"Adult in breeding plumage.--Head, neck, and upper back dark, glossy black; coverts on the carpal joint pure white; greater wing-coverts pearl-gray; secondaries darker, passing into slate-gray; primaries frosted with pearl-gray, which soon wears off the outer quills, leaving the webs sooty black, with a well-defined narrow whitish streak down the middle of the inner webs of the four outer primaries; shafts white; back and rump grayish black; upper tail-coverts and tail pure white; under parts deep black; vent white; flanks, under wing-coverts, and axillars black. Bill livid red; feet orange-red; webs of toes much indented. Length, 236; culmen, 28; wing, 208; tail, 79; tarsus, 19; middle toe with claw, 25. "Adult in autumn and winter plumage.--In the latter part of July, when the molt begins (in Europe), the bird is curiously parti-colored, the new feathers of the head, neck, and under parts being white and those of the back gray (paler than in Hydrochelidon nigra). Later, the under parts, including the under wing-coverts and axillars, become white, the crown and nape being merely mottled with black; but by the following April the black color has reappeared to a considerable extent, especially in the axillars. "Immature.--In birds which are not mature, though capable of breeding, the black of the under parts has a brownish tinge and the tail-feathers are pearl-gray, especially toward the tips. In winter like the adult. "Young.--Similar to the winter plumage of the somewhat immature bird, but much mottled with dark brown on the upper parts, and the tail-feathers slightly darker gray with a brownish tinge toward the tips; upper tail-coverts always white. "Nestling.--Ruddy fawn-color, mottled with black above, unspotted pale cinnamon-brown below." (Saunders.) "Observed and shot by us in Mindanao, where it was flying over the rice-fields." (Bourns and Worcester MS.) 77. HYDROCHELIDON HYBRIDA (Pallas). WHISKERED TERN. Sterna hybrida Pallas, Zoogr. Rosso-Asiat. (1811), 2, 338. Hydrochelidon hybrida Saunders, Cat. Birds Brit. Mus. (1896), 25, 10; Blanford, Fauna Brit. Ind. Bds. (1898), 4, 307, fig. 70 (head); Sharpe, Hand-List (1899), 1, 33; Oates, Cat. Birds' Eggs (1901), 1, 175; McGregor and Worcester, Hand-List (1906), 20. Luzon (Meyer, Murray, Whitehead, McGregor); Mindanao (Bourns & Worcester, Mearns); Palawan (Whitehead, Steere Exp.); Negros (Whitehead). Southwestern, central, and southern Europe to China, Malay Archipelago, Australia, Africa.