28 



KEY TO PETRELS (Cont.) 



7 Two central-most upper tail coverts within the largely white rump 

 patch completely dark or partly dark OR only a few feathers on 

 either side of rump with at least some white; shafts of white rump 

 feathers dark; bases of outermost tail feathers usually dark, but 

 if white, then only for about 1 cm. 



LEACH'S STORM PETREL, light phase 



7' The several longest upper tail coverts in center of rump white 

 but with dark tips; shafts of white rump feathers white; lateral 

 tail feathers white at base for 2.5 cm or more. 



HARCOURT'S STORM PETREL 



8 Coloration blackish-gray all over (not brown), particularly on 

 ventral surfaces of wings; upper wing coverts not distinctly 



buffy (only slightly, if at all). 9 



8' Coloration brown, particularly under wing coverts; upper wing 



coverts very decidedly buffy forming a bar running diagonally from 

 the body to the wrist (not including scapulars); north of Pt. 

 Conception almost all with wings >144 mm (very rarely to 142 mm long). 



LEACH'S STORM PETREL, dark phase 



9 Wing length <130 mm; bill length <12 mm; central tail feathers longer 

 than or as long as outer ones (i.e., tail wedge-shaped or square, not 

 forked); upper tail coverts (rump feathers) extend about 2/3 the length 

 of tail feathers (Fig. 19b). LEAST STORM PETREL 



9' Wing 131-142 mm (very rarely to 145 mm); bill 13-15 mm; tail forked; 

 upper tail coverts extend only about 1/2 the length of tail feathers 

 (Fig. 19a). ASHY STORM PETREL 



10 Back, mantle of wings, and rump boldly checkered black and white; 



broad black band at tip of white tail. CAPE PETREL 



10' Coloration not as above. 11 



11 Underwings white with a broad black bar running from wrist to 

 "armpit"; breast white but belly charcoal gray; bill black, <29 mm 

 long and heavy in proportion (not slender; Plate 5); tarsus <38 mm. 



SCALED (MOTTLED) PETREL 



11' If underwings white then without the broad black bar referred to 

 above; if breast white then belly white also; bill brown, yellow, 

 horn color or pale, >29 mm but if 29-30 mm then especially slender; 

 tarsus >42 mm. 12 



