Bird of the Month - March 2003
 

Rufous-crowned Sparrow
Aimophila ruficeps

by David Fix

Many surprises were uncovered by birders during the five years of field work for the Humboldt County Breeding Bird Atlas.  Among the more dramatic and satisfying events for those involved was the discovery in May 1998 of a population of Rufous-crowned Sparrows (Aimophila ruficeps) in the county.  This is a species characteristic of sunny, dry slopes in the foothills of California and the Southwest.  Rufous-crowned Sparrows were previously known to occur as far north as north-central Mendocino County.  Subsequent field work has shown that these birds are uncommon and a bit localized, yet they can be encountered given patience and perseverance.  They appear to be found in our area throughout the year.

Rufous-crowned Sparrows are known to few persons other than birders, as their preferred habitat lies well beyond the bounds of cities and suburbs.  Slopes grown to scant grass, scattered dry-site shrubs, and a few oaks may furnish these sparrows with all they require.  Good habitat often features stony ground, a talus slope, riverbank bluffs and boulders, or rock outcrops.  All of the Rufous-crowned Sparrows yet detected in Humboldt County have been along, or on slopes shortly above, the main stem Eel River from the vicinity of Fort Seward upstream to the Trinity Co. line.  Observations from Island Mountain, a bit further upstream, suggest that a more or less continuous smattering of these sparrows could extend from Fort Seward up the Eel canyon into central Mendocino County.  The extent to which this population might spread out in side drainages or upslope toward the ridges is undetermined.

This is one of many species in the typically southwestern genus Aimophila, which also includes the Bachman’s Sparrow of piney woods in the s.e. United States.  With a few exceptions, these are drab and indistinctly-marked ground birds.  Rufous-crowned Sparrow may be recognized by its reddish-brown crown, plain pale-gray breast, thin black eye-line, and thin, complete white eye-ring.  A whitish ‘whisker’ stripe bordered by a thin black line can be seen on each side of the face. An aid to identification is the plaintive ‘dear, dear, dear’ heard from the base of a rockslide or patch of stony, shrub-dotted hillside.  The pleasing song may suggest that of a House Wren, Lincoln’s Sparrow, or Lazuli Bunting.

The first time Rufous-crowned Sparrow was found in Humboldt, the observers (Tom Leskiw and John Hunter) topped off the feat by locating a nest!  These sparrows nest on or very near the ground, laying 3-4 eggs.  Details of the species’ life history are not well known. 

This is one of only a few bird species common in California, yet reaching the northern limit of its range at the edge of the ‘redwood curtain’.  And YOU can look for--and enjoy--this interesting bird by participating in the joint RRAS-Native Plant Society outing scheduled for April 27^th.  Watch the front page of The Sandpiper for details.