1919-] Hieraaetus ayresi. 175 



buff, almost brownish rufous on the upper breast and fading 

 into buff on the thighs and abdomen, broadly streaked with 

 dark brown on the breast, and more narrowly on the flanks 

 and upper abdomen; all these streaks are spear-shaped, and 

 on the sides of the upper breast only the edges of the feathers 

 are rufous. 



How H. ayresi originally became confused with H. spilo- 

 gaster I am not sure, but I think perhaps the late Dr. P. L. 

 Sclater may have been responsible, as 1 have found the follow- 

 ing in the volume of ' The Ibis ' for 1864, where Dr. Sclater, 

 in describing a collection of birds made by Dickinson on the 

 Zambezi, makes the following remarks under the head of 

 S. spilogaster (p. 304): — " This very interesting series shows 

 that Mr. Gurney's S. mjresi is the immature form of 

 S. spilogaster. Wolf's plate in the ' Ibis ' represents the 

 immature plumage in nearly every respect, except that 

 Dr. Dickinson's specimens show still less signs of a crest 

 than are depicted in the plate of -S^. ayresi, and the still 

 younger bird has the under surface uniform brown, with 

 scarcely a single indication of spots. In the youngest speci- 

 mens .... the under surface becomes white densely spotted 

 with black spots, the tail being also strongly barred across. 

 In the perfectly adult the spots wear off, and the bird becomes 

 white beneath, with spots only on the breast and flanks. In 

 this plumage the tail has a broad subterminal black bar." 



From the above it seems clear to me that Dr. Sclater had 

 before him both adult and young specimens of H. ayresi 

 and spilogaster. Again, Gurney in his excellent Notes on 

 Sharpens ' Catalogue of Accipitres in the British Museum,' 

 writes as follows (Ibis, 1877, p. 421):— "There is, however, 

 a variation in the markings of the under surface in specimens 

 of N. sjnlogaster, to which I am desirous of briefly alluding. 

 Two distinct phases of such markings occur in adult speci- 

 mens, or at least in specimens which are so far adult as to 

 have passed beyond the stage of plumage which characterizes 



this Eagle in its first year Thus in some individuals 



the white of the underparts is merely interspersed with sparse 

 and narrow dark shaft-marks whilst in other specimens 



