From Edward Blyth [after 24 February 1867]1
years ago, and 〈 line excised〉 remarks were quite forgotten by myself.2 I have not much now to comment upon them. I remember that Gould assured me about the difference of sexes in the common Gallinule, saying that the female is both larger and handsomer—colouring; but a much more decided instance3 [missing section of unknown length]
The fact stated by Gould of the extraordinary development of the trachea in the female only of Rhynchea australis, is the more remarkable that nothing of the kind occurs in the female of R. bengalensis; yet the birds are scarcely distinguishable externally, except that the Australian species has shorter toes.4 [missing section of unknown length]
though more slowly in the females, the only difference being that the fully mature females are duller-coloured on the back.
In a remarkable hornbill (Aceros nipalensis) inhabiting the S.E. Himalaya and the mountains of Burma, the female (or what from analogy I presume to be such) has wholly black plumage with white tail-tip, whereas the (presumed) male has the head, neck, and lower-parts bright ferruginous.5 Now in a nestling bird of this species in the Calcutta museum, the colouring is that of the (presumed) male, and possibly the sexes may be thus distinguished from the first. They are slightly so in the British blackbird and stonechat;6 and in a parrakeet very common in Burma (Palæornis javanicus), the young from the first are conspicuously distinguishable by the male having the upper mandible coral-red, while in the female it is black; this continues for the first year at least, after the adult plumage has been attained, but finally the upper mandible of the female becomes red as in the male, and I have witnessed the change in a caged bird, besides that I have seen many specimens with the bill in process of change.7
By Ardeola I meant Ardetta, which is the name now given to the little bittern of this country and its immediate congeners.8 In Ardeola, of which the European squacco heron (A. ralloides ) is characteristic, there is very great difference in the summer and winter plumage, the latter being so similar in some of the races that they cannot be told apart, whilst in summer dress they are strongly distinguished.9
The seasonal change in the plovers and sandpipers is completed in India before the several species leave the country for their breeding haunts. We really know very little of the southern
Sexual differences in bird species and seasonal variation in plumage.
Please cite as
Darwin Correspondence Project, “Letter no. 6403,” accessed on 1 September 2016, http://www.darwinproject.ac.uk/DCP-LETT-6403