Abstract:
The acorn woodpecker is among the most common primary cavity nesting bird of the Oregon white oak woodlands. In most of
their range, acorn woodpeckers are dependent on granaries for acorn storage, yet little is known about their selection of granary
sites. We compared habitat characteristics within 12 m of granary and non-granary trees at 20 acorn woodpecker colonies in
Benton County, Oregon during the winter of 2001. Compared to non-granaries, granary plots consistently had greater oak basal
area and shorter shrub height, and granary trees were of larger diameter. Within each of the 20 sites, oak basal area was greater
near granary than non-granary trees. This, together with the selection for larger diameter granaries, suggests acorn woodpeckers
are more likely to locate granaries in the immediate area of high acorn production. Increased acorn production in the vicinity of
granaries is likely beneficial to the birds because minimal effort is expended in caching maximum forage. Our results shed light
on granary selection at the spatial scale of the immediate area surrounding granaries and suggest factors associated with acorn
woodpecker distribution at the landscape scale.
