ROOSTS USED BY MATERNITY COLONIES OF SILVER-HAIRED BATS IN NORTHEASTERN OREGON

Ten silver-haired bats (Lasionycteris noctivagans) that were pregnant or lactating were radiotracked to cavities in 17 trees. Twenty availab le trees containing cavities were randomly selected for comparison. I measured 19 characteristics of cavities, trees, and habitat in 0.1-ha plots centered on each tree. Increased insolation and retention of hea t, which would particularly benefit maternity colonies, may have been achieved by roosts being high in trees and roost trees being farther f rom other tall trees and in earlier stages of decay. Protection of non volant young from terrestrial predators and newly volant young and adu lt females from aerial predators may have been provided by roosts loca ted high in trees that retained hard wood and that were distant from t rees that could restrict flight to and from the roost. Roost trees wer e taller, retained more of their tops, and more often protruded above the canopy than available trees, making them conspicuous in the audito ry and visual landscape.