The Leconte Thrashers of the San Joaquin

Abstract

In February, 1932, the writer and his companion, Mr. Ward C. Russell, found themselves on a brief trip south along the west side of the southern (upper) San Joaquin Valley, in west-central California. In attempting to trace the local distribution of certain mammals and birds in that territory, enough new facts concerning the Leconte Thrasher (Toxostoma lecontei) came to our attention to appear to warrant this special contribution on that species. In coming south Mendota, Fresno County, we first encountered the Leconte Thrasher about seven miles due east of Coalinga, in the same county, near the highway leading toward Tulare and about where Polvadero Gap is marked on the Coalinga sheet, U. S. G. S. Here Mr. Russell obtained a breeding male and heard or saw at least three others, the morning of February 21; they were in a tract of large-sized atriplex, or kind of salt-bush, along an arroyo. This is about where Goldman (1908, p. 205) found the species in 1907. He met with it from near Huron west to the Arroyo Los and collected specimens, both adults and full-grown young, June 29 to July 1. Human activities in the oil region immediately around Coalinga, including the arroyo Los Gatos Creek, have doubtless resulted unfavorably to the birdlife native there; at any rate, we saw no promising thrasher ground close around Coalinga. Also our own rapid reconnoissance of the immediate vicinity of Huron, southwestern Fresno County, failed to show appropriate ground for Leconte Thrashers, although there was evidence that tracts of atriplex brush formerly existed there. But there remains much good-looking Leconte Thrasher country about midway between Coalinga and Huron, and our sample was probably a fairly extensive population of the species there. This neighborhood, then, marks the northernmost limit of the range of the species west of the Sierra Nevada (see map, fig. 21). In our zigzagging about over the Tulare Lake basin, now throughout, we found no trace of this species; nor, in proceeding farther south, did we see any favorable ground for it till we approached Lost Hills, Kern County. Here, our route again cut into the piedmont belt of atriplex, good-looking for the bird in question, which probably extends with some interruptions southeast Coalinga along the entire west side of the Tulare Lake basin. But we did not stop to test the supposition, proceeding on to McKittrick. Here, within two miles northeast of this oiltown, in western Kern County, somewhat off the highway leading towards Bakersfield, we made a three-night dry camp, February 22 to 24, inclusive; and we obtained there the materials upon which most of the succeeding account is based. This locality (two miles east and northeast of McKittrick) is at about 1000 feet altitude, on ground sloping gently down northeastwardly toward Buena Vista Slough, with low hills close by to the west and south. It is in the focus of the rain-shadow the coast ranges-excessively and of desert aspect. Despite recent rains, copious for this place, much dry-surfaced bare ground was in sight. The new green stuff was restricted to the low places along draws or washes, to shady sides of hills, to spots which had been worked by burrowing rodents, and to patches beneath and close about bushes. Even though it was yet February, with unusually heavy snow mantling the mountains to the east, south and west of us, the mid-day sunshine was powerfully warming.