STERNA TRUDEAUI. TRUDEAU's TERN. C75 



The genus Sterna, as restricted by most later ornithologists, includes the numerous 

 species which are closely allied to S. hiruiulo. They agree very closely in size, general 

 form and proportion, and patteru of coloration, as well as in seasonal changes of plum- 

 age. So closely is this resemblance maintained, that it is with some difficulty that the 

 group can be divided into sections. ^Specific characters likewise are sometimes a little 

 obscure, especially when we have to deal with immature specimens. 



In winter the species lose the bright color of the bill and tarsi, to a greater or less 

 degree, and also the black pileum, which is mostly restricted to an occijjital patch, and 

 a fascia on each side of the head. The long-forked tail is shortened ; the lateral feath- 

 ers have little of the elougated filamentous character they possess iu summer. The 

 young-of-the-year resemble the adults iu winter in most points, but are generally vari- 

 egated ou the upper parts with brown markings. 



Of the many species of the genus, nine or ten are kuowm to inhabit North America. 

 Of these, three {hirundo, macrura, and imradisea) are common to Europe and America, 

 while of those remaining, two have a wide trojiical dispersion. They may be recognized 

 by the following brief diagnoses : 



Analysis 9/ North American species of Sterna. 



A. Mantle pearl-gray. 



I. No black cap. 



Head whitish, with black bar through eye ; under parts like the 



mantle trudeaui. 



II. A black cap. 



a. No white frontal crescent. 



a'. Bill wholly or mostly red or reddish. 



Bill red, blackening at end. Feet coral-red. Outer 

 web of outer tail feather, white ; inner, gray or 

 dark. Tarsus 0.90, or more forsteri. 



Bill red, blackening at end. Feet coral-red. Outer 



web of outer tail feather, gray or dark ; inner, 



* white. Tarsus about 0.75. Under iiarts decidedly 



paler than upper Jiirundo. 



Bill wholly red. Feet vermilion. Tail feather as in 

 the last. Tarsus 0.65, or less. Under parts nearly 

 like upper macrura. 



v. Bill black, often red at the base. Feet reddish paradisea. 



h. A white frontal crescent. 



Bill yellow, tipped with black. Feet yellow superciliaris. 



Bill and feet black alcuiica. 



B. Mantle dusky. A white frontal crescent. Bill black. 



Mantle blackish-brown ; crown the same fnUginosa. 



Mantle smoky gray ; crown much darker anosthwta. 



Note. — The above analysis is based upon adult summer birds, and is not available for 

 the young in which the characters, especially of color of the bill and feet, nuiy be matfU'i- 

 ally different. These, especially of Sec. II, can only be determined by reference to the 

 detailed descriptions. S. portlandica is not presented here. 



STERI^A TRUDEAUI, And. 



Trutleau's Tern. 



Sterna trudeaui, AuD., Orn. Biog. v, 1839, 125, pi. 409 ; Syn. 1839, 319 ; B. Am. vii, 1844, 

 105, pi. 435 (N«w Jersev and Long Ihiand).— Giu., B. L. I. 1844, 354.— Lawr., 

 B. N. A. 1858, 861.— Cotncs, I'r. Phila. Acad. 186-2, 542. -Sen L., Mns. P.-B. Sterna;, 

 p. 29.— ScL. &, Salv., 1*. Z. S. 1871, .570.— CouES, Key, 1872, 322. 



ThahiHseuH trudiani, Br., Comptes Rcndus, 1856, 772. 



Phoctuna trudeaui, Bla.s., J. f. O. 18(56, 73. 



Sterna frobeeni, Pun,. & Landu., Wieg. Arch. 1863, 125 ; Cat. Av. Chil. 49. (Scl & Salv.) 



DiAG. S. corpore perlaceo, capite ct tectricibus alarum inj'erioribus albis, vittd (ransoculari 

 niyrd, rostra rubescente, nigro-cincto, apicc flavicante. 



//((/).— South America. Brazil (,S(7. & S«/c.). VhWi {riiil. <%: Landh. ; Leifbold). Bue- 

 nos Ayres {Mun. 6. I.). Athmtic coast of United Slates {Audubon & Trudeau). 



Adult, perfect plumage. — The bill ia noticeably stout for its length, especially deep at 

 the base. The culmen is regularly curved ; the outliue of the rami is a little concave, 



