Feb. 25. Juniper Flat, 5600 ft., Chisos Mts., Brewster Co., Texas. The only time I tried this (by hissing) in an area largely oak about 5500 ft. elev. Also attracted were a Hutton Vireo and a Bewick Wren. (Both these species were heard singing earlier on the Flat proper). The vegetation on the Flat was juniper predom-inately (the weeping juniper was not there, however). Oaks and pinyons were there although less abundantly. In some cases the growth was fairly dense, the height of the trees being 15-20 ft. or an average. The aspect reminded me of the oak belt in Southern Arizona except that Yellow Pine was absent. Avian associates which furthered the impression were Aphelocoma ultramarina and A. coerulescens, Vireo huttoni, Thryomanes Balyanophyga formicivora and Pipilo maculatus. During the 1 1/2 hours or so that I actually watched the titmice, I would say that they spent 95% of their foraging time working on juniper bark. While they would forage in oaks, they did not seem to tarry long in them but moved along into junipers. Thus as far as the "Mexican" avifauna is concerned, the Black-crested Titmouse appears more to be the analogue of the Plain Titmouse at the northern margin of that floral-faunal complex. During the morning I heard no song which I could definitely attribute to this species. Some of the birds seemed to be paired and acted so even when associated with additional titmice. In one case (incident at 10:55) two pairs seemed to be spacing them-selves and establishing boundaries. Earlier, one "pair"