Bird of the Month: Glaucous-winged Gull, Western Gull, Herring Gull
By Andy McCormick
Scientific Name: Larus glaucescens/ Larus occidentalis/ Larus argentatus
Length 26 in 25 in 25 in
Wingspan 58 in 58 in 58 in
Weight 2.2 lb 12.2 lb 2.5 lb
AOU Band code GWGU WEGU HEGU
In this article we will focus on the adult forms of the three most common pink-legged gulls seen in Western Washington in winter, plus the hybrid of the Glaucous-winged and Western Gulls. Many observers now say that this hybrid gull is the most commonly seen gull of them all. The presence of this hybrid gull in Western Washington makes gull identification very confusing for many birders.
In the Northwest the Glaucous-winged Gull is the largest pink-legged gull and it is helpful to learn it well. It is abundant in Western Washington and all other pink-legged gulls can be compared with it. The Glaucous-winged is the only large gull in which the wing tips are the same gray color as the mantle, the back and wings taken together when the wings are spread (Alderfer). In breeding plumage it has a white head and yellow bill with a red spot at the gonys, the sharp angle where the tip of the lower mandible begins to curve upward. The eyes are dark with a pinkish orbital ring. In winter, the head becomes marked with dark gray streaks.
The Western Gull is of similar size and weight as the Glaucous-winged, but can be separated from it by its dark gray mantle and even darker wing tips. The bill is bulkier than the Glaucous-winged and colored a brighter banana yellow. It also has a red spot at the much heavier and thicker gonys angle. The eyes can vary from yellow to yellow with dark marks and the orbital ring is yellow. The head is white and stays white all year long. The color of the bill and orbital ring can be duller in winter, but the mantle will stay dark. The Western is the darkest large gull along the West Coast of North America.
The hybrid of the Glaucous-winged and Western Gulls is very common. So much so, that it has been given the informal name of the “Olympic” Gull. Westport, WA is considered by many to be the center of the hybrid zone of the northern Glaucous-winged Gull and the southern Western Gull. The appearance of hybrids will vary considerably. Glaucous-winged looking gulls with light mantle, dark wing tips and dark eyes are likely to be hybrids. This is the type of GWGU x WEGU hybrid we see most often. However, Western looking gulls with lighter mantle and dark streaking on the head are also likely to be hybrids. Any gull that looks like a Glaucous-winged, has a dark eye, but has dark wingtips is most certainly a hybrid.
In winter several other pink-legged gulls migrate south to Western Washington. Thayer’s Gull (L. thayeri), Glaucous Gull (L. hyperboreus), and Herring Gull join the resident gulls. The Herring is the most widespread pink-legged gull in North American but visits Washington only in winter. It is the most common of these three winter visitors and can look much like a GWGU x WEGU hybrid. However, the mantle of the Herring Gull is a lighter gray than that of the Glaucous-winged and the wing has black wing tips. The eyes are a pale yellow and the orbital ring is yellow when breeding and it can become duskier in winter. The bill is large but does not have the bulk of either the Glaucous-winged or the Western. It has a red spot at the gonys, but the angle is not as pronounced. The head becomes gray-streaked in winter when the gulls are in the Northwest.
For a refresher on the three yellow-legged gulls, Ring-billed, Mew and California, please refer to the Bird of the Month column in the March 2010 edition of The Corvid Crier.