Key to Subspecies.
A. Crown black. Aestiv.
B. Crown black, the feathers fringed with green. Hiem.
a.Chin yellow, malar stripe absent or, if present, tinged with yellow…………M. f. feldegg, p. 271.
b. Chin and moustachial stripe pure white and distinct…………M. f. melanogriseus, [p. 272.
In their non-breeding haunts these two races overlap very greatly and it is quite useless comparing series of intermediate birds obtained in these places in Winter and trying to draw any deductions from such comparison. Breeding birds show the differences between the two races sufficiently well to justify their retention. Young birds certainly cannot be differentiated and young birds are those which travel furthest and are found most often beyond their usual migration routes and winter haunts.