In the Larinae the strong, horny bill is of moderate length, though exceptionally small in Rhodostethia, the maxilla being curved, but hardly hooked; in the Stercorariinae there is a distinct hook, and the base is covered by a cere, said to be hard or soft according to the season, and possibly, shed after the manner of certain Auks.[[197]] In the Sterninae the beak is nearly straight and pointed, while comparatively slender; in the Rhynchopinae, the maxilla, which moves vertically with ease, is much shorter than the mandible, and both are compressed anteriorly until they resemble truncated knife blades. The tibia is generally partly bare; the metatarsus is fairly long in the first two Sub-families, and is scutellated in front, being usually smooth behind, though rougher in Pagophila; the anterior toes are fully webbed, with claws which vary from weak to moderate, or even to strong and hooked, as in the Stercorariinae. The elevated hallux is joined by a membrane to the inner toe in Leucophaeus, and is rudimentary or absent in Rissa. In the Sterninae and Rhynchopinae the metatarsus is short–especially in the latter, where the web between the inner and middle digits is deeply incised, as are both webs in Hydrochelidon and Gygis; the claws are long, slender, and curved. The pointed wings, excessively lengthened in the two last-mentioned Sub-families, have eleven primaries, of which the outer is particularly small, and from fifteen to twenty-three secondaries. The tail may be nearly even as in Larus, deeply forked as in Sterna generally, less excised as in Xema, Hydrochelidon, Naenia, and Rhynchops, graduated or cuneate as in Rhodostethia, Anous, and Gygis; all the twelve feathers being rounded or acute: in the Stercorariinae the two central rectrices project beyond the others, being decidedly pointed in Stercorarius crepidatus and S. parasiticus, but rounded and twisted in the shaft until the webs are vertical in S. pomatorhinus. The furcula is U-shaped, the syrinx tracheo-bronchial, the tongue lanceolate, the nostrils are pervious; an after-shaft is present, while both adults and young have abundant down, that of the latter commonly shewing a mixture of white, with grey, yellowish, slaty, or brown. Naenia has elongated plumes at the gape, and a few Terns have slight nuchal crests.
Gulls and Skuas are widely-ranging and essentially marine birds, even those species which nest inland being commonly observed near salt water, and seeking the coast when incubation is over. They are always inclined to be gregarious, and are more or less resident in Britain, but the undoubted influx of birds from abroad in autumn makes it difficult, or even impossible, to determine their exact status in every case. Their untiring and easy flight is only second to that of the larger Petrels; the majestic style of the Great Black-backed Gull, and other forms, being a great contrast to the wavering but graceful movements of the Kittiwake or Bonaparte's Gull. All walk well, though sedately, swim to perfection, and rise easily both from land and water, usually breaking into a run before taking to the wing from the ground; while they almost invariably alight with uplifted pinions. The wild characteristic note varies less than in most large groups, that of the bigger species being harsh and querulous, that of the smaller laughing or screaming; the lesser Skuas give vent to a curious mewing cry, and the Great Skuas to a similar but deeper sound. At the breeding-quarters the utterances are naturally more agitated and shrill, and the parents hang excitedly above a visitor's head. The food consists mainly of fish, molluscs, crustaceans, and worms, but is varied in the stronger forms by small mammals, young birds, and eggs: the Great Black-backed Gull undoubtedly attacks lambs and weakly ewes; carrion is not uncommonly devoured; and Larus maculipennis acts as a scavenger at Buenos Aires, besides clearing the country of grasshoppers, and robbing the Cayenne Lapwing of its insect booty. Skuas give chase to their smaller kin, and force them to disgorge the fishes they have just caught, while even Solan Geese are sometimes victimized; Larus scopulinus, moreover, which robs the Oyster-catcher of New Zealand, is a further instance of parasitic habits. Insects and their larvae, turnips, berries, and grain are also eaten by these omnivorous but useful creatures. Their main sustenance is naturally derived from the ocean, or its oozy shores; but flocks are commonly seen on pastures and arable lands near the beach, or following the plough further from the sea, though not being of the species which breed in the interior, nor driven inland by stress of weather. At times Gulls almost, if not quite, disappear below the water when swooping on their prey, and Kittiwakes have been said to pursue it beneath the surface. A common habit is that of preening and washing the plumage in company at favoured spots, while one that is less well-known is that of casting up the indigestible parts of the food in pellets, as do many other birds. The nesting sites are very frequently precipitous rocks and stony islands, but inland marshes and lakes accommodate many species, while in certain localities trees as high as thirty feet are selected. Skuas breed on moors or hills near the sea in Scotland, on the fells of Scandinavia, and on the tundras and barren grounds of the Arctic Regions, the nest being a mere depression in the herbage or moss; the remainder of the tribe generally collect a mass of grass, moss, flags, sedges, heather, twigs, or sea-weed, though a mere hollow in the soil or sand often serves their purpose. The eggs vary in number from two in the case of the Ivory Gull and the Skuas to three or exceptionally four; they are brown, drab, or green, with blotches and spots of brown, black, grey, and lilac, and recall those of Plovers. Both sexes have been said to incubate in Larus minutus and Rissa brevirostris; the young are comparatively helpless for a few hours or perhaps days, and are at first fed by the parents.
Terns resemble Gulls in many of their habits, but are more cosmopolitan, and decidedly migratory in Britain; they are essentially marine, yet some species breed on inland waters in summer. Particularly slender and graceful, these long-winged birds may usually be distinguished by their irregular or hovering flight, and are known as Sea-swallows; while their method of beating up and down maritime streams or shallows, singly or in pairs, in search of fish, is quite peculiar to themselves. At such times they make constant plunges into the water, often completely immersing their bodies, or occasionally discontinue their operations to engage in trivial and seemingly amicable quarrels. The note, though hoarse in some cases, is usually a squealing or grating sound, the latter especially when disturbed; the food consists of fish and crustaceans, insects–said to be sometimes taken on the wing–frogs, newts, locusts, grasshoppers, caterpillars, leeches, molluscs, and medusae. Terns are wary but bold, commonly circling around a wounded companion until several are shot; the Noddies (Anous), however, are much more sluggish and silent. On the ground all move with comparative ease. The nest of Hydrochelidon is a mass of water-weeds placed on some tussock in a wet inland swamp; that of Anous, when situated on trees, bushes, or rocky ledges, is composed of twigs, sea-weed, and like materials; but most species merely make a hole in the sand or soil, with little or no lining. Depressions on level rocks, the surface of prostrate plants, and heathery, grassy, or muddy flats are often utilized as alternatives, while colonies are usually formed. Two or three olive, reddish-brown, green, or stone-coloured eggs, with blotches, spots, scrawls, or oblique streaks of black, brown, grey, or lilac, are deposited; the Noddy and Sooty Terns, however, have a single white egg with red markings, and Gygis one, which is buff, marbled, spotted, or often scrolled with brown and grey, and is laid on any slight cavity of a branch, a broad leaf-stalk, or a coral reef. The nesting habits of Naenia are unknown, but it frequents rocky, cavernous shores.
Rhynchops has a peculiarly low flight, rapid and gliding, with many a turn and twist, which has gained it the name of Skimmer. The food, often sought towards evening, appears to consist of small fish and crustaceans; it is procured by keeping the bill wide open, with the long mandible ploughing through the water or mud, and leaving a distinct furrow in its track. The cry is a low harsh scream or shrill twittering note. A hollow in some sandy river-bank or island serves to contain the three or four grey, green, buff, or white eggs, with blotches and streaks of purplish-grey and dark brown. The female is said to sit only at night or in stormy weather, and the young to be unable to fly for several weeks,[[198]] but the remaining habits resemble those of Terns.
The sexes in the Laridae are invariably similar, the plumage being grey and white, or more rarely blackish or brown, details of which will be found below. The young are duller, being mottled with brown or black in immature Gulls. The frequent black or brown heads, often lacking at certain ages or times of year, the seasonal changes generally, the neck-collar of Xema sabinii and Rhodostethia, and the rosy tint on the breast in the latter species, Larus franklini, and Sterna dougalli may be noticed in passing. The members of the Family range in size from the Glaucous to the Little Gull; the largest Tern being the Caspian, and the smallest, as its name indicates, the Least Tern.
Sub-fam. 1. Stercorariinae.–Of this widely spread but curiously distributed group, Megalestris catarrhactes, the Great Skua or Bonxie, a fine rufous-brown species, with a white wing-patch which is very conspicuous in flight, breeds in Shetland, the Färoes, Iceland, and possibly north of Hudson Strait, occurring in South Greenland and Norway, and reaching New England and Gibraltar in winter. It nests in colonies, though each pair occupies a distinct area, which the parents defend with exceptional boldness, swooping down swiftly with a heavy rush, and dropping the feet when at close quarters, as if to strike an intruder. Unlike their smaller kin, which will attack a man from any side and hit him with their wings, these birds commonly aim directly at the face, and their onslaught, if not averted, is really dangerous, while they only just clear the head when threatened with a stick. The two eggs, deposited in a depression in the herbage, are dull brown or greenish, with somewhat indistinct umber markings. The food consists chiefly of fish, which the smaller Gulls are forced to disgorge, while Kittiwakes and the like are themselves occasionally devoured in default of other prey. M. chilensis, spotted with chestnut above, and more rufous below, occupies America south of Rio de Janeiro and Callao; the sooty-brown M. antarctica–the stouter-billed Port Egmont or Sea Hen–replacing it from the Falklands to the Australian and New Zealand seas, and reaching northwards to the Comoros and Madagascar. In the Antarctic Victoria Land occurs a paler form, M. maccormicki.
Stercorarius pomatorhinus, the Pomatorhine Skua, breeds on the tundras of Siberia and possibly from Greenland to Bering Sea, migrating to Britain and as far as South Africa, North Australia, and Peru. The plumage is brown, with blacker head and gorget, white breast, and acuminate white neck-feathers tipped with yellow. The projecting median rectrices with their vertically twisted vanes are mentioned above (p. [301]). Uniform brown specimens may be immature. S. crepidatus, the Arctic Skua, is smaller, and nests as far south as Northern and Western Scotland, but properly occupies Arctic and sub-Arctic Europe, Asia, and America; in winter, it reaches South Africa, Australia, New Zealand, and Brazil. The elongated rectrices are not twisted, but are pointed, while a uniform dark phase–the true S. richardsoni–is common to both sexes. S. parasiticus, Buffon's Skua, distinguished from the last-named by its extremely prolonged rectrices and greyer upper surface, breeds on the Scandinavian fells and throughout the Arctic tundras and barren grounds, migrating as far south as Gibraltar and lat. 40° N. in America. The habits of the members of this genus are similar to those of Megalestris, but their quicker flight enables them to rob even Terns, and the mewing cry is most peculiar, while the eggs are intermediate in style between those of Whimbrels and Gulls. These small Skuas often destroy Lemmings.
Sub-fam. 2. Larinae.–Rissa tridactyla, the Kittiwake, breeds from the circumpolar regions southwards to the Kuril Islands, the Gulf of St. Lawrence, and North-West France; in winter it reaches western North America, the Bermudas, the Canaries, the Mediterranean, and the Caspian. The feet are black, the hind-toe is absent or rudimentary. From Larus canus, which it closely resembles when flying, it can be distinguished by the absence of white spots at the ends of the primaries. The young bird, or Tarrock, is much variegated with dark grey or black, and has a blackish tip to the tail, as is the case in most fresh-water Gulls. Many fine colonies inhabit the loftier cliffs of Great Britain, the nests of sea-weed and grass being closely crowded together, and the eggs exhibiting softer colours than is usual in the Sub-family. The darker R. brevirostris of Bering Sea has red feet.
Pagophila eburnea, the Ivory Gull, seems truly circumpolar, while it accidentally visits Britain, Northern Europe, and New Brunswick. It is pure white, with black feet, the young shewing grey and black variations. It will eat whale- or seal-offal.
Leucophaeus scoresbii, of South Patagonia, the Falkland Islands, and the neighbouring Antarctic seas, has a crimson bill, coarse red feet, with somewhat excised webs, a dark hood in immature examples, and a white tail. Gabianus pacificus of Australia and Tasmania is somewhat like Larus marinus, but has a very short stout bill and a black-banded tail.