STERNA TEUDEAUI, TEUDEAIj's TEEN. C75 



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

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

 form and prf>portion, and pattern of coloration, as well as in seasonal changes of X''"™- 

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

 gronp can be divided into sections. Specific characters likewise aje sometimes a little 

 obscnre, 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 occipital patch, and 

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

 ers have little of the elongated filamentous character they possess in summer. The 

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

 egated on the upper parts with brown markings. 



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

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

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

 by the following brief diagnoses : 



Analysis of 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. 



u.. 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 parts decidedly 



paler than upper Tiirundo. 



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 supei-ciliaris. 



Bill and feet black aleulica. 



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



Mantle blackish-brown ; crown the same fuliginosa. 



Mantle smoky gray ; crown much darker anostlusta. 



Note. — The above analysis is based upon adult summer birds, and is nob available for 

 the young in which the characters, especially of color of the bill and feet, may be materi- 

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

 detailed descriptions. S. porllandica is not presented here. 



STEEISTA TRUDEAUI, Aud. 



Trndeau's Tero. 



sterna trudeaui, Aud., Om. Biog. v, 1839, 125, pi. 409 ; Syn. 1839, 319 ; B. Am. vii, 1844, 

 105, pi. 435 (New Jersey and Long Island). — GiK., B. L. I. 1844, 354. — Lawr., 

 B. N. A. 1858, 861.— CouBS, Pr. Phila. Acad. 1862, 542.— Schl., Mus. P.-B. Sternm, 

 p. 29.— SCL. & Salv., p. Z. S. 1871, 570.— COHES, Key, 1872, 322. 



Thalasaeus trudeaui, Bp., Comptes Eendus, 185(5, 772. 



Phoetusa trudeaui, Blas., J. f. 0. 1866, 73. 



Sler*na frobeeni, Phil. & Landu., Wieg. Arch. 1863, 125 ; Cat. Av. Chil. 49. (Sol. & Salv.) 



DiAG. S. corpore perlaceo, capite et tectricihus alarum inferioribus albis, vittd transoculari 

 nigrd, rostra rubescente, nigro-dncto, apicc fiavicante. 



Hob. — South America. Brazil {Scl. & Sab:). Chili (Phil. & Landb. ; Leybold). Bue- 

 nos Ayres {Mus. S. I.}. Atlantic coast of United States {Auditbmi & Trudeau). 



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

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



