The Forster Tern 



No. 286 



Forster's Tern 



A. 0. U. No. 69. Sterna forsteri Nuttall. 



Description. — Adult in summer: Top of head and nape sooty black; rump 

 white, shading on upper tail-coverts; remaining upperparts pale pearl-gray; wing- 

 quills dusky, heavily overlaid to tips with silvery gray, with ivory shafts, and with 

 white (decreasing inwardly) on the inner webs; tail the color of back, deeply forked, 

 the outer pair of feathers much elongated and tapering, reaching beyond the tip of the 

 folded wing; their inner webs of a much darker gray than the narrow outer webs; underparts 

 white; bill dull orange basally, the terminal half, or at least third, blackish; feet orange- 

 red. Adult in winter: Similar, but black cap wanting, represented only by broad 

 black stripe on side of head (including eye), and by grayish tinge of hind-head and 

 nape; tail shorter and not so deeply forked, the outer feathers broader and less tapering. 

 Bill duller, the dusky tip scarcely contrasting; feet dull reddish. Previous to renewal 

 i n the autumnal moult, most specimens have completely worn off the silver "plating" 

 of the outer primaries; leaving them brownish dusky. Young: Like adult in winter, 

 but upperparts extensively varied by or overlaid with light brownish; tail shorter, its 

 feathers becoming dusky terminally. Length 355.6-406.4 (14.00-16.00); wing 254 

 (10.00); tail, the central feathers, 71. 1 (2.80), the lateral pair 171. 5-190.5 (6.75-7.50); 

 bill 38.1 (1.50); depth at base 10.2 (.40); tarsus 24.9 (.98). 



Recognition Marks. — Size of Common Tern; distinguishable from it by subtle 

 but sure marks; the bill is stouter and more extensively black on terminal portion; 

 the upper tail-coverts are grayer; the tail more deeply forked, and the outer pair of 

 feathers dark on inner webs. 



Nesting. — Nest: In scattered colonies, in marsh on low or partially inundated 

 ground; a shallow, broad-skirted crater of interlaced grasses or sedges plucked green, 

 occasionally of assorted drift materials. Eggs: 2 or 3; ovate; variable as to ground, 

 greenish, olive-buff or pinkish olive-buff to dark olive-buff, yellowish glaucous, dull 

 chamois, etc., handsomely spotted or blotched with black or brownish black, or with 

 sepia self-tones and mold gray undershell markings. Av. of 12 sets in the M. C. O. 

 coll.: 42.7 x 30 (1.67 x 1. 18); index 71. Season: c. June 1st; one brood. 



General Range. — North America. Breeds in the interior from northern 

 Washington, Saskatchewan, and Manitoba, south to central California, Nevada, 

 northern Colorado, northeastern Illinois, etc., and along the Atlantic and Gulf Coasts, 

 locally, from New Jersey to Texas. Winters from the South Carolina and the Gulf 

 Coast south to Guatemala and from southern California to Oaxaca. 



Distribution in California. — Abundant spring and fall migrant especially 

 coastwise. Breeds sparingly in suitable localities both east and west of the Sierras 

 south at least to Los Banos (eggs taken May 23, 1914). Winters sparingly along the 

 coast in the San Diegan district, and casually north to Stockton and Santa Cruz. 



Authorities. — Lawrence {Sterna forsteri), in Baird, Rep. Pac. R. R. Surv., vol. 

 ix., 1858, p. 862 (Sacramento Valley); Ray, Condor, vol. v., 1903, p. 47 (Lake Tahoe, 

 breeding; desc. nest and eggs); Willett, Pac. Coast Avifauna, no. 7, 1912, p. 16 (status 

 in s. Calif.); McAtee, U. S. Dept. Agric. Farmers' Bull. 497, 1912, p. 22 (food). 



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