Fam. I. Palamedeidae.–In this group the head is small and the neck long, while the ribs have no uncinate processes, an archaic feature only found elsewhere among Birds in Archaeopteryx. The bill is short and Fowl-like, with a blunt decurved tip, a covering of soft skin, and more or less of a cere; the tibiae are partly naked, the entirely reticulated metatarsi moderately long and fairly stout; the toes are elongated and have strong claws, but only rudimentary anterior webs; the wings are ample and somewhat rounded, with eleven primaries and about sixteen large secondaries; the tail has fourteen broad feathers in Palamedea and twelve in Chauna.[[106]] Very noticeable are the two sharp spurs on the carpal portion of each wing, of which the foremost is the biggest; while in the even distribution of the body-plumage this Family recalls the Ratitae and the Spheniscidae. The sexes are alike; the nestlings, where known, are clad in yellowish-brown and grey down, the wing-spurs being developed in the earliest stages.
The following account of the habits of Chauna cristata,[[107]] the Chajá or Chaka, must stand for those of the Family, in default of further details concerning the more northern forms. This striking species is a common resident in the swamps and brackish lagoons of Argentina, where the islands of the intricate morasses often hold flocks of more than a hundred individuals, the separate pairs being said to mate for life. The flight is slow, with powerful strokes of the wing, the birds being greatly addicted to soaring in spiral circles until they are hardly visible, and at times floating lazily upon the breeze. They rise noisily from the ground with laboured action, and are occasionally seen to perch in trees; but they are by nature waders which swim with considerable facility, and, when they do so, their bodies shew well above the water, owing no doubt to the same pneumaticity which causes a crackling noise to be heard when the skin is compressed. The food consists of succulent water-plants, seeds, clover, and so forth. The loud cry, uttered with the head thrown back when the performer is on the ground, may be heard at a distance of two miles, the male giving vent to a "cha-ha" and the female replying with a "cha-ha-li." The regular period for reproduction is the southern spring–September and October–but it is a remarkable fact that breeding takes place also in autumn and even winter; the nest being a massive structure of reeds and rushes slightly hollowed above, and standing some two feet high with its foundations in water, or, in exceptional cases, floating. This nest is placed in some narrow channel or near the side of a lagoon, and contains from four to six oval buffish-white eggs. The female rises silently when disturbed, nor do the parents usually attack an intruder; but wounded birds are dangerous to approach, and make good use of their sharp spurs. The voice of the young is a feeble chirp; they are often trained, as they grow up, to act as guardians to the poultry of their owners. The flesh is coarse and dark, with a duck-like flavour.
Palamedea cornuta, the Horned Screamer, found from Guiana, Venezuela, and Amazonia to Ecuador and Eastern Peru, is glossy black with an admixture of white on the crown, lesser wing-coverts, and carpal edge; greyish foreneck, white abdomen, brownish-grey bill, and ashy feet. The lores are feathered, and a long, slender, yellowish-white horn adorns the forehead. The female is said to have buff on the wing-coverts. Chauna chavaria (derbiana auctt.) occurs in Venezuela and Colombia; it is glossy slate-black with greyer head and occipital crest, white cheeks and throat, and a little white on the wing. The naked lores are pink, the bill and feet apparently red. C. cristata (chavaria auctt.) differs in being dark grey, with a black ring round the neck and whitish-grey cheeks and throat. This is the largest form, and is bigger than a Turkey; it ranges from South Brazil to Argentina, and shares with Cariama (p. [258]) the name of Crested Screamer.
Fig. 32.–Chajá. Chauna cristata. × ⅒.
Fam. II. The Sub-Order Anseres contains the single cosmopolitan Family Anatidae, with the Swans, Geese, and Ducks; where, in spite of many attempts at subdivision, the lines of demarcation cannot yet be finally determined. Count Salvadori, however, having lately propounded a carefully-elaborated arrangement,[[108]] I have adopted his Sub-families in the present volume, viz. (1) Merginae, (2) Merganettinae, (3) Erismaturinae, (4) Fuligulinae, (5) Anatinae, (6) Chenonettinae, (7) Anserinae, (8) Cereopsinae, (9) Plectropterinae, (10) Anseranatinae, and (11) Cygninae.
The skull is short and robust; while the neck is abnormally developed, with extra vertebrae, in the Swans, and is usually long, though less so in the Sea-Ducks; in the Merginae and some Fuligulinae the customary posterior notches in the sternum are converted into two complete fenestrae or apertures. The bill is almost entirely covered with a soft sensitive membrane, ending in a horny process termed the nail, the skin being warty in Anseranas and Chen rossi; Cereopsis has a large tumid cere; both sexes of Cygnus melanocoryphus and C. olor have a knob at the base of the culmen, as have the males of Plectropterus, Tadorna cornuta, and the domesticated form of Cycnopsis cycnoïdes; the same sex of Somateria spectabilis has the posterior portion of the maxilla spread into a disk; Oedemia has it considerably swollen even in the female; Cairina and Plectropterus have caruncles on the forehead; Sarcidiornis has a fleshy comb at the proximal extremity of the beak in the male; while Biziura has a dependent flap on the chin, and a small subgular pouch. The bill is usually broad and depressed, and may be sub-conical, as in many Geese; spatulate, as in Spatula and Malacorhynchus; or somewhat less dilated, as in Chaulelasmus, and so forth. There is a distinct hook at the tip in Mergus, Dendrocycna, and Aex; the culmen is concave in Marmaronetta and Stictonetta; the nail is bent inwards in the latter and Erismatura, while the maxilla may overlap the mandible, or the covering membrane may even hang over the latter, as in Malacorhynchus, Hymenolaemus, and to a less extent in Elasmonetta and Nesonetta. The length is very variable, but the thin elongated "sawbill" of Mergus, with its serrated edges, is especially remarkable. Most characteristic of the Family is the presence of highly-developed lamellae or transverse tooth-like processes on both maxilla and mandible, which are visible when the jaws are closed in many cases, and are comparable to the similar formations in Prion (Procellariidae) and the Phoenicopteridae. They act no doubt as a sifting apparatus, but may assist in nipping off herbage and gripping fish, the piscivorous Mergansers having them directed backwards. The metatarsus is normally short or moderate, though occasionally long, as in Plectropterus and Dendrocycna; it may be stout and roundish, as in Anser, or laterally compressed, as in Fuligula; and is usually reticulated with transverse scutellae in front, though wholly reticulated in the Cygninae, Anserinae, and Dendrocycna. The anterior toes are fully webbed, Anseranas and Cereopsis alone having the foot semi-palmated; the hallux is short and elevated–except in the former species, where it is long and incumbent–and possesses a broad membranous lobe in the Merginae, Merganettinae, Erismaturinae, and Fuligulinae, while a very narrow membrane may be observed in the Anatinae and Chenonettinae. The claws are as a rule small and curved, but are long and sharp in Anseranas, Dendrocycna, Nettopus, and Plectropterus. The wings vary considerably, but are usually ample and rather long, though short in Cosmonetta, Erismatura, and Tachyeres; the number of primaries is eleven, and of secondaries from fifteen to twenty-eight, a horny spur being developed on the pollex, or even on the index, in Plectropterus, Sarcidiornis, Chenalopex, and Merganetta. The tail is, generally speaking, short, and may be narrow and pointed, as in Anas, Dafila, and Harelda; in Aex, Querquedula, Tadorna, and so forth, it is rounded; in Chenalopex squarer; and in Sarcidiornis and Asarcornis more cuneate. In Tachyeres the two median rectrices are long and recurved, and in the males of Harelda and Dafila, they are inordinately produced; while all the feathers have spiny shafts and narrow webs in the Erismaturinae and Merganettinae. The number varies from twelve to twenty-four, with even more in Swans. In Eunetta the upper and under tail-coverts exceed the tail itself.
The formation and disposition of the trachea[[109]] are of great importance. Cygnus musicus, C. buccinator, C. bewicki, and C. columbianus have a peculiar cavity in the sternum, while the windpipe, entering in front of the clavicles, traverses and retraverses the swollen keel, which in old birds it penetrates to its furthest extremity, the direction being changed in the two last from vertical to horizontal. Anseranas shews a double loop in this organ,[[110]] and in the males of many Ducks an enlargement is found at its junction with the bronchial tubes, consisting of a round bony structure, termed the bulla ossea or "labyrinth." Similar structures have been noticed in Chenalopex, Dendrocycna, Chloëphaga, Plectropterus, and Sarcidiornis; and in the Fuligulinae they shew apertures with membranous coverings; Metopiana peposaca, Mergus merganser, M. serrator, Tadorna cornuta, Oedemia fusca, and (doubtfully) Oe. perspicillata are stated to have an additional bulb, but Oe. nigra has none. Clangula glaucion and the Merginae have a swelling in the middle of the trachea.
The headquarters of the Family are in the north, while Dr. Sclater's calculations,[[111]] though modified by subsequent discoveries, give a good idea of the distribution. He assigns as residents about seventy-seven species to the Northern Regions, forty-one to the Neotropical, twenty-nine to the Australian, twenty-two to the Ethiopian, and twelve to the Indian; twenty Geese out of thirty-three, seven Swans out of ten, and twenty-six Sea-Ducks out of thirty-one belonging to the first. Polynesia is especially poor.
The Anatidae are for the most part of similar habits, and frequent seas, lakes, rivers, and watery spots generally, being found to a great extent in winter on the shore, especially where mudflats are exposed by the ebbing tide, and beds of such food-plants as Zostera (grass-wrack) are uncovered. Large flocks, which include many migrants, are formed at that season, and in spring the ganders and drakes commonly collect into parties while the female is incubating, which she does during twenty-one to forty-two days. Later in summer the majority of the Family shed their quills simultaneously, and conceal themselves until again capable of flight, the males then becoming dull in colour for several weeks, and resembling the other sex.[[112]] Merganetta is found only on the torrents of the Andes; Hymenolaemus and Salvadorina being also residents on mountain streams. The noisy flight is extremely powerful, and much swifter than it appears, the wedge-shaped formation which Geese affect being especially noticeable; some forms, however, are practically flightless, such as Nesonetta and the adult Steamer-Duck (Tachyeres). All the Anatidae swim exceptionally well, diving being carried to its perfection in the marine Fuligulinae; while the partially-submerged position with erect tail when feeding is known to every one. The various Swans have a whooping, trumpet-like, or hissing note; that of Geese is a harsh cackle, a gaggling sound, a clang or a "honk." Ducks do not always quack, but have whistling or grating cries in addition. The usual food is vegetable, consisting of grass, Chara, Zostera, Ulva, and other plants; but Mergansers live chiefly on fish, and the bill of fare is varied by grain, pulse, berries, frogs, insect-larvae, worms, molluscs, and crustaceans. The nest is placed on the ground in thick herbage, or sometimes almost in the water; holes in banks, hollow trees, or even branches at a slight elevation being chosen in certain cases: it is composed of heather, grass, moss, leaves, or rarely seaweed and twigs, and is lined with down, added gradually from the parent's breast during incubation. The eggs, which vary in number from two (Biziura) to about a dozen, are smooth and hard-shelled, with a plain white, creamy, or green coloration, and are commonly covered when left. The young return for a time to the nest at night, and are carefully tended by the female, who is occasionally assisted by the male, especially in Swans. It is not certain how tree-building Ducks convey the nestlings to the water, though it has been stated that they are carried in the bill; but it is no uncommon sight to see ducklings and cygnets climb upon their mother's back and hide beneath her wings when danger threatens.