The Order Ciconiiformes is a somewhat unwieldy assemblage consisting mainly of Water-birds, which may be classed under the Sub-Orders Steganopodes, Ardeae, Ciconiae, and Phoenicopteri. Of these the first contains the Phaëthontidae or Tropic-birds, the Sulidae or Gannets, the Phalacrocoracidae or Cormorants and Darters, the Fregatidae or Frigate-birds, and the Pelecanidae or Pelicans; the second the Ardeidae or Herons and Bitterns, and the Scopidae with the Umbrette; the third the Ciconiidae or Storks and Wood-Ibises, and the Ibididae or true Ibises and Spoon-bills; while the fourth comprises the Phaenicopteridae or Flamingos, and the extinct genus Palaelodus, for which Dr. Gadow recognises a separate family Palaelodidae. Among these the greatest affinity to the Procellariiformes is exhibited by the Steganopodes, whereas the Phoenicopteri are so closely allied to the Anseriformes that not a few writers prefer to include them in that Order.
The Steganopodes are aquatic and chiefly marine birds, so far homogeneous in structure that the details may well be set forth in common; while in some points they bear a great resemblance to the Cathartidae.[[73]] Each Family contains a single genus, except the Phalacrocoracidae, where Phalacrocorax and Plotus may be considered the equivalents of Sub-families.
The sternum is long, especially in Sula, while the large head and short thick neck of Phaëthon and Fregata may be contrasted with the small head and remarkably long neck of Phalacrocorax, and still more of Plotus; Sula and Pelecanus being moderate in both respects. The bill, which is more or less compound, is long, pretty straight, and generally compressed: in Phaëthon and Sula it is strong, conical, and pointed; in Phalacrocorax either stout with a long hooked nail, or less robust with the hook at the tip shorter, the sides being scabrous; in Fregata similar, in Plotus slender and tapering, in Pelecanus weak, much flattened, hooked, and scaly. The maxilla is furrowed in Sula, Pelecanus, and Phalacrocorax, with the median part concave in the latter, while the cutting edges of both mandibles are serrated in Phaëthon, Sula, and Plotus. The legs are placed far back, especially in Phalacrocorax, the tibiae being partly bare in Phaëthon and Pelecanus, but feathered in the other forms, of which Fregata has the clothing continued to the toes. The metatarsus is short, stout, and compressed, that of Fregata being extremely abbreviated, as in the Spheniscidae; it is entirely covered with hexagonal scales, becoming almost reticulated behind, while the toes exhibit distinct transverse scutes in Phalacrocorax, and have a similar tendency elsewhere. The hallux, which is somewhat elevated in Phaëthon, is turned inwards or forwards, and is connected with the remaining toes by full webs, except in Fregata, where the membranes are excised to about half their extent; this unique "Steganopodous" foot giving the name to the whole group. The stout curved claws–weaker in Fregata–are of medium length, that of the middle digit being serrated on the inner side in the last named, Sula, and Phalacrocorax. The wings are long and pointed, reaching their maximum in Fregata, their minimum in Phalacrocorax, and having a very ample spread in Sula and Pelecanus. There are eleven primaries, and from fifteen to twenty-nine incurved secondaries, which may even exceed the former. In Pelecanus the short, broad, roundish tail consists of from eighteen to twenty-four soft acute rectrices, but in the remaining genera the feathers are strong and stiff, being particularly rigid in Phalacrocorax and Plotus: Phaëthon has sixteen, which are moderate and graduated, with a long filiform median pair in the adult; Sula and Phalacrocorax from twelve to fourteen in a more or less wedge-shaped formation; Fregata twelve, arranged in a fork; while Plotus has the same number, forming a fan, the webs being very broad and showing curious transverse corrugations in mature birds, found also on the scapulars. The tail is fairly long in the four last mentioned, except in some members of Phalacrocorax. The V-shaped furcula ancyloses with the sternum in some of the Sub-Order, but Fregata differs from all other ornithic forms in the fact that the furcula also coalesces with the coracoids at its extremities, while the coracoids again unite firmly with the scapula, producing an almost rigid framework, considered by Professor Newton to be connected with the power which the bird possesses of sustaining itself nearly motionless in the air.[[74]] The peculiar angular articulation of the long eighth cervical vertebra in Plotus, which causes the Z-shaped "kink" in the neck, must also be noticed here.[[75]] The tongue is rudimentary; the nostrils are pervious in Phaëthon, impervious elsewhere, being practically obliterated in adults; the syrinx is tracheo-bronchial, except in Sula and Pelecanus, where the usual muscles are entirely absent. The subcutaneous air-cells of Sula are most remarkable. The newly-hatched young are blind and helpless, being naked and covered with blackish skin in Sula, Phalacrocorax, Plotus, and Pelecanus, though they soon acquire a white downy coat; in Phaëthon and Fregata they are similarly clothed on breaking the shell. The down of the adults is uniformly distributed, the aftershaft is diminutive or wanting. The gular sacs, horny excrescences on the beak, crests, and so forth, are noted below.
Fam. I. Phaethontidae.–Phaëthon aethereus, P. flavirostris, and P. rubricauda are chiefly found in the tropical regions of the south; but the first two species breed about as far north as the tropic of Cancer, while they frequent the West Indies, and occasionally stray to the Eastern United States, or even Newfoundland.[[76]] The third inhabits the southern seas and the Indian Ocean. All these Tropic- or Boatswain-birds, as they are denominated, have satin-like white plumage–often with a tinge of pink–varied by blackish bars or patches above, and black marks near the eye; the bill is red, or in P. flavirostris yellow, the metatarsi yellowish and the toes chiefly black. In P. rubricauda the long stiff median rectrices are dull red with black shafts and very narrow webs, in P. flavirostris they are pinkish with similar shafts, and in P. aethereus entirely white. The sexes are alike, the young being more irregularly marked and having no long tail-feathers.
The members of this Family are true denizens of the ocean, often met with many hundred miles from land; they will then hover constantly about a vessel, or even alight fearlessly on the rigging. They traverse the air with rapid sweeping flight, accompanied by constant quick pulsations of the wings; at one time soaring aloft to wheel in circles, at another plunging into the water from an immense height, though appearing again in a moment to float upon the surface. Their gait on land is shuffling, while they can hardly rise from level ground; the note is a harsh croak or chatter; the food consists of fish, squids, and other produce of the sea. No nest is made, but a single reddish-brown or buff egg, with spots and frecklings of red-brown, purplish or grey, is deposited in a hole or crevice in a cliff, among rocks, or even in a cavity in a rotten tree, both sexes assisting in incubation.[[77]] The parents sit very closely, screaming, pecking, and snapping when disturbed; in some places they are habitually caught while breeding, and deprived of the long tail-feathers, which are used for decorations.
Fig. 20.–Tropic Bird. Phaëthon aethereus. × ⅛.
Fam. II. Sulidae.–Sula bassana, the Gannet or Solan Goose, which nests at several stations off the west of Great Britain, in Ireland, and on the well-known Bass Rock, extends thence to Iceland, and down the American coast to Nova Scotia, while it strays to Greenland, and in winter reaches the Gulf of Mexico and northern Africa. The plumage is white, with a buff tinge on the head and neck, and black primaries; the bill is whitish, the feet dusky, and the naked skin round the eye and down the centre of the throat blackish-blue. S. capensis of South Africa and S. serrator of Australia are similar to the above, but the former has the rectrices black, the latter the four median feathers blackish-brown.
Fig. 21.–Gannet. Sula bassana. × ⅐.