304 Field Museum of Natural History — Zoology, Vol. IX. 



Adult in summer: Bill, yellow, tipped with black; forehead, white; 

 crown and lores, black; upper parts, pearl gray; under parts, white; 



outer primaries, brownish black on outer 

 webs and inner half of inner webs; tail, 

 white; feet orange, yellow. 



Adult in winter: Forepart of crown, 

 white, marked with black; occiput, 

 black. Immature birds have the upper 

 parts mottled with buff and the bill 

 dark brown. 

 Least Tern. Length, 9. 50; wing, 7; tail, 3.50; 



tarsus, .60; bill, 1.20. 

 Although this species occurs on Lake Michigan, and occasionally 

 on the inland waters of Illinois and Wisconsin, it is apparently by no 

 means common. "Occurs in summer, nearly throughout the Missis- 

 sippi Valley." (Ridgway.) "A very rare summer visitant in this 

 vicinity. -'■= * * * A fine male specimen is in the collection of the 

 Chicago Academy of Sciences, obtained June 11, 1876, upon the Calu- 

 met marshes." (Nelson, Birds of N. E. 111., 1876, p. 149.) "Chiefly 

 coastwise but passes up the Mississippi Valley to Dakota and Minne- 

 sota; breeds abundantly along the Gulf coast in Louisiana and Texas, 

 also in the interior; known to breed in Kansas and Dakota." (W. 

 W. Cooke, Bird Migration Mississippi Valley, 1888, p. 58.) Kumlien 

 and Hollister say, "This species can be considered only as a very rare 

 summer visitor from the south." They mention half a dozen speci- 

 mens taken in Wisconsin, three of which were shot by L. Ktimlien on 

 Lake Koshkonong in June, 1893. (Birds of Wisconsin, 1903, p. 13.) 



Genus HYDROCHELIDON Boie. 



29. Hydrochelidon nigra surinamensis (Gmel.). 



Black Terx. Marsh Tern. 



Distr.: Temperate and tropical America, from Alaska to the Fur 

 Countries south to South America; breeding from the middle United 

 States west of the Alleghanies, northward. 



Adult in spring: Head and under parts (except under tail coverts), 

 black; back, wings and tail, slaty gray; under tail coverts, white; 

 primaries, dusky slate color, palest on the inner webs, the shafts of 

 the feathers, brownish white; bill and feet, black. 



Adult in fall and winter: Forehead, back of the neck, and under 

 parts, white or whitish; back of the head, black, mixed with white; 

 wings and back, gray. 



