Arizona Race of Acorn Woodpecker Vagrant in California
Arizona Race of Acorn Woodpecker Vagrant in California.-Acorn Woodpeckers (Belanosphyra form&era) occur normally in California west of the crest of the Sierra Nevada and the desert divides where essential acorn-supplying oaks are present. There is but one published record of the occurrence of this species to the eastward in California, namely, at Carroll Creek at 5500 feet, near Lone Pine, Inyo County, September 8, 1911 (Grinnell and Miller, Pac. Coast Avif. No. 27, 1944:232). This station is near the Sierran forests where the woodpeckers are resident.
On October 19, 1945, near the summit of Eagle Mountain, at 4900 feet, in central Riverside County. California, far out in the desert, I came upon an Acorn Woodpecker in an open pifion. Among’the rocks of this desert mountain top is a sparse, dwarf woodland of pifions and scrub oak (see Miller. Condor. 48. 1946:75-79). Oaks were scattered about the area where the woodpecker was encountered, and upon’dissection of the bird acorn mast was found in the stomach.
The bird ($ no. 94189 Mus. Vert. Zool.) proves to be an example of the race of Arizona and Mexico, Belanosphyra formitivoru fornticivora (see Twentieth Suppl., A. 0. U. Check-list, Auk, 62, 1945:443), rather than B. f. bairdi of western California. The identification seems decisive by reason of the slight amount of yellow on the throat, the relatively narrow black chest band and the short wing (132.1 mm.) which the bird possesses. The area on Eagle Mountain is ecologically inadequate to support a resident group of Acorn Woodpeckers and no acorn stores were found. It may be assumed that this bird was a vagrant from one of the areas of residence in Arizona, the closest of which is in the Hualpai Range ninety miles distant across the Colorado River valley. In view of the sedentary habits of this species, this vagrancy is somewhat surprising. It is worthy of note that in crossing the desert this bird had found this small isolated area of scrub oak and had utilized its food resources. In this connection we may again draw attention to the remarkable deviation in instincts of the Central American race of this species (see van Rossem, Field Mus. Nat. Hist., Zool. Ser., 23, 1938:316-317) which has lost, or never acquired, the striking acorn feeding and storing behavior which so dominates the lives of most races of this group and which determines their habitat selection and distribution.- ALDEN H. MILLER, Museum of Vertebrate Zoology, Berkeley, California, April 5, 1947.