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Gulls of all sorts, about 50 “species”, if laid out next to each other on a very long table, species after species, would pretty much grade from very white to nearly a complete dusky brown. In addition there are a few that have lots of really ebony black feathers. These black feathers are in a very similar pattern to the gray feathers we see on another swath of gulls. In other words they are an evolutionary work in progress; similar, different, overlapping, developing, adapting. They can be seen to have similar relatives and many share similar feather patterns from group to group, but vary in size, geography, and specific features (like the size and coloration of the bill, legs, or eyes). They are all gulls and there is no mistaking that – but they are all different in a kaleidoscope of ways.
Avian taxonomists work to combine and/or separate the, often similar looking populations. The recent ice ages created geographic populations separated from their relatives by many thousands of years of intrusive ice. Tongues of glacial ice separated populations as tundra and mountain were inundated and icy fissures created. When the ice melted back they didn’t share the same looks or language – they had adapted to their new home and its requirements. They are a hardy group with a greater number of species (or types) north of the equator than are found south of it. But they are found all over the world including the South Pacific, Australasia, New Zealand, South America, and Antarctica. There are more types north of the equator; most likely because the Northern Hemisphere has more land and the glacial epochs divided it into more separate parcels than were seen in the Southern Hemisphere.
I am going to insert a whole gaggle of images that are mostly North American in origin. However, the birds are not so neatly arranged in real life. The birds of northern Canada can overlap with and often breed with populations in Kamchatka and Siberia to the west and Iceland and Scotland to the east. In general, gull populations have a breeding fidelity to specific sites and geography; but they can fly and are strong flyers. Hence there can be unexpected gulls found here and there at any given moment. I will try to arrange them by size, coloration, and closest relatives but that may not be a perfect approach or even doable. Enjoy them, appreciate them and marvel at the skills and adaptations they have developed during the last several hundreds of thousand years. They are pretty cool despite the cultural denigration we assign them, mostly because they are opportunistic feeders and we find them in landfills, trash tips, and dumps as well as fast-food parking lots. For the most part they are hardy and hard working. Oh, by the way the term “sea gull” is meaningless. Many of the gull types are ocean going and live along the edge of salty water, but there are many fresh water gulls and some that are much happier in the prairie-lands than they are at the beach. They are mostly tied to the water but it isn’t a requirement nor is it universal. Also, like many animals, the breeding and wintering habitats are not always similar.
When you go out looking at gulls note the feather color and pattern, compare the size to other common birds, look at the bill and its size, pattern and color, note the time of year as things change in breeding season, look at the eye color, and especially the leg color. Now let’s take a look at a few of our gulls.
These are representative gulls of the northern hemisphere. In the south there are fewer species, but they also range in size from smallish (like Australia’s Silver Gull and New Zealand’s Red- and Black-billed gulls). They are hardy, bright, and opportunistic. they have been marvelously successful over the past few million years and they offer us a look at speciation/evolution in action. All in all they are much cooler than we usually credit them.