Notes on the use of the Creosote Bush by Birds
Notes on the Use of the Creosote Bush by Birds.-It is generally known that the extensive, pure stands of the creosote bush (Larrea divaricata) in the southwestern deserts seldom attract many birds. In the Tucson region of Arizona, we have walked through a mile of this inhospitable-looking shrub without seeing a single bird. However, when it occurs intermixed in or at the fringes of cacti,. mesquite, and catclaw associations we have observed that a considerable number of birds make use of it.
Verdins (Auriparus flapiceps) and gnatcatchers (Polioptila sp.) forage in the bushes throughout the year, evidently finding some insect food. Occasionally during the winter we have seen Audubon Warblers (Dendroica auduboni) and, in the spring, Pileolated Warblers (B’i’ilsonia pusilla) travelling from plant to plant searching the twigs. In April Cactus Wrens (Heleodytes brunneicapillus) begin to walk around the bushes peering upward into the branches for larger insects. When one is located it is caught by a quick jump. Then the wren usually climbs through the entire bush in search for more. This method is repeated at the next bush. Buds are nibbled by English Sparrows (Passer dontesticur) and House Finches (Carpodacus mexicanus), and we have seen both of these species pull off and crush the fuzzy fruits with their bills to get at the seeds inside. Although the creosote bush fruits ripen in enormous numbers each year, and are easily accessible, we have never observed any of the desert birds feeding on them regularly. We have a record of the Green-backed Goldfinch (Spinus psaltria) sampling the fruit, also. Occasionally the abundant yellow flowers are visited by the Blackchinned Hummingbird ( ArchiCochus alerandri).
English Sparrows sometimes break off the smaller, flexible green twigs and use them for the exterior part of their nests. Evidently the slender upright branches, the lack of support-forming intertwining twigs, and the scarcity of suitable forking make this shrub undesirable for nest location. The only nest we have ever observed in a creosote bush was that of a Black-tailed Gnatcatcher (Polioptila melanztra), found on May 26, 1944, near Rillito Creek, 2% feet above the ground in a small, slanting fork of a branch.-Annxns H. ANDERSON and ANNE ANDERSON, Tucson, Arizona, May 3, 1946.
