Winter Gulls: The Great I.D. Challenge
Gulls are a fun challenge for birders, from beginners to experts. A few things make gulls an interesting study: they are large and conspicuous in their open habitats, so they are easy to see, easy to put a scope on, and easy to watch and study for long periods of time. Furthermore, gulls are almost always identifiable as gulls; none of this confusing warbler/vireo/kinglet nonsense!
And yet, gulls are almost impossibly difficult! (Though perhaps not nearly as difficult as Empidonax flycatchers!)
One of the reasons they are so complicated is most gull species take two or three years to achieve adult plumage, and go through multiple molts in a year. So, you may be looking at three or four gulls together that look like four completely different species, when they are actually just different ages (individuals in their first, second, third, even fourth winter of life). While North America is home to around two dozen species of gull (really only about nine are very common in California), there are around 200 unique plumages! Throw individual variation and worn vs. fresh plumage into the mix, and it's enough to make just about any birder give up!
But there is hope. There is always hope.
First, we must understand the basic plumage sequence all gulls go through. It looks basically like this:
Juvenile plumage: typically July-September. Often much darker than any other plumage; this is how young birds look after fledging, or leaving the nest.
1st winter plumage: typically October - April. This is the "first winter" of these birds lives.
1st summer plumage: the following April - August
2nd winter plumage: August - April
2nd summer plumage: April - August
3rd winter plumage: August - April. Some species only. Other species will go into adult nonbreeding plumage at this point. Gulls are often called "three-year gulls" or "four-year gulls" based on how long it takes them to achieve adult plumage.
Adult nonbreeding: August or September - April. This is usually the easiest plumage to identify. Most gulls are more numerous in California during the winter, and during the nonbreeding season, the number of gull species found along the coast increases. (Mew Gulls, Herring Gulls, and Iceland Gulls, for example, are here only from fall through spring.)
Some of these terms aren't widely accepted anymore, as new research has been done on molting. Instead of "first winter" or "first summer," you might hear "first prebasic molt" or "first prealternate molt" instead. This is due to greater understanding of molt as a cycle, where lines between seasons are blurred. Some birds may already be molting into their winter plumage as early as June, complicating our nice straightforward terminology.
In the Humphrey-Parkes system of describing molt, the terms "basic" and "alternate" plumage correlate roughly to winter (nonbreeding) and summer (breeding) plumage. For example, "first basic plumage" in the chart below is about the equivalent of "1st winter" in Sibley's illustration above.
I still think the "first winter, second winter" etc. way of describing molt is simple enough to make sense to a beginner, and it's what I learned first so I still use it. But you might hear differently from someone else. Just a warning!
Nearly universal advice for anyone setting out to learn their gulls is this: focus on learning to identify adult nonbreeding winter gulls first, before attempting to sort out 1st and 2nd winter birds. Because gulls seem like they are constantly changing or molting from one plumage to the next, winter presents the freshest plumage and the gulls that will look most like the illustrations in your field guide. (Fall and spring molts complicate things further.)
Furthermore, there will always be a greater proportion of gulls in adult nonbreeding plumage than any other plumages. There should be a fair number of first winter birds, but fewer second and third winter birds, since life in the wild is tough and many of those first winter birds won't live to become second winter birds and so on. The proportion of adult gulls in their fourth or subsequent winter is fairly high, since a gull can live up to 20 years.
It also helps to understand which gulls you are most likely to encounter. Don't try looking for rarities or even less common species right away; first, become thoroughly acquainted with the most common and abundant gulls in all their intricate variety.
In central California, where I do the majority of my birding, the most common and abundant winter gulls are Western Gulls and California Gulls, followed by Ring-billed Gulls and Herring Gulls. If you're birding anywhere else, take the time to get acquainted with the names and pictures of your most common local gulls before heading into the field. There's no sense in Atlantic Coast birders poring over the differences between Western and California Gulls when they are unlikely to encounter either one.
Now, let's tackle a few of the gulls I encountered in the last few days in Santa Cruz and Monterey counties.
Pictured above are two very common gulls, and one that is less so. Compare the dark backs and black wingtips (which are commonly mistaken for the bird's "tail") of the Western Gulls on the right with the light gray back and light gray wingtips of the Glaucous-winged Gull on the left.
And yet, gulls are almost impossibly difficult! (Though perhaps not nearly as difficult as Empidonax flycatchers!)
 |
| An intimidating scene to many a birder: a mixed flock of gulls. I see five different species of gull here. Oh, and one American Coot in the background. |
One of the reasons they are so complicated is most gull species take two or three years to achieve adult plumage, and go through multiple molts in a year. So, you may be looking at three or four gulls together that look like four completely different species, when they are actually just different ages (individuals in their first, second, third, even fourth winter of life). While North America is home to around two dozen species of gull (really only about nine are very common in California), there are around 200 unique plumages! Throw individual variation and worn vs. fresh plumage into the mix, and it's enough to make just about any birder give up!
But there is hope. There is always hope.
First, we must understand the basic plumage sequence all gulls go through. It looks basically like this:
Juvenile plumage: typically July-September. Often much darker than any other plumage; this is how young birds look after fledging, or leaving the nest.
1st winter plumage: typically October - April. This is the "first winter" of these birds lives.
1st summer plumage: the following April - August
2nd winter plumage: August - April
2nd summer plumage: April - August
3rd winter plumage: August - April. Some species only. Other species will go into adult nonbreeding plumage at this point. Gulls are often called "three-year gulls" or "four-year gulls" based on how long it takes them to achieve adult plumage.
Adult nonbreeding: August or September - April. This is usually the easiest plumage to identify. Most gulls are more numerous in California during the winter, and during the nonbreeding season, the number of gull species found along the coast increases. (Mew Gulls, Herring Gulls, and Iceland Gulls, for example, are here only from fall through spring.)
 |
| A snapshot of the page in The Sibley Guide to Birds of North America that illustrates the varying plumages of the Herring Gull. |
Some of these terms aren't widely accepted anymore, as new research has been done on molting. Instead of "first winter" or "first summer," you might hear "first prebasic molt" or "first prealternate molt" instead. This is due to greater understanding of molt as a cycle, where lines between seasons are blurred. Some birds may already be molting into their winter plumage as early as June, complicating our nice straightforward terminology.
In the Humphrey-Parkes system of describing molt, the terms "basic" and "alternate" plumage correlate roughly to winter (nonbreeding) and summer (breeding) plumage. For example, "first basic plumage" in the chart below is about the equivalent of "1st winter" in Sibley's illustration above.
 |
| This example show the Humphrey-Parkes system as it pertains to the Herring Gull. Source: https://www.allaboutbirds.org/the-basics-feather-molt/ |
I still think the "first winter, second winter" etc. way of describing molt is simple enough to make sense to a beginner, and it's what I learned first so I still use it. But you might hear differently from someone else. Just a warning!
Nearly universal advice for anyone setting out to learn their gulls is this: focus on learning to identify adult nonbreeding winter gulls first, before attempting to sort out 1st and 2nd winter birds. Because gulls seem like they are constantly changing or molting from one plumage to the next, winter presents the freshest plumage and the gulls that will look most like the illustrations in your field guide. (Fall and spring molts complicate things further.)
Furthermore, there will always be a greater proportion of gulls in adult nonbreeding plumage than any other plumages. There should be a fair number of first winter birds, but fewer second and third winter birds, since life in the wild is tough and many of those first winter birds won't live to become second winter birds and so on. The proportion of adult gulls in their fourth or subsequent winter is fairly high, since a gull can live up to 20 years.
It also helps to understand which gulls you are most likely to encounter. Don't try looking for rarities or even less common species right away; first, become thoroughly acquainted with the most common and abundant gulls in all their intricate variety.
In central California, where I do the majority of my birding, the most common and abundant winter gulls are Western Gulls and California Gulls, followed by Ring-billed Gulls and Herring Gulls. If you're birding anywhere else, take the time to get acquainted with the names and pictures of your most common local gulls before heading into the field. There's no sense in Atlantic Coast birders poring over the differences between Western and California Gulls when they are unlikely to encounter either one.
Now, let's tackle a few of the gulls I encountered in the last few days in Santa Cruz and Monterey counties.
 |
| Compare the dark backs and black wingtips of the Western Gulls on the right with the light gray back and light gray wingtips of the Glaucous-winged Gull on the left. |
Pictured above are two very common gulls, and one that is less so. Compare the dark backs and black wingtips (which are commonly mistaken for the bird's "tail") of the Western Gulls on the right with the light gray back and light gray wingtips of the Glaucous-winged Gull on the left.
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| There are three species pictured here. What are they, and which birds belongs to which species? |
In the photo above, my advice is this: pick out the adult birds first. In this case, the two large white-headed gulls are adult, nonbreeding Western Gulls. Notice their virtually unstreaked heads, pale eyes, thick bill with a red spot, and their comparatively dark mantles (backs). Ignore the brownish younger birds to start with.
Next, pay attention to the obviously different small bird in the foreground. This gull has a small, delicate bill with a faint dark ring, brown smudging on its head and neck, a dark eye, yellow legs, and a wide crescent of white at the tertials (the wing parts we can see here just above the black primaries or wingtips). This is an adult, nonbreeding Mew Gull. (The bird in the background of the photo is also a Mew Gull, but I would say it is in second winter plumage, based on the darker ring on its bill.)
Now we have two confusing birds left to deal with (or to ignore - that's perfectly fine for now also!) The first two clues I would consider are the species they are associating with (in this case, Western Gulls). There is a pretty good chance that they are younger examples of a familiar adult gull you've already identified in the area. But consider their proportions. While similar, the bird on the right has a smaller bill than the bird on the left. I would say that the brown gull on the left is a Western Gull in its first winter, and the bird on the right is a first winter California Gull (notice its lighter overall coloration and pale face, another field mark of immature California Gulls). But I am open to correction. (Thanks to an astute reader for correcting me once already!)
The photo above is backlit, so the quality of the colors is not very great. But such is the case when birding in the field. The birds in front of you and in your photos won't always look like the pictures in the field guides. Even so, we can tell that one of these birds is not like the others. In this case, we are looking at a flock of small, delicate-billed Mew Gulls, with one California Gull. The larger California Gull can be identified by its yellow legs, dark eye, streaked neck, and the presence of both red and black markings on its bill. As a rule for comparison, California Gulls are darker gray than Herring Gulls, but lighter gray than Western Gulls.
The photo above gives us a pretty good look at two Mew Gulls. Along with yellow legs, they have dark eyes and small bills that show varying degrees of a black ring. Compare the wide white "tertial crescents" on their wings to the smaller white crescents on the Ring-billed Gull below. Mew Gulls also show more extensive brown smudging on the head and neck, often forming the shape of a "shawl" while Ring-billed Gulls have finer streaks more restricted in area.
Ring-billed Gulls, pictured both above and below in text-book perfect adult winter plumage, are identified by their pale irises, yellow legs, broad black ring on the bill, and small, faint white tertial crescents.
Pictured below are several California Gulls. Look for their dark irises, medium-gray mantles, yellow legs, and the presence of both red and black marks on their bill.
Now for a few more challenges. At first glance, the gulls in the photo below look basically the same: gray and white, and all about the same size. But I see three species here. What do you think?
In the photo above, the gulls with dark gray backs and nearly pure white heads are Western Gulls. Those with pale gray backs and heavily streaked heads and necks are Herring Gulls. And do you see the third species? The gull in the center of the photo with light gray primaries (wingtips) rather than black is a Glaucous-winged Gull.
Try this one:
The lighting is poor, but what do you see? Can you count all four species pictured above?
I think I got them all. But notice I left a few out. That's okay. There will always be plenty of gulls you're just not sure about. Sometimes the lighting is weird, sometimes the bird is at a bad angle, blocked by another bird or simply too far away to make the call. Just focus on the birds you can identify, to start with.
In the photo below, it looks like another case of all the same. But again, there are four species here!
Can you pick out all four species pictured above?
The last one is much easier: The Heermann's Gull is one of our most distinct gulls, with a red bill, black legs, gray body and white head. This species is a little different in that it may be sporting breeding plumage (this striking white head) as early as December. But after muddling through all the others, it's a joy and relief to find an unmistakable and unique gull like this that really sticks out!
The last time I wrote about gull identification, I included a handy chart for comparing nine common species in California. I've updated the chart to include a little more helpful information, and included it again. Don't be afraid of the gulls. Start slowly, one bird at a time, and you will learn! And take heart - the learning process is on-going.
For further reading (and more help puzzling out those tricky gulls), I recommend the Kaufman Field Guide to Advanced Birding, which has a helpful chapter on gulls (the first edition is quite different from the second edition in light of the new terminology for molt cycles, but I think they are both helpful). Also invaluable is Gulls Simplified, which focuses more on differences in form rather than plumage variation.
And how about the five species pictured in the first photo at the beginning of this post? I see Western, Herring, California, Glaucous-winged and Mew Gulls. But I'll let you pick them out for yourself!
Next, pay attention to the obviously different small bird in the foreground. This gull has a small, delicate bill with a faint dark ring, brown smudging on its head and neck, a dark eye, yellow legs, and a wide crescent of white at the tertials (the wing parts we can see here just above the black primaries or wingtips). This is an adult, nonbreeding Mew Gull. (The bird in the background of the photo is also a Mew Gull, but I would say it is in second winter plumage, based on the darker ring on its bill.)
Now we have two confusing birds left to deal with (or to ignore - that's perfectly fine for now also!) The first two clues I would consider are the species they are associating with (in this case, Western Gulls). There is a pretty good chance that they are younger examples of a familiar adult gull you've already identified in the area. But consider their proportions. While similar, the bird on the right has a smaller bill than the bird on the left. I would say that the brown gull on the left is a Western Gull in its first winter, and the bird on the right is a first winter California Gull (notice its lighter overall coloration and pale face, another field mark of immature California Gulls). But I am open to correction. (Thanks to an astute reader for correcting me once already!)
 |
| Several Mew Gulls with one California Gull |
The photo above is backlit, so the quality of the colors is not very great. But such is the case when birding in the field. The birds in front of you and in your photos won't always look like the pictures in the field guides. Even so, we can tell that one of these birds is not like the others. In this case, we are looking at a flock of small, delicate-billed Mew Gulls, with one California Gull. The larger California Gull can be identified by its yellow legs, dark eye, streaked neck, and the presence of both red and black markings on its bill. As a rule for comparison, California Gulls are darker gray than Herring Gulls, but lighter gray than Western Gulls.
 |
| Mew Gulls and one young Western Gull |
The photo above gives us a pretty good look at two Mew Gulls. Along with yellow legs, they have dark eyes and small bills that show varying degrees of a black ring. Compare the wide white "tertial crescents" on their wings to the smaller white crescents on the Ring-billed Gull below. Mew Gulls also show more extensive brown smudging on the head and neck, often forming the shape of a "shawl" while Ring-billed Gulls have finer streaks more restricted in area.
 |
| Ring-billed Gull in adult nonbreeding (winter) plumage |
Ring-billed Gulls, pictured both above and below in text-book perfect adult winter plumage, are identified by their pale irises, yellow legs, broad black ring on the bill, and small, faint white tertial crescents.
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| Another look at an adult nonbreeding winter gull |
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| California Gulls |
Now for a few more challenges. At first glance, the gulls in the photo below look basically the same: gray and white, and all about the same size. But I see three species here. What do you think?
 |
| Three species together |
In the photo above, the gulls with dark gray backs and nearly pure white heads are Western Gulls. Those with pale gray backs and heavily streaked heads and necks are Herring Gulls. And do you see the third species? The gull in the center of the photo with light gray primaries (wingtips) rather than black is a Glaucous-winged Gull.
Try this one:
The lighting is poor, but what do you see? Can you count all four species pictured above?
I think I got them all. But notice I left a few out. That's okay. There will always be plenty of gulls you're just not sure about. Sometimes the lighting is weird, sometimes the bird is at a bad angle, blocked by another bird or simply too far away to make the call. Just focus on the birds you can identify, to start with.
In the photo below, it looks like another case of all the same. But again, there are four species here!
Can you pick out all four species pictured above?
The last one is much easier: The Heermann's Gull is one of our most distinct gulls, with a red bill, black legs, gray body and white head. This species is a little different in that it may be sporting breeding plumage (this striking white head) as early as December. But after muddling through all the others, it's a joy and relief to find an unmistakable and unique gull like this that really sticks out!
 |
| The unique Heermann's Gull |
The last time I wrote about gull identification, I included a handy chart for comparing nine common species in California. I've updated the chart to include a little more helpful information, and included it again. Don't be afraid of the gulls. Start slowly, one bird at a time, and you will learn! And take heart - the learning process is on-going.
 |
| A handy chart for identifying nine common gulls of California. Click on the image above to make the chart larger and more clear! |
For further reading (and more help puzzling out those tricky gulls), I recommend the Kaufman Field Guide to Advanced Birding, which has a helpful chapter on gulls (the first edition is quite different from the second edition in light of the new terminology for molt cycles, but I think they are both helpful). Also invaluable is Gulls Simplified, which focuses more on differences in form rather than plumage variation.
And how about the five species pictured in the first photo at the beginning of this post? I see Western, Herring, California, Glaucous-winged and Mew Gulls. But I'll let you pick them out for yourself!
I believe the second 1st year bird in the 5th image is a California gull and not a Western gull. The overall plumage is much paler than a similarly aged Western gull, and the bill is much smaller with a weak gonys and also sharply bicolored.
ReplyDeleteLooking at it again, I totally agree with you! Thanks so much for the correction! I'll fix my goof right away! :)
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