The American avocet (Recurvirostra americana) is a large shorebird belonging to the avocet and stilt family, Recurvirostridae. Avocets are elegant birds with long, thin, upcurved bills and long, slender legs. Their most distinctive feature is their unique recurved bill, which enables them to sweep their heads from side to side through shallow water to catch tiny crustaceans and insects.
American avocets breed primarily in the Prairie Pothole Region of central North America. They nest on islands in shallow lakes and wetlands from southern Alberta through Montana and the Dakotas. After breeding, American avocets migrate in flocks to coastal estuaries and wetlands from Washington to Mexico for the winter. Avocets are highly social and gather in large flocks when not breeding.
Description
American avocets are medium-sized shorebirds reaching lengths of 15 to 20 inches with wingspans of about 30 inches. They weigh between 12 to 16 ounces on average.
Avocets have long bluish-gray legs and a long, thin, upturned bill that is black towards the tip. Their heads and necks are cinnamon-colored in breeding plumage and pale gray in winter. Breeding birds have black and white striped wings and backs, white underwings, and a black-and-white barred tail. In winter, the black stripes on the back and wings fade to gray. The avocet’s plumage is cryptic, helping it blend into its surroundings.
Male and female American avocets look identical. Juvenile birds resemble winter adults but have buffy wash on the neck and breast. Avocets molt their body feathers twice a year after breeding and before spring migration. Their flight feathers molt once a year after breeding.
Range and Habitat
The American avocet has a widespread breeding distribution across the prairie pothole regions of central North America. Their breeding range covers southern Alberta and Saskatchewan through Montana, North Dakota, South Dakota, Minnesota, and extending into Nebraska, Colorado, and New Mexico. Isolated breeding populations occur locally in Oregon, California, Nevada, Utah, Wyoming, Oklahoma, and Texas.
Avocets nest colonially on open shorelines of shallow freshwater lakes, alkali wetlands, marshes, and ponds. They prefer sites with small islands for nesting. Avocets often share nesting sites with other wading birds like stilts, phalaropes, and terns. Ideal breeding habitat has water depths between 4-8 inches deep with muddy bottoms rich in small invertebrates.
After breeding, avocets migrate in flocks to coastal estuaries, beaches, marshes, deltas, and wetlands. Their winter range extends along the Pacific Coast from Washington to Mexico and along the Gulf Coast from Florida to Mexico. Some birds remain year-round in parts of California, Texas, and Louisiana.
Diet
The diet of American avocets consists predominantly of small aquatic invertebrates, mainly insects and crustaceans. They feed by sweeping their upturned bills from side-to-side just below the water’s surface to catch prey items by touch. Avocets also pick prey from mud or vegetation.
Common prey includes insects like beetles, flies, mosquitoes, dragonflies, grasshoppers, and caterpillars. They also eat small crustaceans including brine shrimp, fairy shrimp, water fleas, and small snails. On the wintering grounds, avocets feed more on marine invertebrates like marine worms, shrimp, crab larvae, and tiny clams.
Avocets may occasionally eat seeds or plant material, but animal prey makes up over 90% of their diet. They forage mainly in shallow water or saturated mud, probing and sweeping with rapid head movements. Avocets may also forage on dry land, picking insects and spiders from the vegetation or surface.
Breeding
American avocets breed from April through August, depending on their range. They arrive on the breeding grounds already paired from the previous year. Avocets show a high mate and site fidelity, returning to the same nesting site and partner annually. However, if a mate is lost over the winter, the remaining bird will find a new partner quickly.
Avocets nest in loose colonies that can range from just a few to over 100 breeding pairs. They prefer nesting islands that provide some protection from land predators. Nests consist of a shallow scrape in the ground lined with vegetation, gravel, and shells. The female lays 3-4 brown or olive-colored eggs that are carefully incubated by both parents for 22-28 days.
The precocial chicks hatch covered in downy feathers and can leave the nest within a day. The parents lead the chicks to feeding areas where the young feed themselves. To avoid predation, parents may move the chicks frequently between wetlands. Fledging occurs around 4-5 weeks, and the young remain with their parents until they migrate in late summer. Most avocets first breed when they are 2-3 years old.
Behavior
American avocets are highly social birds that reside in flocks outside of breeding season. During winter and migration, they congregate in large groups numbering in the hundreds or even thousands of birds. Their long legs allow them to wade into deeper water than many shorebirds to probe the mud for food. Avocets often feed together in shallow waters by swinging their upturned bills from side to side to catch prey stirred up by the group.
Avocets engage in elaborate courtship displays including twirling flights with the wings held in a sharp V-shape. Males perform elaborate dances, running through shallow water quickly with the head erect to attract females. After pairing, avocet pairs perform duets, loudly calling and repeating their display.
To defend their nesting territories, avocets become very aggressive, charging at intruders with their bill pointed downwards like a sword. Their black and white wings and tail are raised to appear more intimidating during these threat displays. Avocets may also engage in physical combat with other intruding avocets to defend their nest site.
Migration
American avocets undergo long migrations twice annually between their breeding and wintering areas. After breeding, they leave the prairie potholes from July to October. They migrate in flocks to wintering sites along the Atlantic, Pacific, and Gulf Coasts. Spring migration back to the breeding grounds occurs from mid-March through May.
Avocets migrating long distances fly mainly at night. Some populations shorten their migration distances by stopping at inland sites with suitable wetland habitat. Young avocets tend to winter further south than adult birds. Their migrations cover thousands of miles between the Central Plains and West Coast wintering sites. Tracking studies show the fastest migrations occur along narrow corridors across the Great Plains.
Conservation Status
According to the IUCN Red List, the American avocet is classified as a species of Least Concern. It has a large range and a population estimated between 350,000 to 400,000 individuals. Avocet numbers declined in the late 19th and early 20th centuries due to hunting and the plume trade. However, protection measures allowed populations to rebound to stable levels.
Current threats include habitat loss on the breeding grounds due to wetland drainage and degradation. Pollution, agricultural runoff, and water extraction also impact breeding sites. Avocets are still hunted for sport and food in some areas despite protections. Conservation efforts focus on preserving prairie wetland habitat and mitigating threats during migration.
Population Trends
After major declines in the late 1800s, avocet populations rebounded in the 20th century following hunting restrictions. The first comprehensive survey in 1955 estimated around 77,000 individuals. Counts increased to around 105,000 birds in the 1970s.
Numbers fluctuated between 100,000 to 200,000 through the 1980s and 1990s as habitat conditions changed. The most recent survey in 2014 tallied over 136,000 American avocets across their range. While still below historical levels before market hunting, populations appear stable in recent decades.
Major Threats
– Habitat loss and degradation of prairie wetlands
– Pollution and agricultural runoff diminishing water quality
– Climate change impacting breeding sites
– Human disturbance at nesting colonies
– Hunting and poaching on wintering grounds
Unique Adaptations
American avocets have several unique physical and behavioral adaptations that allow them to thrive in their wetland habitat:
– Specialized upturned bill ideal for sweeping through shallow water to catch prey
– Long blue legs allow wading into deeper water than other shorebirds
– Cryptic black and white plumage provides camouflage in open nesting sites
– Webbed feet provide surface area to walk on soft mud
– Precocial young feed themselves soon after hatching
– Aggressive territorial displays using wings and bill defend nest sites
– Gregarious flocking behavior facilitates feeding and migration
Role in the Ecosystem
As a abundant wetland bird, the American avocet fills an important niche in prairie and coastal ecosystems. Some key roles include:
– Preying on insects like mosquitoes helps control pest populations
– Consuming crustaceans and mollusks recycles nutrients
– Nesting in colonies provides additional food sources to predators
– Stirring up sediments aerates water and releases nutrients
– Guano provides fertilizer to enrich water in breeding wetlands
– Serves as a sentinel species for wetland health and alterations
Key Facts
- Scientific Name: Recurvirostra americana
- Range: Breeds in prairie wetlands, winters along the Pacific, Atlantic, and Gulf Coasts
- Habitat: Shallow lakes, marshes, estuaries, salt flats
- Length: 15-20 in (38-51 cm)
- Wingspan: 30 in (76 cm)
- Weight: 12-16 oz (355-453 g)
- Lifespan: 10 years in wild
- Diet: Insects, crustaceans, mollusks
- IUCN Status: Least Concern
Frequently Asked Questions
What do American avocets eat?
American avocets are carnivores that eat small aquatic invertebrates like insects, crustaceans, and mollusks. They sweep their specialized upturned bills from side to side in shallow waters to catch prey.
Why do avocets have upside down bills?
The avocet’s distinctive upturned bill is an adaptation for feeding. By swinging it side to side underwater, the thin bill efficiently catches small creatures hidden in muddy waters. The slight upward curve may also help it grab and hold onto slippery prey.
How do avocets catch food?
Avocets feed by sweeping their bills back and forth through shallow water to catch prey by touch. The thin bill is sensitive enough to detect tiny insects, larvae, and crustaceans as it sweeps through. They may also pick prey directly off vegetation or the water’s surface.
How fast can an American avocet fly?
In sustained flight, American avocets fly around 20-30 mph. However, they are capable of short high-speed bursts up to 60 mph, especially during territorial displays or escape from predators. Their pointed wings and lightweight build are adapted for rapid, agile flight.
How far do American avocets migrate?
Migration distances vary across their range. Some fly over 2,500 miles between breeding sites in the northern plains to wintering grounds along the Gulf Coast. Birds in the west may migrate just a few hundred miles to coastal California and Mexico. Young avocets tend to migrate further south than adults.
How long do American avocets live?
The typical lifespan for an American avocet in the wild is around 10 years. The oldest known wild avocet was at least 22 years old. With such a long lifespan, avocets have multiple opportunities to breed and produce offspring.
Conclusion
The American avocet is a graceful shorebird distinguished by its specialized upturned bill, bold black and white plumage, and social nature. As a wetland species, it fills an important niche in prairie ecosystems by controlling insects, recycling nutrients, and serving as an indicator of habitat conditions. While avocet populations declined historically from hunting and habitat loss, improved protections have allowed numbers to rebound. Continued conservation efforts focused on preserving wetlands across their breeding range will help ensure the future of this unique bird. Understanding the avocet’s natural history and ecological roles highlights the importance of protecting the wetland habitats this species calls home.