and even nest in the same location over a number of years (6). Both the male and female willet share in the incubation of the eggs, although the female usually incubates during the day and the male at night (2) (3) (6). Clutch size is typically 4, and the eggs hatch after 21 to 29 days (2) (3). The young willets are able to feed themselves from the day of hatching, and leave the nest after just one to two days (3). Although both adults care for the chicks, the female abandons the brood after about two weeks (3) (6), leaving the male to continue caring for the young for at least a further two weeks (3). The male may desert the young when they fledge, or may continue to protect them for up to one week afterwards (3). The willet first breeds at around two years old (2) (3), and has been recorded living for up to ten years in the wild (3).

The willet is a widespread and relatively abundant species which is not currently considered globally threatened (5), although it may potentially face some threats from pollution and the use of insecticides, collisions with power lines, the loss and degradation of wetland habitats, and increasing development at wintering and staging sites (important areas used during migration) (3). In the past, some of its populations declined due to hunting, egg collection and the conversion of wetlands and grassland to agricultural land (2) (3), but the overall population is now thought to be stable (5), and the willet generally shows a reasonable tolerance of human activities (2).

There are currently no known conservation measures targeting this widespread shorebird. However, it may receive some protection from its listing on Appendix II of the Convention on Migratory Species (CMS or Bonn Convention), which aims to conserve migratory species throughout their range (7). Recommended conservation measures for the willet include protecting native grasslands and wetlands, burying powerlines to prevent collisions, and protecting important coastal sites used by the willet during winter or on migration (3). The willet may also benefit from further research into its breeding biology, ecology, migration routes and local population trends, and further investigation into its major staging and wintering areas would help identify those sites most in need of protection (3).

To find out more about the willet and its conservation, see:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
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  1. IUCN Red List (December, 2010)
    http://www.iucnredlist.org/
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
  3. Lowther, P.E., Douglas III, H.D. and Gratto-Trevor, C.L. (2001) Willet (Tringa semipalmata). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/579/
  4. The Cornell Lab of Ornithology - All About Birds: Willet (December, 2010)
    http://www.allaboutbirds.org/guide/Willet/id
  5. BirdLife International (December, 2010)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=3031
  6. Howe, M.A. (1982) Social organization in a nesting population of eastern willets (Catoptrophorus semipalmatus). The Auk, 99: 88-102.
  7. Convention on the Conservation of Migratory Species of Wild Animals (December, 2010)
    http://www.cms.int/