Editor's Note - Our main features this month are the first 2 of 3 Gull Identification articles by Steve Emmons. Those of you who saw his program earlier next year benefited from his interest in this area; we thought we'd share the fruits of his interest in this difficult area with the rest of our readership. You may want to have a field guide [or, better yet, a gull ID book] handy as you read these articles!

This is the first in a series on the identification of the various plumages of the common gulls of northern California. Part 1 defines basic terms, and describes molt sequence and the various plumages of the three most common gulls in the Sacramento Valley: ring-billed, California and herring gulls. Part 2 will cover western and glaucous-winged gulls and their hybrids, while Part 3 will summarize the plumages of the other gulls which are relatively common: Bonaparte's, mew, Heermann's and Thayer's gulls.

In addition to the standard field guides, the following references are recommended to help with identifying gulls: "Gulls: A Guide to Identification" by P. J. Grant, and "Seabirds: An Identification Guide" by Peter Harrison. The best reference I have found is "The Advanced Birding Video Series with Jon L. Dunn." Video 1 covers 13 species of large gulls and Video 2 details 14 species of smaller gulls.

A lot of beginning birders avoid studying gulls because the group is one of the more difficult to identify species. Why is this? First of all because there are quite a few species, as many as 23 species have been reported in California. In addition to going through as many as 11 identifiable plumages between juvenile and a 5th year adult, there is also a lot of variability between individuals of the same species and age. Plumage descriptions should be taken as general - almost all characteristics are variable. To make matters worse, there is frequent hybridization between species of gulls.

That's the bad news. The good news is they are relatively easy to study - I haven't seen too many gulls skulking around in thick brush or hiding in the tree tops. They are certainly bigger and easier to identify than Empidonax flycatchers and fall warblers.

The best time to study the various plumages of gulls is in the winter, especially early winter (November to December), when most of the birds possess fresh plumages and distinctions between various age groups are most distinct. During fall and spring their patterns are complicated by molt, and during summer the plumages of some, especially one year old birds, may be incredibly worn.

When watching a flock of wintering gulls, keep in mind that 1st winter and adult gulls are generally the most common, 2nd winter birds are less numerous, and 3rd winter gulls are scarce. This is because many 1st winter birds will not live to their second winter, and even fewer will survive to a third year. Somewhat fewer will make it to the fourth year, but at that point a four-year gull is in adult plumage, and the combination of the 4th winter with all subsequent winter plumages (large gulls may live up to 20 years) makes the adult plumage relatively common.

I will try to minimize the amount of special terms used to refer to parts of the body. However, there are a few terms that I will use throughout this series: (1) the gonys is the thick part of the lower bill, (2) the gonydeal angle refers to whether the gonys is large (e.g. "sharp," "pronounced," or "prominent") or not, and (3) the gape is the corner of the mouth which often becomes very colorful during the breeding season. It is important to know the following feathers of the wing: (1) the primaries are the large flight feathers on the outer part of the back edge of the wing, (2) the secondaries are the flight feathers on the back edge of the wing between the primaries and the body, (3) the tertials are the three innermost secondaries closest to the body - they cover the base of the primaries when the wing is folded on a resting bird, (4) the wing coverts are the rows of small feathers which cover the front of the wing (lesser wing coverts) extending back to the base of the primaries and secondaries (greater wing coverts), and (5) the scapulars are the feathers which cover where the wing joins the body, forming the shoulder of the folded wing. Some gulls have relatively large subterminal white spots or mirrors near the tips of the outer primaries.

Two kinds of change affect plumage: (1) the obvious abrupt change caused by molt when certain feathers are dropped and replaced with new feathers, and (2) the more gradual and constant change caused by the wear and fading of feathers.

Among gulls, molt occurs mainly during specific periods of the year. The head and body plumage is molted twice each year, once in late winter and spring (usually between February and May) and once in late summer and fall (usually starting in June or July and ending by November). Wing and tail feathers are generally replaced only once a year during the late summer-fall molt. Because these feathers are held longer, the tail and wing feathers are especially subject to the effects of wear and fading. This is particularly noticeable in one year old gulls during their 1st summer.

The timing of the molt can vary considerably among individuals of the same species. In late winter you can easily see gulls in winter and summer plumages standing next to each other. Immature gulls generally molt earlier in the season than adults, particularly during the fall molt because adults usually delay their complete molt until after they are finished breeding.

Don't forget to study gulls in flight. In general, gulls are more difficult to identify at rest than in flight. Many of the best field marks, especially for immature birds, involve details of the patterns in the wings and tails. These details are usually obscured when the birds are at rest.

Keep in mind that the larger the gull, the longer it takes to obtain an adult plumage. Small gulls like Bonaparte's obtain their adult plumage in the second year after hatching. Medium-sized gulls like ring-billed are "three-year" gulls while large species like western gulls take four or possibly even 5 years to obtain their adult plumages. The larger the species, the more immature plumages.

The following is a typical sequence of the nine plumages for a "four-year" gull: (1) juvenile is the first plumage with "normal" (not downy) feathers, (2) 1st winter is acquired by a post-juvenile molt of the head and body feathers which usually occurs between July and December, (3) 1st summer is acquired by a head and body molt between January and May, (4) 2nd winter is acquired by a complete molt occurring between May and October, (5) 2nd summer is acquired by a head and body molt from January to April, (6) 3rd winter is acquired by a complete molt between June and October, (7) 3rd summer is acquired by a head and body molt from January to April, (8) adult winter is acquired by a complete molt from June to November, and (9) adult summer is acquired by a head and body molt between January and April. This last plumage is the plumage of breeding birds. Most gull species show head and neck patterns that are different in winter than in summer, even after they obtain adult plumages. Some individuals of the largest species may require 5 years to fully obtain all of the adult features. In these cases, the bird goes through 4th winter and 4th summer plumages before molting to the adult winter plumage.

Since the ring-billed gull is one of the most common species throughout most of North America, it is an excellent species to begin with. Learning to identify the 7 plumages of this three-year gull will enable you to compare other species to it. This is probably the most common species of gull in the Sacramento Valley. The ring-billed gull is medium-sized with a round, dove-like head and thinner bill than on larger gulls. The bill lacks a pronounced gonydeal angle and generally has a long slope on the top surface of the bill towards the tip.

Ring-billed gull - juvenile. The juvenile plumage is similar to the 1st winter, except the back and scapulars are scaly brown, the spotting below is more extensive, and the bill is more black.

Ring-billed gull - 1st winter. The 1st winter plumage has a pale gray back, pale underparts, brownish wings with black outer primaries, and brown streaked head and body markings. There is a distinct brown bar on the upper surface of the forewing. Pale inner primaries contrast with dark outer primaries and secondaries. The wing linings are mostly white. The white tail has a medium-wide brown tail band and light brown spotting on the rump. The pink, dull yellow or greenish-yellow bill has a black tip. The legs are flesh-pink in color.

Ring-billed gull - 1st summer. The 1st summer plumage is similar to the 1st winter but with a whiter head and body, paler wing pattern, and usually a band on the bill. The base color of the bill and legs is yellowish.

Ring-billed gull - 2nd winter. This plumage is similar to the adult winter, except for a wider band on the bill, smaller white tips on the primaries, blackish subterminal spots on the tail forming a partial band, and sometimes dark spots on the secondaries (visible in flight). The wings are a uniform gray with black on the outer primaries and outer primary coverts. There is usually one small or no mirror, and the white primary tips are tiny or lacking. There is usually dusky streaking on the head. Some birds have spotting on the sides of the body. The color of the legs and base of the bill is usually greenish-yellow, sometimes yellowish, greenish-gray or gray. Most have pale eyes but some retain dark eyes.

Ring-billed gull - 2nd summer. The 2nd summer plumage is similar to the 2nd winter, except the head is white or lightly marked. The bill is yellow with a well developed black band. The eyes are pale in color.

Ring-billed gull - adult winter. Adults have pale gray backs and wings with black primaries. There is usually one small white mirror on each of the outer two primaries and prominent white tips to all the primaries. The white undersurface of the wings contrasts with the black in the primaries. The pale gray tertials are tipped with white but the contrast is barely evident. The yellow bill has a black subterminal band. The eyes are pale yellow and the legs are yellow or greenish-yellow. The head is streaked with brown in winter.

Ring-billed gull - adult summer. This plumage is similar to the adult winter but without brown streaks on the head, the white primary tips may be reduced or lacking, and the bill and legs are brighter yellow. In the adult summer plumage, an orange gape and vermillion-colored eye ring are evident.

Another common species in the Sacramento Valley is the California gull. This is a medium-sized gull that has a relatively thin bill with no pronounced gonydeal angle. Compared to the ring-billed gull, it is longer bodied and slimmer when perched, with proportionately shorter legs and a rounded head with sloped forehead. In flight it is longer-winged and distinctively skinny-bodied (with a flat or often slightly concave profile to the underparts behind the bulge of the breast). The bill of a California gull is longer and thicker than the ring-billed gull's with a relatively steep curve on the upper surface near the tip. The eye is dark in all ages. Unlike the ring-billed gull, the California gull takes four years to reach the adult plumage.

California gull - juvenile. Juveniles are usually very dark overall with light mottling on the underparts, and they have all dark bills.

California gull - 1st year. 1st winter birds are highly variable but generally they are mottled gray-brown above and somewhat lighter below, usually palest on the throat, breast and upper belly. The scapulars are finely checkered and often show some gray. In flight, they show dark primaries and two dark bands on the inner wing (dark secondaries and greater secondary wing coverts) that contrast with the lighter, mottled gray-brown forewing. There is only a barely evident pale window on the inner primaries which shows less contrast with the outer primaries than is seen in 1st winter ring-billed gulls. The tail is dusky-brown with no distinct band. The rump is checkered or barred brown and white, and is fairly uniform with the back coloration. The bill is two-toned with a sharply defined pale flesh base and black tip. The legs are dull flesh or pinkish.

California gull - 2nd year. This plumage is very similar to the 1st winter plumage of the ring-billed gull. The medium gray back is darker than on ring-billed gulls. The brown wings are more uniform and less barred than in 1st winter California gulls but the pale windows on the inner primaries are more prominent. The white rump contrasts with the gray back and largely black tail. A variable, but often heavy, amount of brown streaking is present on the head and neck in the winter. The bill is distinctly blue-gray or grayish-green with a dark tip. The legs are distinctly grayish-green.

California gull - 3rd year. They are similar to the adult plumage except for variable amounts of black on the tail, forming a narrow or broken tail band. The black on the wingtips is less well-defined with small or no white primary tips and a small mirror on the outer primary. The wing coverts, secondaries and tertials often have brown or black splotches. The bill base and legs are often grayish-green. The bill shows more of a blackish ring than on adults.

California gull - adult winter. The upperparts and wings are medium gray, obviously darker than in ring-billed and herring gulls. In flight, the wing-tip pattern is similar to the ring-billed gull's, but the black is slightly more extensive with larger mirrors, and the white trailing edge of the wing is more prominent. From below, the darker gray of the secondaries shows through to form a faint gray subterminal band which contrasts with the white trailing edge of the inner wing and the underwing coverts. This contrast is lacking on the undersurface of the wings of ring-billed gulls. The head and back of the neck is heavily streaked and spotted with brown in the winter. The greenish-yellow bill has a red spot on the gonys and a black subterminal mark which often forms a thin ring around the bill. The legs are often greenish or gray-green in winter.

California gull - adult summer. This plumage is similar to the adult winter plumage except for a whiter head and neck. The bill is brighter yellow with a red spot on the gonys and a black subterminal mark which is often confined to the lower bill or occasionally lacking. The gape is bright red. The dark eye is surrounded by a bright red eye ring. The legs are yellow or greenish-yellow.

The herring gull is a winter visitor to our area and can be fairly common at times. It is a large, relatively long-winged gull with a long, sloped forehead and moderately flat crown. The bill is long but not particularly thick with a moderate curve to the upper surface towards the tip and no pronounced gonydeal angle. The legs are pink in all plumages. Herring gulls take four years to mature.

Herring gull - juvenile. The whole plumage is fresh and unworn. They have a dusky head and underparts streaked with gray-brown, brown upperparts and rump, neat scaly pattern on the back and scapulars, and a dark tail with a pale tip. There is often some pale visible at the base of the tail when fully spread. The bill is almost entirely black.

Herring gull - 1st year. 1st winter birds are similar to juveniles, except the head and sometimes the underparts are whiter. They are brown overall with dark brownish-black primaries and tail. The rump is mottled brown and uniform with the remainder of the upperparts. In flight, the wings have a pale panel on the inner primaries which contrasts with darker outer primaries and secondaries. This is visible from above and below. The head can be very pale with a dark eye. The dark bill has a variable amount of pink at the base, some may have lots of pink similar to a California gull (particularly in late winter). 1st summer birds have whiter heads and underparts, paler barred upperparts, and worn and faded wings and tails.

Herring gull - 2nd year. 2nd winter birds have extensive dusky streaking on the head, pale gray on the back and scapulars, and a variable amount of gray and brown in the wings. In flight, the wings have dark outer primaries and secondaries separated by pale inner primaries. The underparts and rump are white with variable amounts of dark streaking. The black subterminal tail band is narrower than in 1st year birds and contrasts with a whitish rump. The pink or yellow bill has a dark tip. The eye is usually pale by late winter. The 2nd summer plumage is similar to 2nd winter, except for a whiter head and underparts, and uniform pale gray back which may have a few brown feathers. The wings and tail become very worn and faded.

Herring gull - 3rd year. 3rd year plumages are like the adult winter but some brown exists on the body and wing coverts, and the tail has a brown subterminal band. The wings have much black on the coverts of the outer wing, less prominent mirrors, and smaller or no white on the tips of the primaries. The bill is not as yellow as an adult's and possesses a black subterminal band or smudge mark. The eye is a pale yellow. The head has dusky streaking in the winter and is white in the summer.

Herring gull - adult. The adult has a pale gray back, scapulars, upper wing coverts and secondaries, similar in color to the adult ring-billed gull's. The black primaries are tipped with white and the two outer primaries have a white mirror. In flight, the outer wings are less extensively black with smaller mirrors than in ring-billed and California gulls. The yellow bill has an orange spot on the gonys. The eye and eye ring are yellow. In winter the head, neck and sides of the upper breast are extensively streaked with dusky coloring. The adult summer plumage has a white head, and small or no white primary tips due to feather wear.