MONOGRAPH OF THE PETRELS. 



mantle, neck, and crown of head paler brown ; entire sides of face, cheeks and 

 throat, white ; longer scapulars and wing-coverts darker than the back, and 

 inclining to blackish ; quills black, the outer primaries with pale yellow shafts ; 

 secondaries also blackish, the greater part of the inner web white towards the base : 

 inner secondaries greyish-brown on the inner web ; lower back, rump, and upper 

 tail-coverts brown ; tail-feathers blackish-brown, white at the extreme base, where 

 the shafts are yellow ; under-surface of body lighter brown than the back, the 

 feathers of the lower throat and chest with paler brown margins ; the breast and 

 abdomen paler and more ashy-brown than the chest, with white bases to the 

 feathers ; under tail-coverts very dark brown, like the flanks ; axillaries white, 

 most of them with brown at the ends ; under wing-coverts white, with a broken 

 band of black round the edge of the wing ; quills blackish below, white or greyish 

 towards the base of the inner web of the secondaries ; " bill whitish horn-colour ; 

 feet fleshy- white ; iris brownish black." Total length, about 40 inches ; culmen, 

 5.8 ; wing, 25.0 ; tail, 7.5 ; tarsus, 4.35 ; middle toe and claw, 6.3. 



That all young birds follow the same sequence in their change towards the 

 adult stages of plumage I should not like to affirm, but the process follows the same 

 general lines. Sometimes the sides of the face are pure white, like the throat, 

 at other times they are brown, but in the latter case the ear-coverts are more or less 

 mottled with white, indicating a progress towards the next stage, when the ear- 

 coverts are white. As the young birds proceed towards maturity, if one may 

 judge from a specimen in the British Museum, procured in the Cape Seas by 

 Mr. E. M. Langworthy, the second plumage is similar to that described above, but 

 has more distinct sandy-brown margins to the feathers of the upper-surface, 

 especially on the neck ; evidences of the forthcoming adult plumage are also to be 

 seen in the presence of some pure white plumes, having the characteristic zigzag 

 vermiculation of the fully adult bird on the back and fore-neck. This specimen 

 has the forehead and sides of the crown, and sides of the face, white, but the ear- 

 coverts are brown like the head. The under-surface is brown, as in the young 

 specimen described, but on the abdomen are traces of zigzag bars, showing that a 

 barred stage of plumage is foreshadowed even in the brown stage. 



Some of the brown birds are distinctly paler on the breast and abdomen, 

 others are apparently passing from a dark to a sandy brown under-surface. In 

 Mr. Rothschild's Collection are two specimens, which, though to all appearance 

 immature, have a perfectly white breast and abdomen. In some birds which are 

 apparently adult, and have even been procured off the nest, there are indications 

 of immaturity, in the brown blotches on the back, and the dark patch on the 

 crown. The zigzag transverse bars are coarse, and unlike the slender vermicula- 

 tions indicating a very old bird, in which the head is pure white. 



Having traced the immature brown-coloured bird to the white fully adult 



316 



