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Monday, March 12, 2012

Pygmy Nuthatch

Pygmy Nuthatch (Sitta pygmaea) — rare on Bodega Head, but more common inland.  This photo was taken in Sebastopol. 

They are the smallest of the three nuthatches in this area.  Note the gray-brown cap and dark eyeline, generally blue-gray feathers above and white (or buffy) below.  In the photo you can also see the relatively short bill and very long toes.

According to the Birds of North America, Aristotle used the Greek word “sitte” to refer to a bird that pecks at the bark of a tree — hence the genus, Sitta.  The nuthatch above is searching for food (insects, seeds) on a large redwood trunk.

Pygmy Nuthatches are gregarious and social.  You can often hear them before you see them, as they are quite vocal and their high-pitched twittering and piping calls are very distinctive.  They are found in flocks year-round.

Because of their small size (9–11 cm long), they are sensitive to cold temperatures.  To stay warm at night, they roost communally in tree cavities temperatures inside cavities with huddling nuthatches have been measured 9° above ambient. (Like chickadees, they can also undergo controlled hypothermia to save energy at night.)  Their need for tree cavities (especially dead snags) leads to a preference for old-growth, mature forests.

Like the Bushtit (see post on 3 February 2012), Pygmy Nuthatches are cooperative breeders, with breeding pairs assisted by 13 helpers.  Although they prefer pines throughout their range, a pair nested in an oak tree in our yard.  The opening to the cavity was incredibly narrow (see gray "doughnut" near bottom of photo below); the nuthatches entered it sideways!

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