The present family comprises but a single genus (Cochlearius) and two species, the oldest known being the South American Boat-bill (C. Cochlearius), which ranges from southern Brazil over Amazonia and Guiana to Colombia and Ecuador, and the Central American Boat-bill (C. Zeledoni), which occurs in suitable situations from Mexico to Panama. They are small Night Heron-like birds, sixteen and eighteen inches in length respectively, their most-marked character being the possession of an enormous bill which is greatly depressed and excessively dilated laterally, the lateral outlines being much bowed. The bill approximates three inches in length and nearly two inches in width, and suggests at once possible kinship with the African Shoe-bill, and the naked skin between the branches of the lower jaw is dilatable into a pouch or bag. As further characters it may be mentioned that the Boat-bills have four pairs of powder-down tracts, which serve to distinguish them from the Ardeidae, which possess but two or three pairs of such areas, while they agree with the latter in having the feather-tracts very narrow, and the inner edge of the middle claw distinctly pectinated. The possession of a long nuchal crest by the Boat-bills seems another mark of relationship with the Night Herons.
The plumage of the South American species is a delicate lavender-gray above, the upper mantle with a broad band of black extending a little way down its sides, the wing-quills hoary gray or whitish, and the lower back, rump, upper tail-coverts and tail hoary gray, while the crown and crest are blue-black, the forehead white, the sides of the face, throat, and chest white, becoming delicate lavender-gray along the sides, and the breast and abdomen dark cinnamon-rufous; the eyes are large and dark, the upper mandible dark brown, and the lower mandible clear yellow, while the feet are dull or dirty yellow. The Central American species (C. Zeledoni) is similar to the other except that it is larger, the general coloration much darker and browner, the crest much shorter, and has the throat and breast pale vinous or light tawny.
Notwithstanding the fact that the Boat-bills are very widely distributed and have been known to science for upward of one hundred and fifty years, comparatively little appears to have been recorded concerning their life history. They appear to associate in small flocks or colonies and to frequent the mangrove swamps, being apparently nocturnal in their habits. Thus Salvin records finding the more northern species on the Cays of British Honduras and in Guatemala, skulking in the mangroves, and Mr. C. C. Nutting found them in similar situations in Costa Rica, while Dr. Richmond observed several colonies on the Rio Frio,Costa Rica., Mr. E. A. Goldman, who has seen them at a number of points in Central America, regards the Boat-bill as a stupid,dull bird, permitting one to approach within a dozen or fifteen feet, and when taking wing only flying for a few yards to skulk among the tangled undergrowth. The note is described as a harsh croak or squawk. The nest and eggs appear to be unknown.
As already hinted, even the casual observer would doubtless be struck at once by the strong albeit somewhat superficial resemblance between the members of the present family and the great African Shoe-bill, the sole tenant of the succeeding family; but when the structural characters are compared it is found to be rather a case of “converging analogy ” than actual affinity. “At first sight,” says Dr. Stejneger, “the Cochlearius seems to represent a pygmy Balaeniceps, between the legs of which it can stand upright without bending its neck, but even the outward likeness between the two bills is, on nearer inspection, by no means so great as would appear at first sight.” Although Professor Parker argued for a distinct relationship between them, it is improbable that they could have been derived from a common ancestor, but on the other hand the points of agreement with the Night Heron (Nycticorax) are so numerous and important as to leave no doubt as to the direction we must look for affinity. In fact, some systematists, regarding the Boat-bill as merely a Night Heron with an exaggerated bill, decline to accord it more than subgeneric rank under Nycticorax, but as Mr. Ridgway has shown, it has become modified and specialized in so many ways and so important features, besides the bill and the consequent alteration of the skull, that it seems well entitled to separate family rank.
A very remarkable bird, indeed, is the great Shoe-bill, or Whale-head of the Upper White Nile, and well entitled to be ranked as the sole representative of a family. This bird is about four feet in height, with very long legs, rather short neck and large head, which is provided at the back with a short, bushy crest; but the most marked feature is the immense, broad, flattened bill. This bill, which is eight inches or more in length, is concave in profile, with a ridge down the center of the upper mandible, which is prolonged at the tip into a nail or hook. The wings are long and broad, with the third and fourth quills longest; the tail is rather short and composed of twelve feathers. The general color of the plumage is ashy gray above, the mantle, scapulars, and wing-coverts having a slight greenish gloss, and paler gray below, the feathers of the fore neck and breast each with a dark stripe along the center. The feet and legs are leaden black in color, and the iris sometimes pale yellowish or occasionally grayish white. But a single species (Balaeniceps rex) is known.
The systematic position of the Shoe-bill has given rise to considerable discussion, though now it is pretty generally agreed that its closest affinity is with the Herons, with which it agrees in having powder-down patches on the rump; bare loral spaces, the right lobe of the liver largest, and the caecum single. According to Parker, who was the first to describe the skeleton, “the nearest relations of Balaeniceps are the South American Boat-bill and the little South African Umbrette (Scopus umbrella),” though Beddard is of the opinion that it “requires further study before its exact position can be determined.”
According to Mr. John Petherick, who was one of the first to observe these remarkable birds in their native haunts, they are “seen in clusters of from a pair to perhaps one hundred together, mostly in the water, and when disturbed will fly low over its surface, and settle at no great distance ; but if frightened and fired at, they rise in flocks high up in the air, and, after hovering and wheeling around, will settle on the highest trees, and as long as their disturbers are near will not return to the water. Their roosting place at night is, to the best of my belief, on the ground. Their food principally is fish and water-snakes, which they have been seen by my men to catch and devour. They will also feed on the intestines of dead animals, the carcasses of which they easily rip open with the strong hook of the upper bill. The breeding time of the Balaeniceps is in the rainy season during the months of July and August, and the spot chosen is in the reeds or high grass immediately on the water’s edge, or on some small elevated and dry spots entirely surrounded by water. The birds before laying scrape a hole in the earth, in which, without any lining of grass or feathers, the female deposits her eggs. As many as a dozen eggs have been found in the same nest.” Mr. Petherick succeeded in hatching some of the eggs under fowls and reared the young, sending them alive to England.