BIRDS OF NORTH AND MIDDLE AMERICA. 675 



Bill stout, the exposed culmen shorter than middle toe without 

 claw, its depth at base equal to or slightly greater than its width at 

 same point and at least equal to one-third the length of exposed 

 culmen; supra-nasal saddle, measured from loral antia, longer than 

 distance from its anterior end to tip of the strongly dccurved or unci- 

 nate tip of maxilla; gonys less than half as long as mandibular rami 

 (measured to point of malar antia), rather strongly ascending term- 

 inally, faintly concave, its basal angle prominent; nostril with anterior 

 end nearer to tip of maxilla than to loral antia, the latter on nearly 

 the same vertical line as malar antia or slightly anterior to it, the 

 mental antia decidedly anterior to both. Wing moderately long, the 

 longest primary (outermost) exceeding distal secondaries by not more 

 (sometimes less) than half of the length of wing; primaries 

 broad, rounded at tips, their shafts thick and rigid; sec- 

 ondaries relatively short and broad, with inner webs longer 

 than outer webs; tertials elongated, but falling considerably short of 

 tips of longest primaries. Tail less than half as long as wing, nearly 

 truncate, the rectrices sub-truncate at tips, the middle pair project- 

 ing slightly, if at all, beyond the next pair; tail-coverts very long 

 and full, the lower ones reaching to or beyond tips of lateral rectrices. 

 Tarsus as long as middle toe without claw, strong, the lower haK or 

 more of the acrotarsium covered with a single series of obliquely 

 transverse scutella, the upper portion with a double row of similar 

 but shorter scutella, the planta tarsi covered with small, irregular 

 scales, the sides of tarsus with larger hexagonal scales; outer toe 

 slightly shorter than middle toe, the inner toe much shorter, the 

 hallux very short; anterior toes fully webbed; claws relatively large, 

 strongly curved, acute, that of middle toe with inner edge dilated. 



Coloration. — General color brown or sooty, usually indistinctly 

 streaked with light rusty, cinnamon, or buff}", especially on neck and 

 back; primaries whitish basally. 



Range. — Northern portions of North Atlantic and southern parts 

 of South Atlantic oceans, southern parts of Indian Ocean, Antarctic 

 Ocean, seas near New Zealand, and Pacific coast of Chile and Peru. 

 (At least four species or subspecies.) 



KEY TO THE SPECIES OF MEGALESTRIS.O 



c. Bill relatively longer and narrower, with anterior edge of eupra-nasal saddle (\-iewed 

 from above) strongly concave; under parts more or less rufescent, and back 

 streaked or mottled with rufous or cinnamomeous. 



<i Mr. Gregory Mathews (Birds of Australia, ii, 1913, 496) recognizes eight forms of 

 this genus, referred to three species, as follows: 



1. Megalestris skua skua. (Catharacta skua skua Mathews, Birds Australia, ii, 



pt. 5, Jan. 31, 1913, 496.— North Atlantic Ocean; Hudson Strait.) 



2. Megalestris skua antarctica. (Catharacta skua antarctica Mathews, Birds Aus- 



tralia, ii, pt. 5, Jan. 31, 1913, 496. — Falkland Islands, breeding; Gough 

 Island.) 



