Friday, March 5, 2010

Hairy and Downy Woodpeckers

Most birders do not have too much trouble identifying Downy and Hairy woodpeckers. 
The Downy Woodpecker is smaller than the Hairy and the Downy's bill is definitely shorter than the head is wide.  On the other hand, the larger Hairy Woodpecker's bill is usually at least as long as the head is wide. 
It surprises me, then, when I have trouble telling the relative size of the two species, specially here in Minnesota. Sometimes I have to check the  tail feathers of the woodpecker in question.  Downy Woodpeckers almost always have two spots or bars on their outer tail feathers. 
Compare the Downy Woodpecker tail above with the enlarged photo of a Hairy Woodpecker below.  The black tail bars are absent on the Hairy Woodpecker.  (I have only very rarely banded Downy Woodpecker with white outer tail feathers--so this field mark is not fool proof.)

As far as size goes, I wondered if my difficulty with relative size was due to actual differences or just to my aging eyes.  I may be correct in thinking Hairy Woodpeckers are smaller in Minnesota.  Two of the 17 races of Hairy Woodpeckers are found in North Dakota, South Dakota, and Minnesota. The Northern Hairy Woodpecker, Picoides villosus septentrionalis, is found north of us (and in northeastern South Dakota and perhaps in extreme northern Minnesota). The northern bird is larger and whiter than the Eastern Hairy Woodpecker Picoides villosus villosus, the race expected in Northfield (and in most of Minnesota).  In these photos, the bottom two Hairy Woodpecker photos were taken in Aberdeen, South Dakota.  Note how white this bird is compared to the Minnesota photo at the beginning of this blog entry! The Northern Hairy Woodpecker does range further south in the winter, and perhaps, as indicated by these photos, could be identified in the field.

My sources for this information are Roberts, The Birds of Minnesota, UM Press 1936 and also Jackson, Jerome A., Henri R. Ouellet and Bette J. Jackson. 2002. Hairy Woodpecker (Picoides villosus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/702

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