A comparison of foliage use and tree height selection by birds in unlogged and logged mixed-coniferous forest

Abstract

Tree height selection and use of the available foliage by birds were examined in two mixed-coniferous forests in the White Mountains, Arizona, USA, during 1973 and 1974. A comparison of avian habitat use between a natural forest and one which had recently undergone a moderately heavy overstory removal form of timber harvesting, revealed that in both areas tall and moderately tall trees were preferred. Comparisons were made for the composite avian community and, in particular, for the yellow-bellied sapsucker Sphyrapicus varius, mountain chickadee Parus gambeli, ruby-crowned kinglet Regulus calendula, yellow-rumped warbler Dendroica coronata, and dark-eyed (= grey-headed) junco Junco hyemalis caniceps. Taller trees provided substantially more foliage and substrate for nesting and foraging than did shorter ones. Foliage use by birds in the unharvested plot suggested that foliage was being used in approximately the proportion in which it was available. This was not true in the modified plot where quaking aspen Populus tremuloides—the only tree species not logged—comprised 53·1% of the total available foliage volume. The biggest discrepancy between bird use and foliage volume occurred between 9 and 21 m from the ground. Within this height interval aspen represented 63·8% of the total volume. The subsequently derived bird use curve reflected the reduced desirability of aspen for most avian species.