Distribution Map - Ring-billed Gull (Larus delawarensis)

GAP Analysis Predicted Distribution Map

Ring-billed Gull (Larus delawarensis)

Species Code: LADE

Breeding Range Map
The green area shows the predicted habitats for breeding only.
© NatureMapping Program

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Predicted breeding range

= Core Habitat
= Marginal Habitat

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Breeding Range Map
The green area shows the predicted habitats for breeding only. The habitats were identified using 1991 satellite imagery, Breeding Bird Atlas (BBA), other datasets and experts throughout the state, as part of the Washington Gap Analysis Project. Habitats used during non-breeding months and migratory rest-stops were not mapped.

Observations | Historic Gap points

Metadata (Data about data or how the map was made)

Habitat

This species is common in eastern Washington, breeding colonially on gravel islands in lakes and rivers and feeding in agricultural lands, cities, and wetlands nearby. They are locally common breeders in western Washington on dredge-spoil islands in Grays Harbor and Willapa Bay.

The core areas of use were Sitka Spruce, Ponderosa Pine, Oak, and steppe zones. In the Sitka Spruce zone, developed areas, agriculture, wetlands, coastal habitats, and open areas were good. In the east side zones, fresh water/wetlands, development, and agriculture were good. However, although east-side breeding colonies themselves are restricted to wetlands, this species feeds in the other modeled habitats. Everywhere, its range was limited to the vicinity of known breeding colonies.

Many of the BBA records recorded by observers as "possible" breeders are actually from non-breeding birds seen throughout the breeding season. The first known colonies for western Washington were reported in 1976 from Ellen Sands in Willapa Bay and Whitcomb Island in Grays Harbor. Migrants occur at fairly high elevations throughout the Cascades. Single nesting attempts are noted from locations throughout the Puget Trough, but these generally do not constitute colonies and are likely to be fleeting. Birds in agricultural areas are primarily foraging on small rodents. The Ring-billed Gull is ecologically similar to the California Gull, though more widely distributed in Washington. Numbers of breeding birds typically fluctuate from year to year, though they have increased overall in the past 50 years due to dam projects in eastern Washington. At Sprague Lake it was found that reproductive success was highest in birds nesting in tall grass sites, and lowest on bare ground sites. It has also been found that in mixed island colonies of Ring-billed and California Gulls, Ring-billed Gulls are forced to use the lower habitats near the water, and were more likely to suffer nest loss resulting from water level fluctuation. The Crescent Island colony numbered 1500 birds in 1996, contributing to a total of about 7000 breeding pairs in the southern Columbia Basin. In Washington, Breeding Bird Survey data show a significant increase of 7.0% per year from 1966 to 1991.

Translated from the Washington Gap Analysis Bird Volume by Uchenna Bright
Text edited by Gussie Litwer
Webpage designed by Dave Lester