Author David Suddjian January 2000
Gulls are among the most common birds seen along our coast. Ten species can be found with relative ease in the Monterey Bay region during the course of a year. Others have been found only rarely. To learn to identify gulls you need to know: (1) what species to expect and when, (2) how to determine the age of a gull, (3) and what features to focus on for gulls of different ages. A wise approach in starting out is to focus study on the most common species (e.g., Western, Glaucous-winged, California and Ring-billed gulls), using them for comparison to less common species.
Depending on the species, gulls require 2-4(or 5) years to reach an adult-type plumage. The plumage and other features associated with each age are distinctive. Of our regularly-occurring species, a “2 year” gull is the Bonaparte’s Gull; “3 year” gulls include Heermann’s, Ring-billed and Mew; “4 year” gulls include California, Herring, Thayers, Western, Glaucous-winged and Glaucous. Note that some individuals, especially of the largest species, may require 5 years to fully attain adult features.
The following list of species provides some guidance about what species to expect and when to expect them. The flowcharts are a helpful resource that will assist in sorting out most individuals of the regularly occurring species (An earlier version of these flowcharts was obtained from Maryann Danielson, but I’m not sure of who first drew it up). However, successful use of the flowcharts first requires determination of the age of the bird. Some useful points to focus in aging gulls are given at the beginning of each flowchart. Distinctive species, such as Bonaparte’s, Heermann’s and Sabine’s gulls and Black-legged Kittiwake are not included in the flowcharts.
General Notes on the Occurrence of Gulls in the Monterey Bay Region
Regularly-Occurring Species
Bonaparte’s Gull – common late fall through spring. Large numbers of migrants evident during late fall and April to May, but only locally numerous in the winter. Small numbers linger through summer at a few sites along the immediate coast. Found offshore and along the coast (especially at creek and river mouths), and inland to lakes, wetlands, agricultural fields (especially in spring) and sewage ponds.
Heermann’s Gull – Common summer through early winter, uncommon late winter, rare to uncommon in spring. Found along the immediate coast and offshore. Pairs have nested at Robert’s Lake (Monterey Co.) and Año Nuevo (San Mateo Co.).
Mew Gull – Common late fall to early spring, rare to casual at other times (usually absent June to September). Found offshore, along the coast, and inland to lakes, agricultural fields and turf playing fields (especially during storms), and at landfills.
Ring-billed Gull – Fairly common from late summer through spring, rare and local during late spring and summer. Regularly found along the inner coast of Monterey Bay (Natural Bridges area to Monterey), but very rare along the outer coast from Monterey Peninsula south or along the northern Santa Cruz County coast. Found along the coast and inland to urban areas, schools, turf playing fields, lakes and landfills. Generally absent offshore.
California Gull – Very common, with lowest numbers from mid-spring to early summer. Found throughout the area, including offshore and along the coast, and inland to lakes, urban areas, schools, agricultural fields and turf playing fields and landfills. Most gulls seen flying in flocks high overland are this species.
Herring Gull – Uncommon to locally fairly common from late fall through early spring, rare to casual at other times (usually absent June to August). Found offshore and along the immediate coast (especially at river and creek mouths with large gulls flocks), inland less commonly to lakes and landfills.
Thayer’s Gull – rare to uncommon late fall through winter, very rare during spring, and casual to absent at other times. Found offshore and along the immediate coast (especially at river and creek mouths with large gulls flocks), inland rarely to lakes and landfills.
Western Gull – Very common, most abundant from late summer through mid-spring. Found offshore and throughout the coastal areas of the region, nesting at various locations along the coast. Frequents near-coastal urban areas and landfills, but rare at inland lakes. May be seen flying overland from the coast to the S.F. Bay.
Glaucous-winged Gull – Fairly common to common late fall to early spring, rare from mid-spring to mid-fall. Found offshore and along the coast, inland to landfills and rarely to lakes.
Note: hybrid Western x Glaucous-winged gulls are common from fall through winter in the areas occupied by these species. Hybrid Herring x Glaucous-winged gulls are also present.
Glaucous Gull – Very rare from late fall to early spring, with few acceptable late spring records. Normally absent mid-May to October. Found offshore and along the coast (especially at river and creek mouths), and inland to landfills. In late spring and summer beware of very pale 1st year Glaucous-winged Gulls, which are present in very low numbers.
Black-legged Kittiwake – Variably common to rare, with most present from late fall to early spring, and usually rare May to September. Found mostly offshore (and seen from boats), but sometimes found along the coast, especially following winter storms or high winds.
Sabine’s Gull – Uncommon late spring and early fall migrant. Usually only found offshore (and seen from boats). Very rarely seen close to shore or onshore.
Very Rare Species and Vagrants:
Laughing Gull – Vagrant. Few records, most from late spring.
Franklin’s Gull – Small number found each year, especially in spring and fall migration.
Little Gull – Vagrant. Few records, most from winter and early spring.
Lesser Black-backed Gull – Vagrant. One record.
Swallow-tailed Gull – Vagrant. One record.