Red Squirrel Nests in Witches' Brooms in Douglas-Fir Trees

Abstract

We examined a random sample of 105 felled Douglas-fir trees (Pseudotsuga men- ziesii) for nests. Some trees were infected by Douglas-fir dwarf mistletoe (Arceuthobium douglasii) and some were not. Nineteen nests of similar form and construction, judged to be those of red squirrels (Tamiasciurus hudsonicus), were found in 17 infected trees. Most of the trees with nests were moderately to heavily infected with dwarf mistletoe. All nests were found in witches' brooms caused by dwarf mistletoe. Our finding supports the concept that witches' brooms are an ecologically important addition to the structural and/or functional diversity of forest can- opies-