Birder’s Notebook: Glaucous-winged Gull –– Taking notice of one of the region’s less common gulls

In recent weeks, large flocks of gulls lingered along then-open coastal waters of Norton Sound, poised to dive in mass to feast on schools of saffron cod (tom cod) and rainbow smelt that move into the shallows to spawn at this time of year.

It is an amazing spectacle to witness the convergence of gulls, seals and belugas as these feeding frenzies suddenly unfold, and an exciting demonstration of the richness and energy of the marine ecosystem at our doorstep.

At times hundreds of gulls plunge simultaneously into the frigid water in a noisy, tightly packed tangle of wings and squabbles. Thievery is rampant in the chaos. Lucky gulls quickly slurp smelt and hasten to reposition the larger cod to swallow them headfirst, or to fly away with their prize before losing it to a competitor.

The vast majority of the gulls in these feeding frenzies are glaucous gulls, the region’s most common and abundant gull. They breed here and throughout the circumpolar north, and were the focus of a previous article.

But if you look closely, amidst the glaucous gulls you may often see two other very similar, large gull species in the mix––the herring gull and the glaucous-winged gull. These gulls are far less common here, but their numbers increase in the fall when juveniles and adults come to scavenge and fish along the shores of Norton Sound.

Mature glaucous, glaucouswinged and herring gulls can be distinguished by noting the color of their wingtips. Binoculars help a lot! Glaucous gulls have entirely white wingtips. The herring gull has prominent black markings on its wingtips. The glaucous-winged gull, the subject of this article, can be picked out of the crowd by gray markings on its wingtips that are the color of the bird’s gray back.

The glaucous-winged gull is the most common gull in the southern Bering Sea and along Alaska’s southern coast, breeding from British Columbia to the end of the Aleutian chain and northward through the Bering Sea to at least St. Matthew Island. But in this region and throughout the northern Bering Sea, their niche is filled by the arcticbreeding glaucous gull.

On the Seward Peninsula and at St. Lawrence Island, small numbers of glaucous-winged gulls show up during spring migration and can be spotted along the coast and at landfills amidst newly arriving glaucous gulls. Fewer are seen during the breeding season, but their numbers increase in August and September when immature birds and adults arrive to feed along the shores of both Norton Sound and St. Lawrence Island.

Glaucous-winged gulls are almost entirely a coastal species, generally found in intertidal habitats and seldom venture far inland except to visit landfills or to follow salmon streams to scavenge on carcasses. In more southerly brown bear habitat, they boldly mingle with fishing bears, grabbing whatever scraps they can get.

When the gulls fly inland to spawning areas or landfills during the day, they usually return to marine waters to bathe, forage at low tide and spend the night.

Open, grassy hillsides on scattered offshore islands along the Pacific coast and southern Bering Sea are preferred nesting sites. Glaucouswinged gulls usually nest on the ground near the coast, often in large colonies.

Like most gulls, glaucous-winged gulls are omnivorous, eating a diverse diet of animal and plant materials. They walk, swim and fly along the coastline searching the mud, sand, rocks and waters for prey including invertebrates, fish and their eggs, chicks and eggs of other birds (including of their own species), small birds and mammals.

They may plunge into the water from flight to catch or steal prey from other gulls or from diving seabirds that bring food up from depths the gulls cannot reach themselves. They drop shellfish and crabs on rocks to break them open. Besides taking live prey, they perform a useful function as scavengers cleaning up carrion on land and water. Berries and other plant materials are eaten. Landfills, fish processing facilities and fishing boats all draw these opportunistic gulls.

Glaucous-winged gulls are large and aggressive with few enemies to fear. Still, ravens, jaegers and foxes sometimes take their eggs and young. Bald eagles can prey on juveniles and adults, but territorial defense by other gulls of their own kind can result in higher mortality than predation.

Glaucous-winged gulls winter as far north as the central Bering Sea, ranging at times out to sea to feed away from the coast. Though outnumbered by glaucous gulls, a few of these gulls, in their handsome winter plumage with mottled gray heads, are likely to remain in the region as long as there is open water in which to feed.

Opportunistic birds such as glaucous-winged gulls are well adapted to cope with changes in their environment and they seem to be doing well. In recent decades their population has been relatively stable and their breeding range has expanded northward. An increasing number of juveniles seen in early fall both at St. Lawrence Island and in Norton Sound suggest that some glaucouswinged gulls may now be nesting in the region.

Identifying gulls is notoriously confusing. Glaucous, glaucouswinged and herring gulls are not only similar, but until they reach maturity at age four, their appearance changes every year. Also, they are closely related and can interbreed, producing hybrids that add further confusion. But if you grab your binoculars and focus on the wingtips, you can begin to sort out who’s who.

WINGTIPS ARE KEY TO GULL ID—This photo shows the three large gull species most regularly seen in the region. In this photo the birds with white wingtips (all but three) are glaucous gulls, by far the most common gull here. Some are still in close to breeding plumage with white heads. Others are molting into nonbreeding plumage with gray-brown flecking on their heads and necks. The tan bird on the far left is a juvenile glaucous gull. The gull with black-and-white tipped wings raised is a mature herring gull in winter plumage. In the photo, below and in front of the herring gull are two glaucous-winged gulls on the water with gray-andwhite wing-tips. They are going into winter plumage with gray-brown mottling on their heads and necks. All of these species have reddish pink legs.*

FEEDING FRENZY— A chaotic flock of gulls had just descended into slushy waters on a school of saffron cod at the mouth of the Snake River in late November. By that time, the smaller gull species (black-legged kittiwakes and short-billed gulls) had left for the winter and only the three, large, similar-looking gull species remained. With binoculars, if you know what to look for, you can begin to sort out who’s who, even in a feeding frenzy. The vast majority of these gulls are glaucous gulls with all white wingtips, but you can pick out a few glaucous-winged gulls with gray-and-white wingtips (lower left on the water and upper left hovering) and a herring gull with black-and-white wingtips (upper middle, in flight.)