Transcript:

Today on Animal Fact Files we’re discussing the xeme. Technically, this bird is also known as Sabine’s gull, but I really wanted an excuse to talk about an animal whose name starts with x, so we're using that common name for this episode. The common name, xeme, comes from this bird's genius name: Xema– which, as far as is known, doesn't mean anything and was just a made up word when the gull was described back in 1819. The xeme is the only species classified in its genus. Although its forked tail may make it seem closely related to the swallow-tailed gull (Creagrus furcatus) of the Galapagos, genetic evidence suggests this bird's closest living relative is the ivory gull (Pagophila eburnea) which also lives in the high Arctic.

Xemes spend their summers on top of the world, literally. They have what is essentially a circumpolar distribution across the northern polar regions of the world. Here they nest on the edge of the water in marshlands, ponds, lakes, and brackish water estuaries. Their nests are built on the ground and may or may not have lining of grasses, twigs, feathers, and other various materials. The parents are monogamous over subsequent years, meeting up with one another after their migration from their wintering areas. They both incubate the 1-4 brown speckled olive colored eggs for approximately three weeks. The chicks may leave the nest within their first day of life, learning how to swim quickly, but often staying close to the nesting area while they grow in their flight feathers.

In many ways, these gulls are more like terns in their behavior and appearance. They're angular with their forked, swallow-like tail. Terns are often referred to as “swallows of the ocean.” Xemes are also on the smaller side of gull species reaching about a foot, 30 centimeters, long with a 32 inch, 81 centimeter, wingspan– although they are not the smallest living gull species. They also migrate massive distances from their Arctic breeding grounds. During the winter, xemes travel across the equator to two known areas in the southern hemisphere: one off the coast of Peru and the other off the coast of South Africa. Here, they spend most of their time at deep-water uprising currents that bring food to the water's surface.

During the winter, xemes spend most of their time miles away from shore out at sea. While they migrate, they may sometimes move inland to lakes and rivers where they can be observed on occasion, however, once they reach their wintering grounds, they're rarely seen from shore. They eat small fish, crustaceans, and other invertebrates carried by currents rising from the seafloor. They also follow whales, seals, and boats to gather the leftovers they leave behind. These gulls catch food by skimming the water's surface, although, back at their summer sites, they also stir up insects to catch them while flying or overturn rocks to see what's hiding beneath.

Predators to xemes include birds of prey such as peregrine falcons who may try to dive on flying adults– although most attempts at this end in failure. Their eggs and chicks are taken by other gulls, ravens, foxes, and even polar bears, but the adults employ a distraction strategy to keep them away. When a threat draws near, the parent xeme will feign an injury to draw the predator’s attention away from the nest; this is another trait that's relatively rare among gulls. The oldest recorded living xeme so far was just over 8 years old.

These gulls are pretty easy to tell apart from other seafaring birds in their range even though they often form large, mixed species flocks. In their breeding plumage, they have a dark grey head with black outlines. It's faded in the winter, with just the back of the head showing a grey speckling. The top of their wings is grey, although it's more brown and scale-like in juveniles. Their wings have a black triangle at the tips which, when connected with the grey back, forms a distinct M-shape in flight. Plus, adults have a two-toned bill with the base appearing black and the tip showing off a bright yellow hue. It takes two years for the juveniles to grow in full adult plumage.

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