I love all the gulls. They are graceful, powerful, versatile, beautiful and intelligent. Gulls have a complex language and interact with other creatures extensively. Among the most adaptable birds out there, they have figured us out and made use of opportunities we humans didn’t intend to provide for them (think landfills, parks, fast food dumpsters, fishing boats, etc). That brings us into contact with them more than most birds, who prefer seeing us in their rear view mirror like most wildlife. A lot of people consider birds who one-up us as “pests” or “sky rats” although there are some of us who admire their clever behavior — it being an iota toward fairness considering the many things humans do to make life more difficult for them. Gulls’ versatility means they can soar smoothly but also turn on a dime, paddle efficiently but also walk. At home at sea but on land to some extent too, which is why it’s a misnomer to call them seagulls. Johnathan Livingston notwithstanding.
But that’s not what this diary is about. Inspired by an encounter with some gulls I didn’t expect a couple of weeks ago, I want to share a brief primer on how to identify gulls. I mistook those gulls for another at first, and almost missed spending lots of time for the next few days enjoying their rare visit to the beach.
How can we tell one kind of gull from another? I’ll be using as examples the gulls I see in my area, the Pacific Northwest, but the basic principles can be applied to whatever set of gulls you share your birding world with. I’ll present a “flow chart” of choices to make about an individual which should narrow down the possibilities among your set of gulls too. It’s a given, of course, that definitive ID of any possible gull you might see out there is beyond the scope of us amateur birders.
Demographics:
First, you can shamelessly use your geographic location and time of year (field guides or online sources). Migratory gulls will not be around during some months, so you can eliminate them as possibilities — USUALLY. There are often cases of a bird getting left behind or wandering outside its normal range, but IDing those birds boosts us into expert status (which ain’t me). You can also use typical habitat behavior, eg. landfill visitor or not, offshore or beach. Social behavior can be a good clue too, since some species are especially gregarious.
In my area, only one species is year-round (Glaucous-winged, hereafter GWGU) (and its hybrid x Western), with four others common here in various months of the nonbreeding season (Mew gull aka MEGU July-May, California gull aka CAGU July-October, Heermann’s gull aka HEGU July-October, Bonaparte’s gull aka BOGU Feb-May and Aug-Sept). So if I see a gull in January, it’s almost certain to be a GWGU or a MEGU.
Most gulls look somewhat different between breeding and non breeding seasons, so time of year helps cue you to visual differences. A few gulls like Bonapartes change radically (black head, breeding, to white head with black cheek spot, nonbreeding) but most gulls shift from pure white head, breeding, to streaked/smudged, nonbreeding). Around here Western gulls do not darken in winter so if you see a white-headed gull in the off season that’s an easy way to pick a Western out of a crowd.
The dates in the photos are to show what season it is. They come from different years.
Size:
Turning to the appearance of a gull, the first thing I’d look at is whether the gull is large, medium and small. The difference can be considerable! Size is difficult to ascertain when they’re overhead, with no context. However even there you can get a sense by how fast they move: the smaller the gull the more quickly maneuverable. On the ground or compared to other birds it’s easier to judge a gull’s size.
In my area, the large gulls are GWGUs and Olympic gulls (hybrid of GWGU x Western) plus a couple rarely found here, Herring and Western gulls. Medium-size gulls are Californias, Heermann’s and the rarely seen Ring Bill and Iceland gulls (previously Thayers). Small gulls are Mews and Bonaparte’s. Roughly 95% of the gulls seen in my county are the six common ones named. It’s possible I might come across one of the other four, but I’d have to have a good photo of it to tell, using visual clues.
Here are some size comparisons:
Color:
Almost all gulls are largely white, with shades of grey and black or brown on their mantle and wings. It’s a coloration pattern that suits their primary home at sea, camouflaged against the sky invisible to fish, and seen from above blending in with a choppy sea surface. Heermann’s gulls are an exception: grey all over except in breeding season when their heads are white. These are the easiest gulls to ID around here.
All our other gulls are white below with grey wings and black wingtips (including the rare gulls) except the GWGUs, whose wings are, well, all glaucous (grey). There are shades of grey, but those are hard to distinguish unless you are comparing them: Californias and Westerns are a darker shade of grey than the others.
Bill shape:
Gulls occupy somewhat different niches, so their bills are varied in shape, from big hurky crunching types to thin delicate snatching types. Generally speaking the bigger the gull the hurkier its bill relative to its body size, so if you can’t judge a gull’s size per se, the hurkiness of its bill is a pretty good way to get to that. Coloration and markings of bills can be distinguishing too, but that varies far more with a gull’s age. We’ll get to immatures later.
Leg color:
All gulls have webbed feet for swimming and walking, not so much for perching, although they manage that pretty well too. But their legs and feet come in various colors, so if they aren’t swimming, legs hidden in the water, that’s a good, and often definitive, clue. GWGUs (and Herring, Western, and Iceland) have pink legs. Californias, Mews (and Ringbills) have yellowish legs. Bonapartes have orangey legs that could be mistaken for pink, but they are the one gull, as an adult, with a black rather than yellow bill, so are distinguishable that way.
Unfortunately for ID, leg color changes radically in many gulls as they mature. Mew gull legs are yellow as adults but dull pink as immatures. California gull youngsters have blueish grey legs while adults’ are yellow. The size and shape of the gulls is the same but colors vary. This is true for bill color too.
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Identifying Immature Gulls
So we’ve seen some fairly distinctive differences between my adult gull species, which means IDing adults is at least attemptable. You can do the same for yours. Luckily most gulls are adults since they live 15-30 years, with their immature stage lasting only 2-4 years. It also helps that most of the time if a youngster is in a flock of mostly one species, the chances are good it’s one of those.
But there’s no question that IDing immature gulls can be a major challenge. Best I can do here is to present some basic principles. In general, once gulls fledge they are a streaky mottled brown no matter what the species, so you have to look at their overall size and bill shape. Use your demographics too: what gulls are likely to be around at the time in your location? What’s the habitat they’re in (offshore, beach, park, quiet or turbulent water)? Are they hanging around in a flock or just a few (keeping in mind during breeding season all gulls are gregarious)?
We can also look at how immatures interact with the adults around them. Gull species mix it up often enough when roosting or feeding, but an interaction like this is pretty unambiguous.
Toughest ones to ID are when there aren’t obvious clues or adults around. The plumage during the years between juvenile and adult stages look more and more like adults. Less brown more grey and white.
Why it’s fun to ID gulls, for me
Identifying gulls is a bigger challenge than for other birds who have more distinctive colors and patterns, as well as having a wider range of body shapes and sizes. In addition, most birds become adults within a year, so you don’t have as many immature-plumaged individuals flying around to confuse the ID challenge. So why go to the effort? They are beautiful, regardless who they are.
For me, it’s compelling to get a glimpse into the lives of these wild creatures. Why are they doing what we see them doing? How do different individuals of one kind interact with each other, in their behavior and communication? Does the age of a bird make a difference in bird society? What happens when different kinds of gulls overlap for feeding or roosting? How is the lifestyle of birds different arriving or departing on migration, in summer and winter? How do they get food? Since I can never know most of what goes on in their life, every small bit of information I can gather helps me gain insights about them.
I mentioned at the start that I mistook some birds one day. There were about 50 swooping and wheeling over the quiet bay near my house. Small birds, small bills, snapping up food near the surface, eating on the wing, lots of chasing going on. I see Mew gulls in this bay frequently, most days, and they feed like that. I was standing by the shore admiring the action, taking pictures as best I could, when something didn’t look right about the ones passing close by me. I looked at my pictures later on and discovered these were a flock of Bonaparte’s gulls! Very unusual to see them so close to shore, and over quiet water. I’ve only seen them offshore over turbulent tidal currents. Evidently they’d found a concentration of baitfish, and were enjoying a feast. I went back out to watch them there and in the neighboring bays over the next few days, mornings and afternoons. Then they were gone, continuing on their way to other fish feasts.
If I hadn’t paid attention to who they were, I’d have missed all that drama. I’ve been thinking about them and watching for Bonaparte’s ever since.
Helpful resources:
Field guides have pictures and seasonal range maps. My favorites are Sibleys and Stokes.
Birdweb is a Washington state site that has info about when birds are present in different parts of the state. Also some natural history. becomewww.birdweb.org/...
eBird is a good source for local sightings. You can pull up a bar chart for your county showing how abundant bird species are at different seasons. ebird.org/...
Cornell Ornithology has lots of natural history info and is pretty good for ID, showing similar species. www.allaboutbirds.org/...
Any interesting gull encounters you’ve had with gulls in the natural world? Any tips or challenges about gull ID you can share?
And of course the Dawn Chorus is open now for your birdy experiences from the past week.