posted November 12th, 2009; last edited April 9th, 2010 –– David Sibley

Variation in Ruffed Grouse tail patterns

Since The Sibley Guide to Birds was published in 2000 I’ve received several comments and questions about the fact that I illustrated the displaying male Ruffed Grouse with a broken tail band (not a solid dark band continuing across the two central tail feathers). Readers note that males are supposed to have complete dark tail bands, while females have broken bands.

I based my illustration partly on the text from The Ruffed Grouse – Life history, Propagation, Management, by Gardiner Bump et al., published in 1947 by the State of New York Conservation Department. On page 39, discussing differences between the sexes, they say:

Perhaps the most diagnostic external feature is the tail. Birds having the broad, dark, subterminal band uniform over all tail feathers are almost invariably cocks, only one exception having come to the authors’ attention. But, if this band is broken on the two middle tail feathers, the bird may be either male or female.

They go on to describe other subtle and inconclusive differences between the sexes that may be used in combination by experienced observers to judge the sex of an individual grouse, such as the larger black neck ruff and the more distinctly pale-spotted upper tail coverts of males. So, while the tail band is the most conspicuous and useful difference between the sexes, it is not entirely reliable. I actually made a choice to illustrate a male with a broken tail band, rather than a typical male (I must have been feeling a bit contrary that day). Perhaps I should have chosen to illustrate a more typical displaying male with a complete tail band, but my illustration does seem to have called attention to a common misconception about grouse plumages.

One further comment is that some of the published photographs of displaying birds with broken tail bands probably are females. For example the photo in the Audubon Society Master guide to Birding (Volume 1, page 283). Females don’t drum, but they do strut occasionally (Bump et al.). I have seen this behavior once, in Washington state, when a female with small chicks strutted around agitatedly on a dirt road – just as the bird in that photograph seems to be doing. Compare the relatively small black neck ruff of that bird with photos of displaying males such as in Kenn Kaufmann’s guide, as well as in Bump, et al. page 66.

In summary, a Ruffed Grouse with a solid tail band is almost certainly a male; one with a broken tail band is probably a female but could also be a male. The strutting display behavior can be performed by both sexes, but only females tend the young.

This is an edited version of a comment first posted on the ID-Frontiers listerv in Aug 2001 (link).

Leave a Reply

  

  

  

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>