Gila Woodpecker Nesting in Northern Baja California

Gila Woodpecker Nesting in Northern Baja California

NOTES GILA WOODPECKER NESTING IN NORTHERN BAJA CALIFORNIA JAMES W. CORNETT, Natural ScienceDepartment, Palm SpringsDesert Museum, P.O. Box 2288, Palm Springs,California 92263 The range of the Gila Woodpecker(Melanerpes uropygialis) coincides closely with the distributionof the Saguaro (Camegiea gigantea) and Cardon (Pachycereus pringlei)cacti of the Sonoran Desert (Robbinset al. 1983). The woodpeckers'nest cavitiesare usuallyexcavated in the trunksand branchesof thesegiant succulents and to a lesserextent in cottonwoods(Populus), mesquite (Prosopis), and willow ($alix) (Bent 1939). The range of the Cardon extends to within 130 km of the U.S. border (Wiggins1980) and presumablyGila Woodpeckersnest in this region.There is one record of a Gila Woodpeckerfrom "Las PalmasCanyon" in extreme northernBaja, beyondthe range of the Cardon (Grinnell 1928). Unfortunately,the preciselocation of "LasPalmas Canyon" is unknownand couldbe any of severalcanyons draining the easternslopes of the Sierra Juarez that harbor palms. On 15 May 1984 Jim Toenjesand I observedtwo pairsof Gila Woodpeckers44 km southof the U.S. border, in Tajo Canyon (32 ø 15 • 41 •' N, 115 ø 51 • 25 •' W), Baja CaliforniaNorte. Both pairswere callingvigorously. No Cardon cactiwere in the can- yon or on the surroundinghillsides. The only likely nestingsites were in dead standing Desert Fan Palms (Washingtoniafili•fera) and Blue Fan Palms (Erythea armata), of which there were 14 and 6, respectively,in the eastern5 km of the canyon. We did not, however,observe any activenests. Nearly 400 livingpalms with trunksexceeding 2 m in heightexisted in this portion of the canyon. The followingday I visitedBlue Palm Canyon (32 ø 22 • 31 • N, 115 ø 50 • 19 • W), also in Baja CaliforniaNorte, approximately24 km south of the U.S. border. Again, no Cardon cactiwere in the vicinity,and the only largetrees were Desertand Blue Fan Palms. I observeda single pair of Gila Woodpeckers,both of which were actively feedingyoung in a nestcavity in a dead Blue Fan Palm. The oasisin thiscanyon had 129 large palms, three of which were dead but still erect. Approximately122 DesertFan Palm oasesexist in the U.S. yet Gila Woodpeckers are not known to nest in any of these oases.One significantdifference between the palm oasesof northernBaja and southernCalifornia is the absenceof Blue Fan Palms in the U.S. groves,a palm speciesthat reachesits northern limit in Blue Palm Canyon. My studiesof palm oasessuggest that E. armata may require some precipitationin summer, which decreasesinversely with latitude in this region. Perhaps a lack of suitablenesting sites, i.e., Blue Fan Palms, in conjunctionwith insufficientsummer rain and resultantdecrease in food resourcesprevents the Gila Woodpecker from establishingitself at palm oasesin the U.S. I note alsothat EuropeanStarlings ($turnus vulgaris)frequently nest in many U.S. palm oases,most of which are locatedwithin 50 km of urban areas. I have yet to see a starlingin any of the palm oasesof Baja California Norte, all but one of which are located more than 75 km from the nearest town or city. LITERATURE CITED BenL A.C. 1939. Life historiesof North American woodpeckers.U.S. Natl. Mus. Bull. 174. Grinnell.J. 1928. A distributionalsummation of the ornithologyof Lower California. Univ. Calif. Publ. Zool. 32:1-300. Western Birds 17:139-140, 1986 139 NOTES Robbins, C.S., Brunn, B., and Zim, H.S. 1983. Birds of North America. Western Publ. go., Racine, WI. Wiggins, I.L. 1980. Flora of Baja California. Stanford Univ. Press, Stanford, CA. Accepted 20 February 1987 140 .

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