20 GULLS AND TERNS 



and leg's black ; tarsus shorter than middle toe with claw ; bill yellow, 

 with greatest depth at base ; tail slightly emarginate, or forked. Adults : 

 back and wing-s light bluish gray, live outer primaries tipped with black ; 

 rest of plumage pure white. Young : like adults, but with black or slaty 

 on back of neck and across ear coverts. Length : 16.00-17.70, wing' 12.25, 

 bill 1.40-1.50. 



Distribution. — North Pacific and Bering' Sea; south in winter casually 

 to Lower California. 



Nest. — On inaccessible shelves of rock, made of grass and moss cemented 

 with mud. Eggs : usually 2, gray, spotted with brown. 



The kittiwakes reach Alaska before the ice breaks up, and hunt 

 for food in the tide cracks along shore. In the breeding season 

 they take to the cliffs of the mainland or the rocky islands. From 

 the end of August they hunt in the inner bays and mouths of small 

 streams, but as they are strictly tide-water birds rarely go up the 

 rivers. In October the ice forming on the bays drives them south. 



GENUS LARUS. 



General Characters. — Bill deeper through angle of lower mandible than 

 through nostril ; tail square across end ; hind toe small but perfect. 



KEY TO SPECIES. 



1. Size large, wing 15.00 or more. 

 2. Wing without any black. 



3. Quills white or pale gray shading to white at ends. 



glaucus, p. 21. 

 3'. Quills clear gray with white tips .... glaucescens, p. 21. 

 2'. Wing quills partly black at all times. 



3. Mantle dark slaty gray in adult Occident alis, p. 21. 



3'. Mantle light gray in adults. 



4. Lower mandible in adult with subterminal spot of red and spot of 



black californicus, p. 23. 



4'. Lower mandible in adult with subterminal spot of red only. 



5. Mantle delicate pearl gray argentatus, p. 22. 



5'. Mantle slightly darker gray vegEe, p. 23. 



1'. Size medium or small, wing under 15 (rarely over in delawarensis). 



2. Breast always dark slaty gray heermanni, p. 24. 



2'. Breast always white in adult, mottled in young. 

 3. Head never black ; white in adults. 



4. Bill yellowish, with black band near end in adults. 



dela-warensis, p. 23. 

 4'. Bill greenish, without black band. 



5. Third quill with subterminal white spot in adult. 



brachyrhynchus, p. 24. 

 5'. Third quill without subterminal white spot in adult. 



canus, p. 24. 

 3'. Head black in summer adults, size small. 



4. Bill and tips of outer quills black . . Philadelphia, p. 26. 

 4'. Bill dark red in adult, quills not tipped with black. 



5. Three outer quills mainly black .... atricilla, p. 25. 

 5'. Five outer quills with tips and base white . franklinii, p. 25. 



