American Avocet Life History

Habitat

Habitat Marshes

American Avocets forage in shallow fresh and saltwater wetlands, salt ponds, impoundments, and evaporation ponds. They nest in areas with little or no vegetation along dikes and islands. During winter they also use intertidal mudflats, tidal lagoons, brackish impoundments, sewage ponds, rice fields, and flooded pastures.

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Food

Food Aquatic invertebrates

American Avocets forage for aquatic invertebrates in shallow water while wading or swimming. Their diet consists of beetles, water boatmen, midges, brine flies, fairy shrimp, water fleas, amphipods, and more. They also eat small fish and seeds from aquatic plants. They capture aquatic invertebrates in the water column by sweeping their bill side to side, a signature behavior called scything. With each step they put their slightly open bill in the water and move it in the direction of the outstretched foot, alternating sides with each step. They also capture prey by pecking and plunging. Pecking involves lunging out with their bill to peck at prey within the water column or in the wetland bottom. Individuals also plunge their head and neck underwater to grab prey in the water column. Foraging methods vary by time of day, flock size, and date. Scything and pecking occur more often during the day, while plunging is more common at night.

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Nesting

Nest Placement

Nest Ground

Male and female avocets select a nest site together. The male leads the female around making scrapes in the ground, until they both choose a spot to nest. They typically nest on islands or dikes, placing the nest on the ground with little or no surrounding vegetation.

Nest Description

The male or female makes a scrape in the ground with their breast and feet. They line the shallow depression with grass or other vegetation, feathers, pebbles, or other small objects, but sometimes the nest is completely unlined. Additional lining may be added to the nest throughout incubation, especially if rising waters threaten to flood the nest.

Nesting Facts
Clutch Size:3-4 eggs
Number of Broods:1 brood
Egg Length:1.6-2.4 in (4.2-6 cm)
Egg Width:1.1-1.8 in (2.9-4.6 cm)
Incubation Period:18-30 days
Egg Description:

Greenish brown with irregular dark spots. Pointed on one end.

Condition at Hatching:Downy and able to walk.
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Behavior

Behavior Probing

American Avocets wade in shallow wetlands often less than 8 inches deep, but they also swim in deeper waters. On the breeding grounds, avocets breed in loose colonies and defend the nest site. Intruders are met with outstretched necks or a crouch-run where they ruffle their feathers, crouch down, and run at the intruder. Upon the approach of a terrestrial predator, they may approach with a teetering gait and outstretched wings, as if on a tightrope. They also try to distract the predator by crouching on the ground as if incubating, only to move and crouch again in a new location. In its pre-copulation display, the male American Avocet preens himself with water, gradually gaining intensity to the point of frenzied splashing just before mating with the female. After mating, the pair intertwines their necks with their bills crossed and runs forward. The pair stays together for a single breeding season. One notable display, known as “circling,” occurs before and during nesting and involves two pairs, or a pair and a third individual. Individuals face each other in a circle and stretch their bills toward each other while calling and rotating in a circle. On the wintering grounds they forage and rest in flocks often with other shorebirds, especially the Black-necked Stilt.

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Conservation

Conservation Low Concern

American Avocets are common and their populations have been stable between 1966 and 2015, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 450,000. The species rates an 11 out of 20 on the Continental Concern Score, which means it is not on the Partners in Flight Watch List and is a species of low conservation concern. People drained or converted wetlands on a large scale in the early twentieth century, causing population declines as traditional breeding sites were eliminated. Creation of sewage ponds, agricultural evaporation ponds, rice fields, and salt ponds now provide additional breeding habitat to counteract past losses. Many wetlands in the western United States however, are contaminated with selenium that leaches from the soil following irrigation, which can cause low reproductive success and embryo deformities. Methylmercury, a pollutant associated mainly with the burning of coal, also causes chick deaths in some wetlands.

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Credits

Ackerman, Joshua T., C. Alex Hartman, Mark P. Herzog, John Y. Takekawa, Julie A. Robinson, Lewis W. Oring, Jospeh P. Skorupa and Ruth Boettcher. 2013. American Avocet (Recurvirostra americana), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Lutmerding, J. A. and A. S. Love (2016). Longevity records of North American birds. Version 2016.1. Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, USA.

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

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

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

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