American avocets are very beautiful birds with personality! I worked near them at wetland and they are very vocal and protective of nests. It is interesting to watch them wade and feed in shallows.
American avocets are mostly quiet and uncaring but become extremely aggressive on breeding and nesting grounds and protest loudly and dive bomb when intruders approach. They have few non-human predators, some known nest predators include skunks (subfamily Mephitinae) and foxes (family Canidae).
Known Predators:
Graceful and sleek, these long-legged waders have a black bill and light blue legs. Avocets are the tallest and longest-legged birds in their family. They are 400 to 500 mm in length and have a wingspan of 213 to 242 mm. They are often confused with black-necked stilts (Himantopus mexicanus), but are distinguishable by the bold black and white pattern on their back and wings and a strongly upcurved black bill. Females are similar in appearance to males but with a shorter and more upwardly-curved bill, male bills are longer and straighter. They are the only avocet with distinct breeding and non-breeding plumages. Breeding plumage is obtained in the first year and is a beautiful rusty cinnamon along the head and neck. Basic plumage is a gray head. Adult breeding plumage appears from January to March and is lost in July to September.
Average length: 400-500 mm.
Average wingspan: 213-242 mm.
Sexual Dimorphism: sexes shaped differently
Other Physical Features: endothermic ; bilateral symmetry
Average mass: 340 g.
Banded American avocets have been recorded to live up to 9 years in the wild.
No records are available about life span in captivity, but presumably they live for 9 plus years!
Range lifespan
Status: wild: 9 (high) years.
Average lifespan
Status: wild: 168 months.
American avocets are numerous in mudflats, ponds, wetlands, and freshwater marshes and swamps. They are also common in lakes, rocky/sandy seashores, bay/coastal islands, and tidal flats.
Habitat Regions: temperate ; tropical ; terrestrial
Aquatic Biomes: lakes and ponds; coastal ; brackish water
Wetlands: marsh ; swamp
Other Habitat Features: estuarine
American avocets are found in western North America from March through October and in coastal California, southern Texas, Florida, Louisiana and south to Guatemala in winter.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
American avocets swoop their open bills back and forth in shallow water to catch aquatic insects. They may feed in flocks of up to 100 plus birds, in deep water they will "tip up" like dabbling ducks and are reportedly good swimmers.
Foods eaten include: Insects and other invertebrates, shrimp and other crustaceans, aquatic vegetation and seeds.
Animal Foods: insects; terrestrial non-insect arthropods; aquatic crustaceans
Plant Foods: leaves; seeds, grains, and nuts
Primary Diet: omnivore
American avocets are important members of their ecosystem; because of their food habits they likely have a regulatory influence on insect and crustacean populations, and they are an important food source for their predators. They also have an influence on the plants and seeds they eat.
American avocets are enjoyable to watch and are sought out by many birders.
Positive Impacts: ecotourism
There are no known adverse affects of American avocets on humans.
1 brood per year, usually 3-5 eggs laid which are a pale ashy-yellow or olive-brown covered evenly with dark brown spots and blotches. Eggs are laid at intervals of 1-2 days, with a full clutch in 5 days (Hayman et al., 1986; Soothill & Soothill, 1982; Nethersole-Thompson, 1986).
Currently protected by the US Migratory Bird Act, American avocets are making a comeback after over-hunting in the 19th and early 20th centuries. The main threats to American avocets today are habitat loss and degredation.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
American avocets make loud "wheet" or "pleeet" and shrill "kleeap" sounds that are often repeated. They are very noisy when intruders approach active nests. They also communicate using complex displays that include dancing, bowing and crouching.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
American avocets are monogamous and loosely colonial. Pairs perform elaborate courtship displays that involve various crouching and bowing postures in and out of water, dancing with outspread wings and swaying from side to side.
Mating System: monogamous
Breeding occurs between April and June. Nests are built on shore and are usually scrapes in the ground; they are sometimes lined with dry grass or mud chips. The female lays 3 to 5 eggs (4 on average); eggs are olive colored with brown and black spots. Incubation lasts 22 to 29 days and the eggs hatch synchronously. Fledging occurs after 28 to 35 days.
Breeding season: April to June
Range eggs per season: 3 to 5.
Range time to hatching: 22 to 29 days.
Range fledging age: 28 to 35 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Average eggs per season: 4.
Both male and female American avocets incubate the eggs. Incubation lasts 22 to 29 days. The precocial young are cared for by both sexes but the young feed themselves. Fledging occurs after 28 to 35 days.
Parental Investment: no parental involvement; precocial ; pre-fertilization; pre-hatching/birth (Protecting: Male, Female); pre-weaning/fledging (Protecting: Male, Female)
The American avocet (Recurvirostra americana) is a large wader in the avocet and stilt family, Recurvirostridae, that is found in North America. It spends much of its time foraging in shallow water or on mud flats, often sweeping its bill from side to side in water as it seeks its crustacean and insect prey.
The American avocet was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the pied avocet in the genus Recurvirostra and coined the binomial name Recurvirostra americana.[2] Gmelin based his description on that by the English ornithologist John Latham who in 1785 had described and illustrated the American avocet in his A General Synopsis of Birds.[3] Latham cited the earlier publication by William Dampier and also that by Thomas Pennant.[4][5] The genus name combines the Latin recurvus meaning 'bent' or 'curved backwards' with rostrum meaning 'bill'.[6] The species is monotypic: no subspecies are recognised.[7]
The American avocet is a member of the order Charadriiformes, which includes shorebirds, gulls, and alcids. Its family, Recurvirostridae, includes stilts and avocets. The genus Recurvirostra includes three other species: the Andean avocet, the pied avocet, and the red-necked avocet.[7]
The American avocet measures 40–51 cm (16–20 in) in length, has a wingspan of 68–76 cm (27–30 in) and weighs 275–420 g (9.7–14.8 oz)[8][9] The bill is black, pointed, and curved slightly upwards towards the tip. It is long, surpassing twice the length of the avocet's small, rounded head. Like many waders, the avocet has long, slender legs and slightly webbed feet.[10] The legs are a pastel grey-blue, giving it its colloquial name, blue shanks. The plumage is black and white on the back, with white on the underbelly. During the breeding season, the plumage is brassy orange on the head and neck, continuing somewhat down to the breast. After the breeding season, these bright feathers are swapped out for white and grey ones.[11] The avocet commonly preens its feathers - this is considered to be a comfort movement.[12]
The call has been described as both a shrill and melodic alarm bweet, which rises in inflection over time.[10][11][13] Avocets use three distinct calls: common call, excited call, and broken wing call.[14] The common call is a loud repeated wheep. The excited call has a similar wheep sound, but it speeds up rather than having an even rhythm. Lastly, the broken wing call is noticeably different from the other two calls. It is a distressed screech sound and is alarming rather than melodic.[14]
American avocets were previously found across most of the United States until extirpated from the East Coast. The breeding habitat consists of marshes, beaches, prairie ponds, and shallow lakes in the mid-west, as far north as southern Canada.[8] These breeding grounds are largely in areas just east of the rocky mountains including parts of Alberta, Saskatchewan, Montana, Idaho, Washington, Utah, North and South Dakota, Nebraska, Colorado, and even down to parts of New Mexico, Oklahoma and Texas.[11] Their migration route lands them in almost every state in the western United States. The avocet's wintering grounds are mainly coastal. Along the Atlantic Ocean, they are found in North and South Carolina, Georgia and Florida. There are also wintering grounds along the Gulf of Mexico in Florida, Texas, and Mexico, and along the Pacific Ocean in California and Mexico. There are resident populations in the Mexican States of Zacatecas, San Luis Potosí, Guanajuato, Hidalgo, Mexico City and Puebla, and in Central California.[11]
Flocks ranging from 50 to 300 avocets migrate together to their breeding sites together during peak season, which is typically in the spring.[15]
The American avocet breeds in anything from freshwater to hypersaline wetlands in the western and mid-west United States.[11][16] After reaching their breeding grounds, the avocets quickly establish territory in pairs.[15] Throughout the breeding season, these pairs engage in a series of copulatory displays, which is initiated by either sex and often involves preening.[11][15] After breeding, the birds gather in large flocks, sometimes amounting to hundreds of birds. Nesting takes place near water, often alongside black-necked stilts, usually on small islands or mucky shorelines. The avocets nest on the ground in places with little to no surrounding vegetation. They make shallow indentations in the ground for their nest and line it with grass, feathers, pebbles or other small objects. Some avocets do not line their nests at all.[8] During the breeding season, avocets lay around 3–5 eggs, with 4 being the most common number.[14] One case study of the 1968 and 1969 breeding seasons suggests that this number allows for the highest rate of hatching success.[15] They incubate them over a period of 23–25 days. Both parents are involved in the incubation process, taking turns during the day (except at night, where only the female incubates the eggs).[15][14] Both parents take care of the newborn American avocets after they hatch. Male parents are more present in incubation during the first 8 days, whereas female parents dominate incubation throughout the remaining 16 days.[17] Time spent caring for newborn chicks equates to that spent incubating. Since newborns are able to walk, they are capable of feeding themselves and do not require extensive care from their parents.[14][17] The young are expected to begin flying 4 to 5 weeks after hatching.[15]
Each pair defends their own territory against predators and other avocets. Nests are built in areas that predators would struggle to gain access to. Predators that do try to approach the colony find themselves surrounded by several adult avocets running around, trying to distract them. While incubating however, the avocets tend only to their nest and defense is considered a lower priority, unless the eggs are in immediate danger, in which case the avocets may take more aggressive measures, calling loudly and flying at the threat.[15][14]
The American avocet tends to prefer habitats with fine sediments for foraging.[18] In the winter, it feeds extensively on brine shrimp. Usually, this entails the avocet pecking while walking or wading on the shore, but it can also swim to expand foraging area. During the breeding season, avocets continue to eat brine shrimp but switch mainly to consuming brine flies. Brine flies and brine fly larvae are so abundant in avocet breeding grounds that they often blacken the surface of any exposed mud. Brine flies sustain the avocet during its breeding season.[12] The avocet employs both visual and tactile methods of feeding.[11] The primary visual feeding method is pecking at flies. However the avocet will also feed by plunging (wherein the head and neck of the bird are submerged), snatching (wherein the bird catches a flying insect), and bill pursuit (wherein the bird repeatedly opens and closes its bill while moving its head along the surface of the water). Methods of tactile feeding include filtering, scraping, and scythe feeding.[12]
Shooting and trapping of American avocets led to population decline until the 1900s. During this time, the species was extirpated from most of the East Coast of the United States.[11] By 1918, Avocets became protected under the Migratory Bird Treaty Act (16 U.S.C. 703-712). Since that time, other threats have emerged. Contaminants and toxins such as DDT, selenium, and methylmercury, have increased in American Avocet habitats in recent years. Although the effects are highly contested, these increased concentrations have potential negative effects on American avocet breeding success, especially because Avocet chicks are more susceptible to environmental disruptions than adults.[11][16] The avocet also faces habitat loss. While agricultural and industrial environments have become alternate habitat for the avocet, natural wetlands are decreasing rapidly.[11] Additionally, increases in the salinity levels of wetlands have had adverse effects on the breeding and development of avocets. Young avocets in saline or hypersaline environments often combat weight loss and dehydration.[16] Although American avocets face numerous environmental challenges, numbers have stayed steady, and according to the National Audubon Society, numbers have been increasing steadily in the eastern United States for the past few years.[14] The American avocet is protected under the Migratory Bird Treaty Act of 1918.[19]
In his famous The Birds of America, John James Audubon describes a day of stalking and spying on the avocet. He judiciously noted their foraging, nesting, defensive, and flight behaviors.[10]
Winter plumage
Nesting
Adult with a chick at Palo Alto Baylands Nature Preserve, California
Breeding plumage
Quintana, Texas. Winter
In flight at the Sacramento National Wildlife Refuge, California
American avocet adult with chicks, Great Sand Dunes National Park The American avocet (Recurvirostra americana) is a large wader in the avocet and stilt family, Recurvirostridae, that is found in North America. It spends much of its time foraging in shallow water or on mud flats, often sweeping its bill from side to side in water as it seeks its crustacean and insect prey.
