CAVITY-ENTRANCE ORIENTATION AND NEST-SITE USE BY SECONDARY HOLE-NESTING BIRDS

If cavity-entrance orientation confers some benefit (e.g., thermoregul ation of eggs and young) to secondary hole-nesting birds, individuals should use cavities with certain entrance orientations, and the orient ation of a cavity's entrance should influence reproductive success. Du ring a 2-yr study conducted at natural cavity populations in southeast ern Ontario, Tree Swallows (Tachycineta bicolor) were found to prefer cavities whose entrances faced S-SE, but the orientations of cavity en trances did not differ between pairs that fledged young and those whos e breeding attempts failed. European Starlings (Sturnus vulgaris) did not show a preference for cavities whose entrance faced a specific com pass direction. The conclusions of other similar studies are reviewed and several reasons why research concerned with the influence of cavit y-entrance orientation on nest-site use by secondary hole-nesting bird s has yielded inconsistent conclusions are discussed.