HYDROCHELIDON. 87 
“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. 
“Tmmature.—In birds which are not mature, though capable of breed- 
ing, 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; OarEs, Cat. Birds’ Eggs (1901), 1, 
175; McGregor and WorcEsTER, Hand-List (1906), 20. 
Luzon (Meyer, Murray, Whitehead, McGregor) ; Mindanao (Bourns & Worces- 
ter, Mearns) ; Palawan (Whitehead, Steere Exp.) ; Negros (Whitehead). South- 
western, central, and southern Europe to China, Malay Archipelago, Australia, 
Africa. 
“Adult male in breeding plumage.—Forehead, crown, and nape deep 
black ; from the gape to the nape a conspicuous white streak ; upper parts 
slate-gray, darker on the primaries, except when these are new and 
frosted ; shafts white ; inner webs of outer pairs of primaries white on the 
