Genus ARDEOLA, Boie, 1822.
The Pond Herons, or, as they are often called by British ornithologists, Squacco Herons, are smaller than the true Herons and Egrets, and are somewhat intermediate in plumage between Egrets and Herons. The head, neck, and back are always coloured, but undergo a complete change of colour in the breeding-season ; the posterior half of the body, with the wings and tail, is white. The species are scarcely distinguishable in non-breeding plumage, though differing widely in their nuptial garb.
The feathers of the neck, back, and upper breast are elongate, and those of the last two decomposed in breeding-plumage ; a crest of elongate lanceolate feathers is only developed in the breeding-season. Both the neck and tarsi are shorter than in typical Herons ; the bill is stout, the culmen about equal to the middle toe and claw or to the tarsus; wings ample; tail short, of 12 feathers.
Four or five species are known, inhabiting the warmer parts of the Old World ; of these two occur within our area.
Key to the Species.
a. Wing about 8 in.; head and neck in breeding- plumage brownish……………………A. grayi, p. 393.
b. Wing about 9 in.; head and neck in breeding-plumage chestnut……………………A. bacchus, p. 394.