Merlin

Whimbrel Life History

Habitat

Habitat Shorelines

On their wintering grounds, Whimbrels feed mostly on tidal mudflats and sandflats; they also forage in saltmarshes, lagoons, estuaries, and on reefs and rocky shorelines where small crabs are available. In some tropical areas, hard mudbanks and mangrove swamps attract Whimbrels. When not feeding, Whimbrels roost in flocks in marshes, meadows, fields, dunes, and oyster beds, as well as on small islands and even in mangrove trees. Migrating Whimbrels also use these habitats, along with coastal tundra and heath in Alaska and Canada. North American Whimbrels breed in subarctic and alpine tundra and taiga. In some places, they nest in drier upland environments (heath), where berry-bearing shrubs abound, but over much of the breeding range they use wetter lowlands with grasses, sedges, mosses, lichens, small shrubs, and stunted trees.

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Food

Food Aquatic invertebrates

Whimbrels feed on marine invertebrates in intertidal zones. In saltmarshes and mudflats they eat fiddler crabs, which they hunt visually, first locating the entrance to the crab’s burrow in the mud, then extracting it using their long bills. In similar manner, they capture swimming crabs, mud crabs, crayfish, mole crabs, small fish, marine worms, sea cucumbers, sand shrimp, and small mollusks such as coffee bean snails. After extracting a crab from the burrow, Whimbrels rinse it to remove mud and usually remove the largest claw before consuming it. In migratory stopover areas, as well as on the wintering grounds, Whimbrels maintain feeding territories, which they defend occasionally if another Whimbrel comes too close. Arriving on the breeding grounds, Whimbrels eat many sorts of berries left over from the previous summer, among them cranberry, blueberry, bearberry, and crowberry. In fall migration, the Whimbrels that move toward the Canadian Maritimes feed heavily on these same berries, along with huckleberry and cloudberry, plucking them with the bill tip and tossing them back to swallow. Throughout the year, Whimbrels also eat spiders and various insects, including flies, beetles, and grasshoppers, when available.

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Nesting

Nest Placement

Nest Ground

Nests are built on raised sites such as a hummock or small ridge, usually near a shrub to offer shelter from wind; such sites are drier than surrounding areas and usually have better visibility.

Nest Description

Nests are simple bowls that are pressed into the ground, then lined with leaves of surrounding vegetation, along with some grasses or lichens. The interior of the bowl averages about 5.6 inches across and 1.5 inches deep.

Nesting Facts
Clutch Size:2-4 eggs
Number of Broods:1 brood
Egg Length:2.0-2.6 in (5.14-6.59 cm)
Egg Width:1.4-1.7 in (3.55-4.28 cm)
Incubation Period:22-28 days
Egg Description:

Blue-green to brownish or buff.

Condition at Hatching:

Downy and active, may leave nest within one to two hours.

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Behavior

Behavior Ground Forager

Whimbrels are a joy to experience on the breeding grounds, where the male performs dramatic aerial song flights. Ascending sharply as high as 1,000 feet, he begins to fly in large circles, gliding downward and then climbing back upward with exaggerated movements, singing during the glides. Such displays happen mostly early in the breeding season, before nesting begins, and probably serve to attract mates and warn off rival males. Courting males chase females on foot and in flight, and receptive females respond by drooping the wings, cocking the tail, and leaning forward. Pairs may also perform alternating displays involving raised tail and lowered breast. They maintain their bond with trilling calls during incubation duties, which they share. Whimbrels are monogamous during the nesting season and often return to the same area to nest with the same mate in successive seasons. They nest in loose associations of a few pairs, and neighbors tend to tolerate the presence of other neighbors that cross their territories; however, both male and female of a pair will drive out other Whimbrels by threat displays, with raised wings and brisk running, or with rapid aerial pursuit and whining calls. They also pursue other large shorebirds, such as godwits and Bristle-thighed Curlews, that happen into their territory. Territory size varies greatly, from about 12 acres to over 90 acres, but territorial defense wanes once the eggs hatch. Whimbrels also maintain mobile feeding territories, but conflicts between feeding birds are typically brief and infrequent, involving chasing and calling, seldom physical contact. Whimbrels migrate and roost in flocks, often accompanied by smaller shorebird species.

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Conservation

Conservation Low Concern

Because Whimbrels nest in remote areas, information about their population trends is lacking. Partners in Flight estimates the global breeding population at 1.8 million. The species rates a 12 out of 20 on the Conservation Concern Score, indicating it is a species of low conservation concern. Whimbrels were heavily hunted in North America for food through the early twentieth century and are still hunted in parts of South America and the Caribbean. Other threats to this species include the destruction or modification of coastal wetland habitats, environmental contamination, and sea-level rise, which will threaten its wintering and stopover habitats in particular.

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Credits

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

Skeel, Margaret A. and Elizabeth P. Mallory. (1996). Whimbrel (Numenius phaeopus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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