A REVISION OF THE FORMS OF THE LADDER-BACKED 

 WOODPECKER (DRYOBATES SCALARIS [WAGLER]). 



By Harry C. Oberholser, 



Assistant Ornithologist, Department of Agriculture. 



This paper is the outgrowth of an attempt to determine the proper 

 name for tiie ladder-backed woodpecker of Texas. The investiga- 

 tion has developed some interesting results, which it seems well 

 to publish collectively. The writer is under great obligation to 

 IVIr. Ridgway for the use of aU the material of this group that he 

 had brought together for his "Birds of North and Middle America," as 

 well as a large number of his measurements. Altogether 560 speci- 

 mens have been available, comprising the collections of the U. S, 

 National Museum, with that of the Biological Survey; the ifmerican 

 Museum of Natural History; the Academy of Natural Sciences of 

 Philadelphia; the Museum of Comparative Zoology at Cambridge, 

 including the Bangs collection; the Carnegie Museum at Pittsburg; 

 and the Field Museum of Chicago. 



The ladder-backed woodpeckers, Dryohates scalaris (Wagler), range 

 from the southwestern United States, in southern Colorado and 

 southern Utah, to southeastern Mexico and British Honduras, 

 chiefly in the Lower Austral and Tropical zones. They are strictly 

 resident, and are preeminently birds of the chaparral and cactus, 

 rarely frequenting the forest. In a general way the smallest forms 

 inhabit the south and the largest forms the north. The six cur- 

 rently recognized races are here increased to fifteen. The adult 

 females differ from the males in lacking all red on the pileum, black 

 taking its place, and in being of smaller size; otherwise the sexes are 

 identical. There is considerable individual variation in both size and 

 color. 



In all measurements, which are in millimeters, it has been the aim 

 to use, as far as possible, only typical specimens, so that the aver- 

 ages and extremes may represent, not the limits of intermediate 

 specimens, but standards for the various forms. 



The following key may be of some assistance for purposes of 

 identification, as well as serving for an exposition of salient characters. 



Proceedings U. S. National Museum, Vol. 41— No. 1847. 



139 



