Heath Hen

With such a lack of information pertaining to the Heath Hens of the mainland and Martha's Vineyard, it seems that while popular ideology in separating them is based almost soley on their pinnae and axillaries (which according to Ridgway & Friedmann (1946), the axillaries are almost wholly white, not the heavily barred like is so often mentioned), a much more logical perspective would be from the tone of their plumage, broad barring and their tails. Being a bird that inhabitated woodlands areas more so than the wide open plains that the Greater Prairie Chicken frequents, the colors of the birds seem to be reflecting what best suits them in their native habitats.

Pinnae even in the Greater Prairie Chicken vary in width, length, and can be squared at the ends to somewhat narrowly rounded. So it is easily feasible that this was the same for the Heath Hen. From museum specimens  viewed, it varies from a sharp needle-lke point, to a narrow roundness seen in the Greater Prairie Chicken. That is one of the reasons many of the pictures show features that seem to show the most consistencies.

 A cropped picture of the Heath Hen found at the New York State Museum showing pointed pinnae

Now a crop from the Heath Hen found in the Boston Museum of Science, showing pointed pinnae.

Here an enlarged crop of a Heath Hen found at the University of Michigan showing rounded pinnae.

 Another museum Heath Hen that like the previous three show all the typical characteristics known to the Heath Hen, just showing variances in a feature that is used as its "defining characteristic".

 Enlarged pinnae of a Heath Hen skin specimen found in the Virginia Tech Museum of Natural History. He also shows rounded pinnae:

With upland birds, subspecies are often the result of geographical separation. With them being found in different habitats, there are almost always morphological differences that are distinct for that given subspecies. Some more than others of course, but identification can be tuned in once those areas of consistent differences are found.