Fam. 3. Totipalmatae, characterised by having the hinder toe or hallux more or less directed inwards, and united to the innermost of the anterior toes by a membrane (fig. 332, A). In this family are the Pelicans, Cormorants, Gannets, Frigate-birds, Darters, and others. They all fly well, and have short legs, and amongst them are almost the only Natatorial Birds which ever perch upon trees.
The Pelicans (Pelicanidae) are large birds, which subsist on fish, and are found in Europe, Asia, Africa, and the New World. They sometimes measure as much as from ten to fifteen feet between the tips of the wings, and most of the bones are pneumatic, so that the skeleton is extremely light. The lower mandible is composed of two flexible branches which serve for the support of a large "gular" pouch, formed by the loose unfeathered skin of the neck. The fish captured by the bird are temporarily deposited in this pouch, and the parent birds feed their young out of it. The bill is long and straight, and the upper mandible is strongly hooked at the tip.
In the Cormorants (Phalacrocorax) there is no pouch beneath the lower mandible, but the skin of the throat is very lax and distensible; the nail of the middle toe is serrated. They are widely distributed over the world, one species being very abundant in many parts of Europe. The Gannets (Sula) have a compressed bill, the margins of which are finely crenate or toothed. They occur abundantly on many parts of the coasts of northern Europe, one of the most noted of their stations being the Bass Rock at the mouth of the Firth of Forth. Another species (Sula variegata) is of greater importance to man, as being one of the birds from the accumulated droppings of which guano is derived. The Frigate-birds (Tachypetes) are chiefly remarkable for their extraordinary powers of flight, conditioned by their enormously long and powerful wings and long forked tail. They occur on the coasts of tropical America, and are often found at immense distances from any land. The Tropic-birds (Phaeton) inhabit intertropical regions, and are found far out at sea. They have short feeble feet, and long pointed wings.
The Darters or Snake-birds (Plotus) are somewhat aberrant members of this group, characterised by their elongated necks and long pointed bills. They occur in America, Africa, and Australia, and catch fish by suddenly darting upon them from above.
Fam. 4. Lamellirostres. - The last family of the Natatores is that of the Lamellirostres, including the Ducks, Geese, Swans, and Flamingoes, and characterised by the form of the beak (figs. 332 and 334), which is flattened in form and covered with a soft skin. The edges of the bill are further furnished with a series of transverse plates or lamellae, which form a kind of fringe or "strainer," by means of which these birds sift the mud in which they habitually seek their food. The bill is richly supplied with filaments of the fifth nerve, and doubtless serves as an efficient organ of touch. The feet are furnished with four toes, of which three are turned forwards, and are webbed, whilst the fourth is turned backwards, and is free. The trachea in the males is often enlarged or twisted in its lower part, and co-operates in the production of the peculiar clanging note of most of these birds. The body is heavy, and the wings only moderately developed.
Fig. 334. - A, Head of the Grey Lag Goose; B, Foot of the domestic Goose.
The groups of the Ducks (Anatidae), Geese (Anserinae), and Swans (Cygnidae) are too familiar to require much special notice. The Anatidae, or true Ducks, have the hallux furnished with a very narrow membranous lobe, and the laminae of the upper mandible generally projecting. As examples may be taken the Mallards and Teals (Boschas), the Widgeons (Mareca), the Shoveller (Anas), and the Pin-tail Ducks (Dafild). The Sea-ducks (Fuligulinae) frequent the sea chiefly, and have the hallux furnished with a wide membranous lobe. Good examples are the Eider-duck (Somateria), the Surf-duck (Oidemia), the Canvass-back Duck and Pochard (Fuligula), and the Golden-eye (C/angula).
The Anserinae are distinguished from the Ducks chiefly by their stronger and longer legs, and comparatively shorter wings. Good examples are the Grey Lag (Anser ferns), the Canada Goose (A. canadensis), the Bean-goose (A. segetum), and the Snow-goose (A. hyperboreus). All the domesticated varieties of Geese appear to be undoubtedly descended from the "Grey Lag" Goose, a common wild species which is found in marshy districts in Europe generally, in Northern Africa, and as far east as Persia.
In the Swans the neck is extremely long, and the legs are short. In the Hooper Swan (Cygnus ferns) the sternal keel is double, and forms a cavity for the reception of a convoluted portion of the trachea. This is not the case, however, with the Mute Swan (C. olor), the Black Swan (C. atratus), or the Trumpeter Swan (C buccinator), all well-known members of the group.
The Flamingoes, however, forming the group of the Phoenicop-teridae, require some notice, if only for the fact that the legs are so long and slender that they have often been placed in the order Grallatores on this account. The three anterior toes, however, are webbed or completely united by membrane, and the bill is lamellate, so that there can be little hesitation in leaving the Flamingo in its present position amongst the Nata-tores. The bill is singularly bent, both mandibles being suddenly curved downwards from the middle. The common Flamingo (Phoenicopterus ruber) occurs abundantly in various parts of southern Europe. It stands between three and four feet in height, the general plumage being rose-coloured, the wing-coverts red, and the quill-feathers of the wings black. The tongue is fleshy, and one of the extravagances of the Romans during the later period of the Empire was to have dishes composed solely of Flamingoes' tongues. Other species occur in South America and Africa.
As regards the distribution of the Natatores in time, the earliest traces of the order are found in the Cretaceous rocks. In deposits of this age in the United States, Professor Marsh has exhumed the bones of several forms (Graculavus and Laornis); and other forms (Cimolornis) have been described from the Cretaceous of Europe. In the Eocene Tertiary are found several Natatorial birds, the most interesting of which are the Gastornis Parisiensis and Agtiopterus of the Paris basin, the former being apparently a huge and wingless goose, whilst the latter is allied to the Flamingoes. Under this order also probably comes the extraordinary fossil bird, recently described by Professor Owen, from the London Clay (Eocene) of Sheppey under the name of Odontopteryx toliapicus. In this singular bird (fig. 335) the alveolar margins of both jaws are furnished with tooth-like denticulations, which differ from true teeth in being actually parts of the osseous substance of the jaw itself, with which they are continuous. They are of triangular or compressed conical form, and are of two sizes, the larger ones resembling canines. From the consideration of all the discovered remains of this bird, Professor Owen concludes that "Odontopteryx was a warm - blooded feathered biped, with wings; and further, that it was web-footed and a fish-eater, and that in the catching of its slippery prey it was assisted by this Pterosauroid armature of its jaws." Upon the whole, Odontopteryx would appear to be most nearly allied to the Anatidae, but the denticulation of its jaws is an entirely unique character.
Fig. 335. - Skull of Odontopteryx toliapicus, restored. (After Owen.)
Leaving the Eocene, the Miocene and later Tertiary deposits have yielded the remains of numerous Swimming Birds, as has also the Post-tertiary; but no special interest attaches to any of these, unless the great Cnemiornis of the Quaternary of New Zealand be rightly referred here, since this has the peculiarity of having been unable to fly.