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 206 VoL. X HUACHUCA NOTES By F. C. WILLARD URING a number of seasons spent collecting in the Huachuca Mountains, in Cochise County, Arizona, I have noticed a great difference in the altitude at which vario.us species were to be found nesting on the eastern and the western slopes. A description of the range may be desirable to understand the difference re- ferred to. The main ridge extends from south-east to north-west. On the east a flat mesa extends froin the San Pedro river to the foot of the mountains, which rise rather abruptly but uniformly from this point to the summit of the main ridge some 5000 feet higher up. .The mean altitude of this ridge is 9000 feet. The average distance is about seven miles by trail. Several lateral ridges extend toward the east nearly to the mouths of the canyons and at a hight little less than that of the main ridge. These laterals are the partition walls between a number of deep and cliff-lined canyons. ' Going over the divide onto the western slope the whole character the mountains changes. The descent is very abrupt for the first two miles, after which it is gradual, ending in a number of low hills and rolling mesas, barren on the ridges, with a scattering growth of oaks on the slopes. There are no lateral ridges of any hight on this side and the canyons are more shallow and more poorly watered, with a growth of trees scanty in comparison with that o/the eastern slope. The growth for the first two miles down from the ridge is practically all scrub oak brush so thick that it is impossible to walk thru without cutting atrail. This zone is very limited in bird life. Black-throated Gray Warblers nest here at 8000 feet, while on the east they are mt in any numbers over 7000 feet. Roadrunners nest in these thickets and are practically unknown on the east above the foothills, alti- tude 5000 feet. Arizona Juncos and Mountain Towhees complete the list of birds nesting here but they are found also at the same altitude on the eastern slope and on the summit. On top of the main ridge and on the high laterals on the east, Chestnut-backed Bluebirds, Western Robins and Rocky Mountain Nuthatches nest. They are absent from the eastern side but are even more common at 4000 feet on the west- ern slope than on the summit. The Violet-green Swallow nests on the summit and down to 7000 feet on the east. It does not nest at all on the west. The Lucy Warbler nests commonly up to 4500.feet on the west, but I have no record of its nesting within eight miles of the foothills on the San Pedro side. Plumbcons Vireos nest at 4000 feet on the west and not under 6000 feet on the east. The Stephens Vireo is present in a few localities at about 6500 feet on the east and is entirely absent from the west. The Brewer Sparrow nests at 4000 feet on the west and is entirely absent on the east. Long-crested Jays nest commonly at 6000 feet on the east but only a few pairs on the v/est, and those right close to the ridge, not lower than 7000 feet. Desert Sparrow Hawks are quite common on the west nesting in hollows in the sycamores along the canyon bottoms. They also nest on the summits of the ridges, but none at all in the canyons on the eastern side. Western Nighthawks nest on the flat mesas between the canyons on the western slope but are rarely seen within several miles of the mountains on the San Pedro side.