2p8 SNODGRASS AND HELLER 



This plumage is characteristic of adult males of all species of the 

 subgenera Geospiza and Cactornis and represents the farthest advance 

 toward complete melanism that any of the Geospizce have reached. 



There are all gradations between Stages V and VI. The black 

 color invades the lower breast, sides and abdomen as the pale margins 

 of the feathers disappear, the latter color remaining longest on the 

 lower abdomen, flanks and under tail coverts, never entirely disap- 

 pearing from the tips of the latter, and most of the blackest birds have 

 the under tail coverts broadly margined with pale rusty or buffy. 

 Also the primaries never become pure black, but in all cases retain a 

 distinct brownish color. 



Plumage of Nestlings. Very young birds having yet no wing 

 quills have four groups of very fine plume-like feathers on the head, 

 two on each side. One group forms an oblique line on the dorso- 

 lateral aspect of the head extending from a point above, and a little 

 back of the middle of the eye, backward and downward, ending a 

 little below the upper level of the orbit and over the posterior end of 

 the ear slit. The second group is situated on an oblique line on the 

 lower part of the back of the head on a level with the ear ; it is shorter 

 than the upper, and extends from without downward and inward. On 

 the body and appendages there are eight groups of these plume feathers, 

 arranged in four pairs as follows : a longitudinal row on the posterior 

 edge of the forearm, a transverse line across the back of the middle of 

 the humerus, a transverse line across the back of the femur near its 

 proximal end, a row along each side of the median line of the back on 

 the position of the enlarged part of the dorsal pteryla of later stages. 

 There is no plumage on the ventral surface of the head or body at 

 this age. 



The young wing quills, in nestlings a little older than those de- 

 scribed in the last paragraph, are of a pure bluish-slate color, tipped 

 with pale .buffy- white. The greater coverts of the primaries are the 

 same as the quills. The middle and lesser primary coverts and all the 

 secondary coverts have long reddish-brown terminal parts. The tips 

 of all the coverts, especially those of the secondaries, bear long and 

 very fine buffy plumes. In older specimens not only the wing coverts 

 but also the feathers of the middle of the back are strongly tipped 

 with reddish-brown. 



Pterylosis. The following description of the pterylosis of Geo 

 spiza fulginosa applies to all members of the genus. The dor- 

 sal pteryla runs down the back of the neck as a very narrow band, 

 being much narrower than the cervical part of the ventral pteryla. At 



