ABSTRACT
The ring-billed gull lives primarily in temperate North America, breeding from Colorado and California northwestward into British Columbia east to Quebec. This population has grown explosively since 1930 throughout its range and it has become a serious pest to some other species of gulls or terns. Ring-billed gulls commence breeding at 2 or 3 years old. Nest density is quite variable from a low of 2766 nests per hectare up to 12,770 nests per hectare in whole colonies, and density in small areas may exceed 20,000 nests per hectare. Accuracy is a problem when shrubs or heavy herbaceous vegetation is present. Also, it is often difficult to distinguish incubators from nonincubators of other species or loafing gulls, especially in rough terrain or on colony edges. It does not have the accuracy of the quadrat or nest count method; compared to actual counts in colonies, the accuracy of this method is limited to about 11 to 14%.
