12. OCEANODROMA MARKHAMI (Salvin). 



(MARKHAM'S FORK-TAILED PETREL.) 



(Plate 7.) 



Cymochorea markhami, Salvin, P. Z. S., 1883, p. 432 ; Tacz., Orn. Perou, III., p. 462 



(1886). 

 Oceanodroma markhami, Ridgway, Man. N. Amer. Birds, p. 71 (1887) ; Salvin, Cat. 



Birds Brit. Mus., XXV., p. 354 (1896). 



O. tristrami similis, vix minor, sed tarso et digitis gracilioribus, debilioribus 

 distinguenda. 



This species is founded upon two female birds procured by Admiral A. H. 

 Markbam, off the coast of Peru, one in Lat. 10° 40' S., Long. 75° W., the other in Lat. 

 23° S., Long. 73° W. Both of these specimens have passed from our collection into 

 that of the British Museum. 



The late Osbert Salvin, who described the species, considered that it was 

 separable from 0. tristrami by reason of the shorter tarsus (1 in.), middle toe and claw 

 (1.15 in.), and the distinctly plumbeous head and mantle. In 0. tristrami the head 

 and mantle are darker, and the tarsus and toes are decidedly longer and more 

 robust. The plumbeous or slaty shade which is seen in many of the Fork-tailed 

 Petrels seems to me merely indicative of freshly moulted, or breeding, plumage ; it 

 disappears as the feathers become worn, and is by no means a character for the 

 separation of one species of Oceanodroma from another. 



Both 0. tristrami and 0. markhami have much more slender bills than 0. melania, 

 the culmen of the first two measuring 0.7 inch, while that of 0. melania is only 0.6 inch, 

 and the bill is shorter and stouter. In plumage these three species resemble each 

 other. 



The two specimens of 0. tristrami examined by me (vide antea, p. 20) gave the 

 following measurements: — Wing, 6.8-7.2 inches; tarsus, 1.1-1.15; middle toe 

 and claw, 1.1-1.15. 



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