California Gull Life History

Habitat

Habitat Lakes and PondsCalifornia Gulls primarily breed on sparsely vegetated islands and levees in inland lakes and rivers, but they also breed in salt ponds in the San Francisco Bay, California. Breeding colonies range from sea level to 9,000 feet elevation and are usually surrounded by water to prevent predators from reaching the nests. During the breeding season they may forage up to 40 miles away from the breeding colony in open areas including farm fields, garbage dumps, meadows, scrublands, yards, orchards, and pastures. They tend to avoid heavily forested areas. In the winter they forage along the Pacific Coast, using mudflats, rocky shorelines, beaches, estuaries, and river deltas. Back to top

Food

Food Aquatic invertebratesCalifornia Gulls are omnivores that eat Just about anything that will fit into their mouths, including fish, garbage, grasshoppers, mayflies, brine shrimp, earthworms, small mammals, cherries, bird eggs, grains, carrion, and more. They scavenge food from the ground, run after flying insects, pick prey off the surface of the water, and plunge into the water after fish. Back to top

Nesting

Nest Placement

Nest GroundPairs walk around their territory together digging small scrapes in the ground until they find a suitable spot to build a nest. They build their nest on the ground in the open or at the base of a small shrub. They nest in colonies, and sometimes they nest in the same spot as the previous year.

Nest Description

Both sexes help build the nest with small pieces of bone, feathers, grasses, and other pieces of vegetation found nearby. The female shapes the inside of the nest with her body to form a cup. It takes them about 1 week to complete the nest, which is around 11 inches wide. The size depends on how much material they add; some nests are just scrapes in the ground while others are larger with a lot of feathers and vegetation.

Nesting Facts
Clutch Size:1-4 eggs
Egg Length:2.5-2.7 in (6.3-6.8 cm)
Egg Width:1.7-1.9 in (4.4-4.7 cm)
Incubation Period:23-27 days
Nestling Period:3-4 days
Egg Description:Buff to greenish, with dark spots, speckles, splotches, and short swirls.
Condition at Hatching:Completely covered in down and able to stand within a few hours after hatching.
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Behavior

Behavior Ground ForagerAdept on land, in the air, and on the water, California Gulls run, fly, and swim to find food. On the breeding grounds, they often run through swarms of flies with their bills open. In the water they paddle much like a duck, but they also dive into the water after fish. They eat just about anything they can find, from grasshoppers to garbage. Resting gulls often stand on one leg or sit with their legs folded underneath with their eyes closed. They frequently associate with other California Gulls as well as other gull species. Despite their highly social nature, they defend their nest areas in the breeding colony. They threaten intruders by stretching their necks straight up, by pushing their heads forward and opening their bills, or by throwing their heads up and then down to their chest while calling. Gulls that share territorial boundaries sometimes bite grass or other vegetation, aggressively pulling at it to indicate ownership of the area. If a neighboring gull crosses the line, fighting and bill jabbing usually ensues. California Gulls form monogamous pairs when they are 4 years old, some of which stay together for more than one breeding season. When the pair is ready to mate, each bird tosses its head in an arc up and over the back and offers its mate food. They perform a choking display (see Sounds) before and during nest building, in which they put their breast to the ground and jerk their heads up and down as if they were choking. Back to top

Conservation

Conservation Low ConcernCalifornia Gulls are common throughout their range. They are also now breeding in large numbers in salt ponds in the San Francisco Bay area. According to the North American Breeding Bird Survey, populations were generally stable between 1966 and 2015, though there have been significant declines in some areas. Partners in Flight estimate a continental breeding population of 410,000 breeding birds. California Gull rates a 12 out of 20 on Partners in Flight's Continental Concern Score published in the 2016 State of North America's Birds report. The species is not on the 2016 State of North America's Birds' Watch List.Back to top

Credits

Dunne, Pete. 2006. Pete Dunne's essential field guide companion: Houghton Mifflin Harcourt.

Howell, S. N. G. and J. L. Dunn. 2007. A reference guide to gulls of the Americas. Boston: Houghton Mifflin Harcourt Company.

Karlson, Kevin and D Rosselet. 2015. Birding by Impression. Living Bird no. 25:34-42.

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl. 2002. Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, D.C.: Waterbird Conservation for the Americas.

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.

Sauer, J. R., D. K. Niven, J. E. Hines, Jr. Ziolkowski, D. J., K. L. Pardieck, J. E. Fallon and W. A. Link. The North American breeding bird survey, results and analysis 1966-2015 (Version 2.07.2017). USGS Patuxent Wildlife Research Center 2017.

Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

Winkler, David W. 1996. California Gull (Larus californicus), 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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