Shorebird trends on Bolinas Lagoon
Shorebirds include small to large-sized waterbirds with varying bill, leg, and toe lengths. They are adapted to the type of food they eat as well as the areas they forage in. Most species peck or probe for invertebrates in Bolinas lagoon's extensive mudflats. Some species forage in the salt marsh at high tide. Pastures and tilled land near the lagoon are also used by some species at high tide during periods of wet weather.
For shorebird graphs and profiles click a link below:
(Click here to download the Shorebird Trends Packet) - check back soon
Black-bellied Plover
Snowy Plover
Killdeer
American Avocet
Greater Yellowlegs
Whimbrel
Long-billed Curlew
Marbled Godwit
Willet
Black Turnstone
Sanderling
Dunlin
Western Sandpiper
Least Sandpiper
Common Snipe
About Graphs
References
For other waterbird trend pages click a link below:
Diving Duck trends
Dabbling Duck trends
Grebe trends
Cormorant trends
Heron & Egret trends
Tern trends
Other Waterbird trends
Black-bellied Plover
Pluvialis squatarola
Description
Breeding males have a striking black belly which contrasts with a mottled white and black back.
Range
The Black-bellied Plover breeds in the high Arctic of North America and Eurasia. It winters along the east and west coasts of the United States, as well as in Mexico, the West Indies, and Central and South America, including the coasts of Chile and Argentina.
Diet
The Black-bellied Plover loves to eat invertebrates, such as marine invertebrates and crustaceans, while foraging over sandy and muddy flats at a receding tide. This species also commonly forages at night, using its large eyes to search for a variety of foods. On their wintering grounds, Black-bellied Plovers have been observed to aggressively defend feeding territories.
Natural History Notes
The Black-bellied Plover is especially shy and wary of disturbances. In mixed flocks, other birds seem to rely on the plover to give an early alarm call if danger is near. Fairly common in the summer and very common in the winter, this Point Reyes resident arrives in the fall from mid-July through October. The Black-bellied Plover requires exposed tidal flats for foraging. At Bolinas, this species prefers intermediate substrate texture rather than sandy or muddy areas. Also look for the plover on sandy beaches, flat rocky shores, and rain-soaked pastures.
Bolinas Lagoon Population Trends
The Black-bellied Plover population has peaked twice in the past 35 years on Bolinas Lagoon. In 1980, the population peaked at 300 birds. After a drop to 120 in 1985, the population rebounded to 400 in 1995. Over the past ten years, the population has been decreasing. In 2005, there were about 260 Black-bellied Plovers on the lagoon.
Snowy Plover
Charadrius alexandrinus
Description
A small plover, with an incomplete breast band, visible as dark side patches. Snowy Plovers have pale brown upperparts, dark gray to blackish legs, and a slender black bill. They develop a dark forehead patch, and their existing cheek patches and breast markings become darker for breeding.
Range
Lives year-round along the Pacific Coast from Washington to Mexico, and along the Gulf Coast from Mexico to the Florida Panhandle. Breeds locally inland from California, Oregon, and Nevada east to Oklahoma and Texas.
Diet
Their main foods include terrestrial and aquatic invertebrates.
Natural History Notes
Residing on large, flat sandy beaches, well-camouflaged Snowy Plovers are found in a habitat where few other birds live. Despite this species’ persistence in breeding, its numbers are small. Less than 20,000 individuals inhabit the United States. Along the U.S. Pacific and Gulf coasts, the population is restricted because of habitat degradation and expanding recreational use of beaches.
Bolinas Lagoon Population Trends
After peaking at about 25 wintering birds in the alte 1970s, numbers declined sharply until the species became absent in the late 1990s. Wintering Snowy Plovers are beginning to return to Bolinas Lagoon. Breeding plovers haven't been encounted at the Lagoon since the 1980s.
Killdeer
Charadrius vociferous
Description
The largest Northern American “ringed” plover, The Killdeer is widespread and conspicuous. Killdeers can be distinguished by a brown back and white belly, with two black bands across the breast. In flight, their rusty rump and tail feathers are visible.
Range
Killdeers breed throughout much of North America, from eastern Alaska across Canada to Mexico and the Caribbean. Winters in most of the United States, south to Central America and northwestern South America.
Diet
The Killdeer’s main food sources include terrestrial invertebrates, especially earthworms, grasshoppers, beetles, and snails; infrequently feeds on small vertebrates and seeds.
Natural History Notes
The Killdeer is the most widespread and well known of North American plovers because of the variety of areas it frequents, its tolerance of humans, and its recognizable “killdeer” vocalizations.
Killdeers are also well known for their distraction displays. If a nesting Killdeer is approached by a predator, it will perform a distraction display, dragging its wing to give the elusion that it’s broken. This display is usually effective in luring the predator away from the eggs or young, at which point the bird then "recovers" and flies off.
Bolinas Lagoon Popluation Trends
The decline in winter numbers at Bolinas Lagoon likely reflect changing agricultural practices and especially the disappearance of heavily grazed pastures used by Killdeer in the Pine Gulch Creek delta.
American Avocet
Recurvirostra americana
Description
The striking American Avocet has long bluish legs and white and black upperparts. During the breeding season the head and neck become rusty colored. American Avocets have a long, recurved bill, which is smaller and more upturned in females.
Range
American Avocets breed along the Pacific coast from San Francisco Bay to Baja California and in wetlands in arid areas of the western United States, including the Great Salt Lake, the Tulare Basin of California, and the northern Great Basin. Avocets winter in coastal wetlands of California..
Diet
Eats mostly crustaceans, insects, aquatic vegetation, and seeds. Forages by sweeping bill back and forth beneath the water’s surface, finding food both visually and tactually. The sensitive bill has a high number of tactile receptors, allowing avocets to feel food in the mud.
Natural History Notes
The American Avocet is common throughout the winter on Bolinas Lagoon, but rare throughout the rest of the year. Fall migration extends from July through November and spring migration is from March through May. In Point Reyes, avocets can be found on Bolinas Lagoon and at Bodega Harbor. Birds at Bolinas Lagoon are suspected to roost nightly in San Francisco Bay and spend days foraging at Bolinas. Avocets prefer to feed on mudflats in estuaries and lagoons.
Bolinas Lagoon Population Trends
The number of American Avocets present on Bolinas Lagoon from December through February has increased from under 50 birds in 1971 to about 450 birds in 2005.
Greater Yellowlegs
Tringa melanoleuca
Description
A slender, gray and white wader with a conspicuous white rump and long yellow legs. Greater Yellowlegs are medium to large shorebirds with pale spotted, dark gray backs, pale bellies and a slightly upturned bill. Lesser Yellowlegs is similar but smaller, with a shorter, straighter, and more slender bill and a different call.
Range
Breeds from south-central Alaska eastward across Canada. Winters from the southern United States south to South America.
Diet
Main diet consists of small invertebrates, small fish and frogs. Generally feeds pecking or skimming prey from the water.
Natural History Notes
Greater Yellowlegs are noisy and conspicuous birds. More solitary than most shorebirds, it is rarely seen in large numbers, although small flocks form during migration.
Bolinas Lagoon Population Trends
The small winter popluation at Bolinas Lagoon has exhibited two peaks since 1971 and currently consists of about 12 birds.
Whimbrel
Numenius phaeopus
Description
A medium-sized curlew with a long decurved bill and a large body. Whimbrels are gray-brown above, with bold head stripes and long legs. Females are slightly larger than males.
Range
Breeds along the coasts of Alaska and northern Canada. Also breeds in northern Europe and Russia. Winters on both coasts of the United States, from northern California and North Carolina southward, and along coasts and offshore islands from Mexico to Chile and Brazil.
Diet
Whimbrels diet includes mostly marine invertebrates like crabs. Whimbrels use their perfectly adapted long decurved bills to pull their favorite winter food (crabs) out of burrows.
Natural History Notes
The Whimbrel is the most wide-ranging of the curlew species and the only one that nests across both the Neartic and Paleartic. Some migrating Whimbrels make a nonstop flight of 4,000 km (2,500 miles) from southern Canada or New England to South America.
Bolinas Lagoon Popluations Trends
Since 1975 when the species only occurred irregularly in winter on Bolinas Lagoon, the population has increased to about 24 birds.
Long-billed Curlew
Numenius americanus
Description
The Long-billed Curlew, the largest shorebird, is recognizable by its long, downward curving bill. The Latin name "Numenius," meaning "of the new moon" describes the half crescent shape of the bird’s long bill. The Long-billed Curlew’s brown mottled plumage helps it become easily camouflaged in prairie fields where it nests.
Range
This curlew breeds in the northern prairie states, parts of Washington, Nevada, California, and south central Canada. After breeding, curlews migrate to their wintering grounds, which extend along the coast of California to Baja California and throughout Mexico and parts of Central America.
Diet
The Long-billed Curlew uses its long beak to probe for benthic invertebrates and crustaceans, such as shrimp and crabs, living deep in the mud. They also eat insects and small vertebrates. At Bolinas Lagoon, ghost shrimp and crabs are major prey.
Natural History Notes
In California, the Long-billed Curlew is dependent on the Central Valley, Imperial Valley, coastal wetlands for wintering grounds.In Point Reyes, the Long-billed Curlew is fairly common throughout the winter and very rare in the summer. Curlews migrate through California during the fall from mid-June to October and in the spring from late March to early May. During the winter, look for the only regular winter population of curlews at Bolinas Lagoon. Throughout Point Reyes, curlews feed primarily on tidal flats and occasionally in salt marshes.
Bolinas Lagoon Population Trends
The number of Long-billed Curlews on Bolinas Lagoon have increased from about 35 birds in 1970 to about 270 birds in 2005.
Marbled Godwit
Limosa fedoa
Description
This crow-sized shorebird has a two-toned pink and black upturned bill, dark, mottled upperparts and buffy cinnamon colored underparts. Its song is a loud “Kerrick” or “God-wit.”
Range
Marbled Godwits have three distinct breeding grounds, which include the grasslands of the northern Great Plains of the United States and southern Canada; the Alaskan Peninsula; and James Bay in Ontario, Canada. During the winter, Marbled Godwits live along the coast of northern California, southeast United States, Mexico, and South America.
Diet
Godwits can be seen with their heads submerged in shallow water as they feed on crustaceans, clams, snails, and worms in the mud. At Bolinas Lagoon, marine worms are their primary prey.
Natural History Notes
This common winter and summer resident can be found feeding on tidal flats and on sandy beaches in the Bolinas and Point Reyes area. Marbled Godwits are seen frequently feeding at the Bolinas Lagoon during the day and then seen flying south at dusk, most likely to San Francisco, to roost for the night.
Bolinas Lagoon Population Trends
The Marbled Godwit population on Bolinas Lagoon has increased from about 100 birds in 1971 to about 900 birds in 2005.
Willet
Catoptrophorus semipalmatus
Description
The Willet is easily recognized in flight by the broad, white white bands on blackish wings. Otherwise, this medium-sized grey and white shorebird has no distinct field markings in winter. Listen for its loud, ringing “pill-will-willet.”
Range
The Willet has one of the largest latitudinal breeding ranges of temperate breeding shorebirds in North America. Willets in North America can be separated into two distinct breeding populations, the Eastern Willet and the Western Willet. The subspecies have separate breeding and wintering grounds. After breeding in the Great Plains and Great Basin of western United States, Western Willets migrate south for the winter. Their wintering grounds extend from the coast near Humboldt Bay in Northern California to Peru.
Diet
This species feeds during the day and night, eating clams, snails, crabs, amphipods, aquatic insects, and worms. Willets use a variety of foraging methods, but primarily peck for prey in the mud.
Natural History Notes
Willets are commonly seen in Point Reyes as summer and winter residents, with numbers peaking in the fall as migrating transients stop over in California. Willets migrate through California from mid-July through early November. Look for Willets feeding on sandy and muddy substrates of tidal flats, sandy and rocky beaches, and along the edges of lagoons. As opposed to most shorebirds, Willets regularly feed in salt marshes.
Bolinas Lagoon Population Trends
The Willet population has remained relatively stable, at 300 - 400 birds since 1970, except for a peak of over 600 birds in 1993. In 2005, there were about 450 Willets on Bolinas Lagoon.
Black Turnstone
Arenaria melanocephala
Description
A small-sized shorebird, the Black Turnstone is a conglomerate of black and white. It has a white spot between the eye and bill, short orange legs, and a distinctive black and white wing pattern visible during flight.
Range
The Black Turnstone’s range is limited to western North America. Its breeding grounds are along the coast of Alaska and its wintering grounds along the west coast, from southeast Alaska to Baja, Mexico.
Diet
Like its name suggests, this bird forages by flipping over objects to access the crustaceans and other intertidal organisms underneath. Its bill is adapted to prying apart mussels and barnacles.
Natural History Facts
In Point Reyes, the Black Turnstone is rare in the summer, but a common spring and fall migrant, and winter resident. They can be seen foraging on rocky reefs on the outer coast, estuarine tidal flats, and at times in kelp on sandy beaches.
Bolinas Lagoon Population Trends
The number of Black Turnstones on Bolinas Lagoon has fluctuated widely in the past thirty years. The population peaked at around 100 birds in 1973, then dropped to about 20 birds in 1975. Over the past ten years, the number of turnstones peaked at 70 birds but has recently decreased. In 2005, there were 25 Black Turnstones.
Sanderling
Calidris alba
Description
This is a small, plump sandpiper with a stout black bill, black legs and feet, and a conspicuous white wing stripe. Summer adults have a rufous head and breast, and a white belly. By winter, rufous areas have been replaced by pale gray, and birds look almost white and paler than any other shorebird. Note dark shoulder, and dark leading edge of the wing on Sanderlings in flight.
Range
Breeds in the high Arctic tundra from Alaska eastward to Baffin Island. Winters along both coasts from Canada to southern South America.
Diet
The Sanderling eats aquatic and terrestrial invertebrates. On coastal marine beaches, they feed on small crustaceans, mollusks, small polychaete worms, and insects.
Natural History Notes
Sanderlings have one of the most extensive winter ranges of all shorebirds in the world. They can be found worldwide on almost every sandy, coastal beach during the winter.
Sanderlings can easily be identified by their foraging behavior. They commonly are seen in flocks “chasing” waves. As the water moves away from the beach, they run back to retrieve invertebrates exposed by the retreating waters.
Bolinas Lagoon Population Trends
The winter population has fluctuated from a low of 25 to about 180 birds during the past 35 years.
Dunlin
Calidris alpina
Description
This small sandpiper is recognizable by its black belly and bright rufous back during the breeding season. During the winter, Dunlins are gray and white with a drooping black bill and black legs. Dunlins typically occur in flocks of one thousand to tens of thousands of birds.
Range
Dunlins breed in northern Alaska and Canada. After breeding, Dunlins migrate to wetlands along the Pacific and Atlantic coasts of the United States and Mexico. A substantial number of Dunlins move to the Central Valley of California during mid-winter.
Diet
In the winter, Dunlins eat mollusks, crustaceans, and marine worms. On the tundra, Dunlins eat insects, spiders, worms, mollusks, and seeds.
Natural History Facts
In Point Reyes, the Dunlin is commonly seen late in the fall as it stops over during its migration south. A substantial number winter in Point Reyes. Dunlins are rare in the summer. They feed on estuarine tidal flats, margins of lagoons, freshwater ponds and sewage ponds, and occasionally on rocky reefs.
Population Trends on Bolinas Lagoon
The number of Dunlins has fluctuated widely in the past thirty-five years. The population first peaked at over 4000 birds in 1976, then dropped to about 1250 birds in 1983. In 1993, the population peaked again at around 4000 Dunlins and has steadily decreased to only about 400 birds in 2004.
Western Sandpiper
Calidris mauri
Description
This small sandpiper is slightly larger than the Least Sandpiper, with a noticeably larger, thicker bill that droops slightly at the tip. Its black legs contrast with pale gray plumage in the winter. During the breeding season, it has a very streaky breast and rusty colored scapulars and crown. While flying, the Western Sandpiper can be characterized by extremely rapid wing beats and zigzag flight.
Range
During the winter, the Western Sandpiper is commonly found along the east and west coasts of the southern United States, and Latin America to northern South America. Its breeding grounds are restricted to a small area in Alaska where it breed in dense colonies. Up to 6,500,000 individuals have been estimated passing through the Copper River Delta in Alaska during spring migration, a site where 90% of the population stops to feed before reaching the breeding grounds.
Diet
At their wintering grounds, Western Sandpipers forage by pecking or probing for marine benthic invertebrates, including amphipods, polychaete worms, and bivalve mollusks, from the surface of a mud flat.
Natural History Notes
In addition to being a winter resident, the Western Sandpiper can also be found at Bolinas Lagoon during migration periods from early July to October and in the spring from March to mid-May, when there is a noticeable peak in the sandpiper population. The majority of wintering sandpipers at Bolinas Lagoon and Limantour Estero are males as the females tend to travel further south for the winter. At Bolinas, Western Sandpipers prefer sandier areas than Least Sandpipers.
Bolinas Lagoon Population Trends
Only small numbers of Western Sandpipers winter on Bolinas Lagoon. Except for a peak of about 250 birds in 1992, fewer than 100 birds occur during winter. There has been a large decrease in the number of Western Sandpipers on the lagoon during spring migration, from 35,000 birds in 1972 to fewer than a few hundred in 2005.
Least Sandpiper
Calidris minutilla
Description
The smallest shorebird, the Least Sandpiper can be distinguished from most other sandpiper species by its small size, shorter bill, and short yellowish legs. In flight, it is darker and has quicker wingbeats than the Western Sandpiper. A breeding Least Sandpiper has a rufous back with black spots and two thin white lines that run down its back.
Range
This sandpiper breeds in the subarctic tundra and far northern Boreal forests in Alaska and northern Canada. During migration, Least Sandpipers will fly nonstop for over 3000 to 4000 km from new England to wintering grounds in South America. Wintering grounds extend from coastal California to Mexico, Central America, and northern South America.
Diet
The Least Sandpiper probes and pecks in damp mud for benthic invertebrates, such as amphipods and worms. It also preys on insects.
Natural History Notes
The Least Sandpiper is an abundant fall transient and a very common winter resident in Point Reyes. Spring migration is from March until mid-May and fall migration begins as early as July. Least Sandpipers forage mostly on tidal flats, where they prefer muddier areas than Western Sandpipers. They also feed in salt marshes, on the margins of freshwater ponds, in wet pastures, and occasionally on sand beaches and flat rocky areas.
Bolinas Lagoon Population Trends
The number of Least Sandpipers found in the winter has fluctuated during the past thirty years. The population peaked at nearly 2000 birds in 1993 and has been decreasing since. In 2004, there were about 700 birds.
Common Snipe
Gallinago gallinago
Description
the Common Snipe is a brownish shorebird with an extremely long beak. Snipe's are particularly well camouflaged with a striped head and back, white belly, and rusty tail. They are usually only seen when flushed from the edge of a marsh or a pond. In flight they are fast and erratic.
Range
Breeds from northern Alaska and Canada south to the southwestern and northeastern United States. Winters throughout much of the United States, all of Central America, the Caribbean, and northern South America.
Diet
Eats mostly larval insects, but also takes crustaceans, earthworms, mollusks, some vegetation and seeds. Feeds both on land and in shallow water, but usually in or near cover.
Natural History Notes
Common Snipe have an extremely long and flexible bill. The tip of it can be opened and closed independent of the base of the bill. Like other shorebirds, it has especially sensitive openings or “sensory pits” at the end of the bill that it uses to probe deeply in the mud to feel for prey.
They are known for making a whistling sound in flight. The outer tail feathers are curved and thin which create the noise when wind rushes by them.
Bolinas Lagoon Population Trends
The population declined sharply at Bolinas Lagoon after cattle were removed from adjoining marshy pastures which subsequently became covered with tall vegetation or were converted to row crops.
