Mind the Migration! Alert for the Month of December

This month, we are taking a look at a few gull species you can keep an eye out for in or near Nebraska. Of the many species that spend their summers in the Arctic, three will be paying this Midwest state a visit as they migrate to warmer latitudes for the winter. We’ll give you the ins and outs of how you might be able to distinguish them from your more usual, resident gull neighbors.

One skill that can often intimidate budding birders to learn is being able to identify not only the species of bird they are looking at, but also what its sex is. For some species, the differences in appearance between males and females of the same species (or sexual dimorphisms) are straightforward enough even for true novices to pick up. For example, the Northern Cardinal male is notoriously bold in a bright red allover plumage with a contrasting black mask while the female of the same species is a more subtle tan color with only streaks of that iconic red running through her crest, wings, and tail. In other cases, the differences can be more subtle. For the American Black Duck, adults have remarkably similar plumage and only differ in bill color. The male’s is yellow while the female’s is a duller, olive color.

To complicate things further, many bird species replace their feathers between breeding and wintering seasons, especially when the male is flashier than the female. One species that shows this is the American Goldfinch. In the spring and summer, the breeding plumage of the male is the familiar cheery yellow all-over with a black forehead, black wings with white striping, and peachy legs and bill. By the time they settle into their wintering grounds, they have replaced the bright yellow with a more drab, buffy plumage that looks like the female color pattern. Some dull yellow can still be seen on the head, and the black wings now feature more prominent, but less bright white wingbars.

The birds we are highlighting this month belong to the family Laridae. This family also includes terns, skimmers, and noddies, but gulls are the primary source of headache for many North American birders. Unless you’re looking at large, white-headed gulls that are standing next to each other in a mated pair, you can pretty much forget about trying to sex them by sight (“to sex” is a verb meaning “to determine the sex of!”). Sexual dimorphism in gulls is limited to differences in size, with males larger than females, and some subtle differences in head and bill shape or size. Where we run into complications in identifying gulls is in determining the age of the bird. Most gull species not only have differing wintering (or basic) and breeding (or alternate) plumages, but also can look differently in each of the first, second, and even third years of their adult lives in the same part of the year before reaching their adult plumage. To add insult to injury, most gull plumages are monochromatic overall with black, white, gray, and brown dominating the color palette of their feathers… and many gull species like to hang out in flocks of mixed species. Oof.

So how might you figure out whether the gull you’re looking at is one of these incoming species instead of your usual residents? We can rule out some factors to narrow the options. One measure to take is to consider where you are birding geographically. Using our location and time of year, we need only rule in known residents (and thus, rule out the others) as the species we need to distinguish from our visitors. If you’re reading this post with reference to Nebraska, or not too far from Nebraska, we can rule in the Bonaparte’s Gull (which doesn’t migrate out of state until mid-December), the Ring-billed and California Gulls (both of which are year-round residents), the Herring, Lesser Black-backed (and the Greater Black-backed, in lower numbers), and Iceland Gulls (all three-to-four of which can be found in Nebraska as early as the beginning of October). If you’re going birding for gulls not only in December, but in the later parts of the winter or during winter months in future years, we need only be concerned with the basic plumages and can rule out alternate plumages.

Next, in mixed flocks, we can take advantage of the close proximity of the individual gulls to compare and contrast the bird’s sizes. Adult gulls can range in size from the Little Gull’s 9.8-inch body length holding about 4.2 ounces of body weight to the Great Black-backed Gull’s 2.6 feet holding a whopping 3.9-pounds. That means that the largest gull species can be more than 3 times the length of the smallest, and almost 15 times as heavy.

Alright, alright, alright. You’ve invested ____ words into this post (or you’ve been skimming, no judgement) and we still haven’t name-dropped the stars of the show. “Enough of the tips and tricks! Give me the gulls!” Coming right up.

ROSS’S GULL

The Ross’s Gull is a small and beautiful gull. Once rarely seen outside the Arctic, Ross’s Gulls had not been sighted in the continental United States until 1975. Nowadays, there are sightings almost every year. Keep an eye out for this dove-like seabird taking food from the surface of the water or just below it. Its prey items may include insects, marine invertebrates, and small fish. In terms of its shape, the Ross’s Gull has long wings relative to its body length compared to other gulls. With a diamond-shaped tail, it is one of only two gulls without a rounded tail (the other being the Sabine’s Gull). If you are within earshot, listen for a squeaky squawk that resembles the sound of scraping a coin or your fingernail against the ridges of one of those plastic tilt-image cards found in kids’ cereal boxes in the 90’s. If you can narrow down its species, then it only becomes a matter of aging the bird.

Of the gulls the Ross’s Gull may resemble, the only species of concern in the area is Bonaparte’s Gull. If you see that a Gull with a dark spot behind its eye has wings that are both pale gray and tipped in black, you are looking at a wintering Bonaparte’s Gull. A Ross’s Gull’s wings are only tipped in black when their wings are still white, and the gray is limited to the back.

MEW GULL

Another species that passes through Nebraska is the Mew Gull. This medium-to-small gull is smaller than the Ring-billed Gull, measuring about 16-18 inches in length. Looking for them fluttering over the water to forage, picking up little bits of good off the water’s surface with their legs hanging beneath them and head down. Their diet largely consists of fish, insects, earthworms, and marine invertebrates, and their calls are shorter and squeakier than the typical gull call. Mnemonically, it may be helpful to liken the sound to the tiny “mews” of kittens.

In addition to being smaller in size than the Ring-billed Gull, the first-winter Mew Gull’s bill is also smaller than that of the second-winter Ring-billed Gull. Additionally, while the Mew Gull’s first basic plumage has a patch of gray on its back, its wings are still tan with white fringing while the Ring-billed Gull’s second basic plumage has its gray covering most of its wings and a white back instead.

Another potential misidentification to watch for is between these first-winter Mew Gulls and second-winter Herring Gulls. As with Ring-billed Gulls, Herring Gulls are larger and have a larger bill than Mew Gulls in any age. If you aren’t able to see two of these birds in the same place to compare their size, then look at the eye color of the bird. The eyes of the first-winter Mew Gull are dark while those of the second-winter Herring Gull are yellow.

GLAUCOUS GULL

The last, and perhaps most complex of our three featured birds is the Glaucous Gull. Even though its call is not as unique as the Ross’s or Mew Gulls’, this gull still has some distinctive behaviors. Look for a massive gull with pink legs. The only species larger than the Glaucous Gull is the Great Black-backed Gull, the only gull a Glaucous Gull won’t try to bully and dominate in mixed flocks. Otherwise, expect to see these gulls raising its wings and squawking aggressively before attacking other gulls. Like other large gulls, Glaucous gulls are notably omnivorous. Besides eating marine invertebrates and fish, Glaucous Gulls are known to include much carrion in their diet. When foraging over water, Glaucous Gulls are known to pick up the remains left behind by polar bears and even human activity.

The Glaucous Gull takes four years to reach its adult plumage. Overall, its juvenile plumage is mostly white with buff or pale brown markings, sporting dark eyes and a pinky bicolor bill with a dark tip instead of the yellow eyes and bill of the adult.

When it reaches its adult basic plumage, the Glaucous Gull is entirely white on the rump and tail, pale gray across the wings and back retaining its trailing white stripe, and white on the face and belly with brown smudging around the back of the head, trailing down the nape and around the throat. As adults, Glaucous Gulls also develop a red spot on their otherwise-yellow bills.

Okay, that was a lot. But don’t be discouraged—identifying gulls eludes some of even the most skilled and experienced birders. It can be tempting to rely on color pattern to make most of your bird-IDs, but gulls with multiple years of molt can really complicate the issue. Trying to identify gulls can be an opportunity to flex and lean on using the three other keys to bird identification. First, take note of the bird’s habitat. Are you observing this bird along a coastline, or near ice? Where are you geographically, and what birds can be found here at this time of the year? Second, consider the bird’s size and shape. How big is it compared to the birds around it? Are its wings much longer than its body, or does it have a distinct tail shape? Does its bill look small for its face, or does it seem heavy? Third, observe its behavior. How is it foraging? Can you tell what it is eating? How does it interact with other birds or with humans? Answering these questions can do so much to narrow down the possibilities and send you on your way to a more confident gull ID.

How experienced are you in gull identification? Are you a gifted gull-identifier? Or does identifying gulls feel too gargantuan a task to take on? If the former, what are your keys to gull identification? If the latter, hopefully this post could provide some insight. Send us your own tips and questions through our contact page. We would love to hear from you. Stay tuned for more migration alerts in the future!