Gulls are considered by some as the most challenging group of birds in the ABA area to identify. As challenging as it is, why not try to learn today how to differentiate these marvelous creatures!
This time, we will go deep into the identification of six gull species (Herring, Ring-billed, Iceland, Glaucous, Lesser Black-backed, and Great Black-backed) plus two Iceland Gull subspecies, covering and explaining everything from greater primaries to the orbital ring.
Lets first start off with the Iceland Gull, a complex of subspecies that is still debated today over the species status! THIS ARTICLE IS ABOUT WINTER GULLS ONLY, SOME OF THESE TIPS MAY NOT HELP YOU IN THE IDENTIFICATION OF SUMMER BIRDS!
Kumlien’s Gull – Larus glaucoides kumlieni
The kumlieni subspecies of Iceland Gull has always been a challenging identification-even for the experts. They are variable in the color of their outer primaries (P6 – P10), and look very similar to many other gull species. So how can you ID it? In-flight: Let’s first look at the outer primaries on the underwing. Are they grey, white, or black? If they are a light grey, then that will help differentiate it from other species and subspecies of Iceland Gull. Another field mark to look at is its size. They are generally in between the size of a Herring and a Ring-billed. The next step is to snap a photo of the gull and try to ID it for yourself. Standing: Okay, I have to admit that this is quite hard, but you can still ID it! First look at the greater primaries. They should be light grey. Next, check the leg color. It should be a dark pink. Lastly, check out how much streaking is on the head. If it is sparsely streaked, then you have yourself a good candidate for a kumlieni Iceland. 1st year: Look for a light-colored mottled bird with no black at all in the wings. Now you have eliminated many possible species. But to be sure it is, in fact, a kumlieni Iceland, we should look at the size compared to nearby gulls (in most cases Herring and Ring-billed). It should be in between the size of both of them, any bigger, and it is probably a Glaucous. Lastly, look at the bill. Is it all black? If so, combined with everything mentioned above, you should have a fairly good ID on this tricky bird! 2nd year: In this cycle of Kumlien’s Gull, the bird may appear very pale. Unlike many other 2nd-year gull species, the Kumlien’s Gull looks much more uniform. The only other 2nd-year gull that looks similar to a 2nd year Kumlien’s is Glaucous, which is usually bigger. Now we have to look at the bill proportion. If the bird in question is a Glaucous, then it would have a very large stalky bill, where as Kumlien’s, would have a smaller bill in proportion to its head. We can also look at its overall structure. If the bird is fairly slender, it is almost definitely a Kumlien’s as Glaucous Gulls tend to be more stalky. 3rd year: Very similar to an adult, but may have a more pale bill and usually shows some brown on the wings and tail.
Thayer’s Gull – Larus glaucoides thayeri
This bird has a long history of being lumped with species and then split again- just last year the American Ornithological Society (AOS) lumped it with Iceland Gull. Overall, for most people, this is the hardest gull to identify. They vary greatly in the color of their outer primaries (sometimes almost reaching the darkness of a Herring and other times almost reaching the greyness of a kumlieni subspecies Iceland), and they are roughly the same size as a kumlieni subspecies. Now, we will move onto how to identify this bird. In-flight: Look at the underwing. Is the black limited to the tips and the inner webs? If so, it is time to look at the upperwing. It should look similar to a Herring or Ring-billed. Again though, I would get a picture and look in a guide to make sure that you have a correct ID (at least when you start out with learning gulls). Standing: This can be very tricky. Take a look at the greater primaries. Unlike a Herring Gull, with white spots on the greater primaries, the Thayer’s has white bands when sitting (especially on P6 and P7). When starting out with gulls, I would highly suggest either 1- waiting for the bird to fly or 2- getting a good picture of it and posting it somewhere experts can ID it for you. 1st year: These birds are very similar to a 1st year Herring, however, it is possible to identify it in flight! Let’s first take a look at the greater primaries. A typical 1st-year Thayer’s will have dark outer webs on the greater primaries and light colored inner webs on the greater primaries too. 1st year Thayer’s Gulls also generally have dark secondaries and unlike a Herring Gull, the Thayer’s has a pale underwing. After you have gathered all of those field marks, you can fairly conclusively ID it as a Thayer’s! 2nd year: This cycle of Thayer’s Gulls have a grey mantle, mottled wings, and black wing tips just like most other 2nd year gulls. So how do we differentiate them? If you can you can see the eye color, the Thayer’s is dark, whereas Herring’s is pale. Most of the time you cannot see the eye color so what do you do? The best idea is look at the primaries and secondaries. Is there a huge contrast between the primaries and secondaries and the rest of the wing? If so, you are most likely looking at a Herring. 3rd year: Similar to adult, but may have some brown on the tail and wing.
Glaucous Gull – Larus hyperboreus
In my opinion, this is one of the most beautiful birds found in the ABA area. A huge pure white bird, the Glaucous Gull, is one of the most sought-after birds in the country. I remember the first time I saw one. I just stood still in awe over this magnificent bird! Enough babbling about how pretty this bird is, let’s get onto identifying it! In-flight: First off, is the bird large and pure white except for the bill? If so, you may have just had a Glaucous Gull! But wait, some Kumlien’s Gulls can reach near pure white greater primaries and the vagrant nominate Iceland (ssp. glaucoides) has pure white greater primaries. Now we have to look at the size and structure of the bird. As I mentioned earlier, if the bird in question is a Glaucous, then it would have a very large stalky bill, whereas Kumlien’s or a nominate Iceland would have a smaller bill in proportion to its head. For the overall structure, if the bird is fairly slender, it is almost definitely a Kumlien’s as Glaucous Gulls tend to be more stalky. Standing: If you see a Glaucous gull standing, your first reaction might be “Woah look at that huge white bird out there”. After you have concluded that your bird is all white, the question remains- how to tell it apart from an Iceland? Well, it is the same rule as above, with that, you should be able to get a fairly confident ID on the bird. 1st year: first-year birds are usually off-white overall. Really, the only bird you could confuse them with again is an Iceland Gull. Here is a nifty trick for separating 1st-year Glaucous Gulls from Iceland Gulls (all ssp), the bill! The bill of a first year Glaucous Gull is bi-colored, whereas all Iceland Gull first-year birds are all black. 2nd year: Like all stages of Glaucous Gulls, the only bird you could really confuse this with are all of the Iceland Gull subspecies, which can be separated by using the rule up above in the in-flight section. For porpuses of identifying what year the bird is, 2nd-year birds are usually more white than 1st-year birds but retain the some of the very light brown mottling on 1st-year birds. 3rd year: very similar to adult, but the bill more resembles a 2nd-year bird and may have a brownish wash on the tail and wings.
Lesser Black-backed Gull – Larus fuscus
The Lesser Black-backed Gull is a wintering visitor from Europe that just recently began booming in numbers across the ABA area. In fact, up until a few years ago they were listed on the ABA checklist as a code 3! In-flight: There is only one other common gull here that you could confuse this with, the Great Black-backed Gull, and separating them is fairly straight-forward! First off, is the bird in between the size of a Ring-billed and a Herring or is it a true monster in terms of size? If it is in between the size of a Ring-billed and a Herring then it is almost certainly a Lesser Black-backed. Want to be unquestionably, 100% positive though? Then we need to look at the color of the wings and mantle. They should be very dark grey but not black. Also, look at the head. On a typical Lesser Black-backed, there will be some streaking, whereas, a Great Black-backed Gull would have an almost jet black wings & mantle. Additionally, there would be no streaking at all on the head. Standing: Again, this bird could only be confused with a Great Black-backed. Unlike when it is in flight, you can see the leg color. Is it pink or yellow? Yellow means Lesser Black-backed and pink (if it is the right size) may be a very rare Slaty-backed Gull or just a Great Black-backed. 1st year: This bird can be confused with multiple species. Its size can differentiate it from Great Black-backed but not much else. First, we need to look at the wings. If it is a Lesser Black-backed, it would be very dark, eliminating all the Iceland Gull subspecies and Glaucous Gull. In a first-year Lesser Black-backed, the head will also be much lighter than the wings which is not found in a normal Herring or Ring-billed. From these characteristics, we can almost positively ID the bird. However, for beginners, I would highly suggest getting a picture and sending it to experts. 2nd year: Similar to 1st-year but it shows some dark grey on the mantle and the bill is bi-colored vs. solid black. You can use the same rule for 1st-year birds here. 3rd year: Very similar to adult but some birds may show black on the tail.
Great Black-backed Gull – Larus marinus
This bird is the largest gull in the world. It is an expert predator and robber- able to snatch adult puffins in mid-flight while ruling all the other gulls by stealing their food! In-flight: Not much can be confused with this bird. Its monstrous size along with its jet-black wings and mantle make this bird almost un-mistakable! We need to look at the color of the wings and mantle. They should be jet-black, not dark grey. Also, look at the head. On a typical Great Black-backed, there will be absolutely no streaking, whereas, a Lesser Black-backed Gull would have dark grey wings & mantle as well as some streaking on the head. Standing: Again, this bird can be conclusively identified by its size alone. You might say “then why are you telling me how to separate it from a Lesser Black-backed?”. Well, what if you can’t find anything to compare it to? First, we should look at the color of the legs. If the bird is a Great Black-backed then it will have bright pink legs, whereas, a Lesser Black-backed would have bright yellow legs. 1st-year: As I have mentioned many times, this bird can be identified just by size alone, but if no comparison is available then you will have to use other field marks. First look at the head. A Great Black-backed would have limited streaking, whereas, a Lesser Black-backed would have much streaking. When sitting, a first-year Great Black-backed looks surprisingly light-colored (like a Herring). Now, let’s take a look at the head and underside. A normal 1st winter Great Black-backed will have a very light colored head and underside -unlike a Herring which has a darker head and underside. 2nd year: Fairly similar to a 1st-year bird but it has a bi-colored bill, all white underside & head, and it starts to get black on the mantle. This bird is pretty much unmistakable. To be certain, you can use the rule for first-year birds here. 3rd year: Similar to adult but shows some brown on the wings. It may show some black on its tail and has a dark ring around the bill.
Herring Gull – Larus argentatus vs. Ring-billed Gull Larus delawarensis
Perhaps the most common gull in the US, the Herring Gull is a familiar sight. In Illinois, you commonly see flocks of 200 or more Herring Gulls in the winter and within those flocks, there can be some treasures like a Lesser Black-backed, Glaucous, etc. In-flight: Your typical gull- grey mantle & wings with black greater primaries, a yellow bill with a red gonydeal spot, and in winter, a streaked head. Here is a quick ID tip I learned from another birder about a year ago- when you’re trying to quickly ID gulls in-flight (you’re probably dealing with Ring-billed and Herring if you are in Illinois) just look at the angle of the elbow. If it has a sharper angle it is a Ring-billed, if it is a smaller angle then it is Herring. Standing: If you are trying to tell the Ring-billed Gulls from Herring Gulls then look at the size. Herring Gulls are bigger and Ring-billed are smaller. A quicker way to ID them though is to look at the leg color. Herring Gulls have pink legs and Ring-billed Gulls have yellow. 1st year: These birds can vary greatly in terms of plumage coloration- some are a lighter brown and others are a dark brown. Plumage coloration is a good way to separate these birds from Ring-billed Gulls which tend to be much lighter in coloration. 2nd year: In this stage, the Herring Gulls are fairly easy to separate from Ring-billed as 2nd-year Ring-billed Gulls are usually much more similar to the adult stage. 3rd year: Can be tricky to ID as these birds have much variation, some looking like a 2nd-year bird while others can look similar to an adult bird.
Although many view gulls one of the hardest group of birds to identify, distinguishing them can be very exciting and rewarding. I hope that the article above has inspired you to learn more about these marvelous birds. I want to give a special thanks to Amar Ayyash, whose wisdom and guidance over the last few years has given me a greater appreciation of the complexity of gulls.