ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

forests are cavity nesters. They are especially sensitive to timber harvesting
practices because of their need for nesting and roosting cavities within snags or
live trees with heartrot. This group of birds is largely insectivorous. Thus
harvesting and residue utilization practices that affect insect populations also
influence cavi ty-nesting bird populations. The birds affect insect numbers through
predation and may maintain endemic population levels of some forest insects, or at
1 east 1 engthen interval s between epidemics (Beebe 1974). But consideration of cavity
nesters, or any other 1 ife form, should not be confined to possible economic benefits
of the speci.es or group (Ehrenfeld 1974). Ecological , scientific, and esthetic values
also are essential factors, though not easily quantified. The fact that cavity nest-
ers are a natural part of forest ecosystems is by itself sufficient reason for forest
managers to give them careful consideration. Perpetuation of cavity nesters within
a forest subjected to harvesting is possible only with careful planning based on
know1 edge of the environmental consequences of the proposed manipulation.
Conner and Crawford (1 974) studied woodpecker foraging in Appalachian cl earcuts.
Conner et a1 . (1975) evaluated the influence of cutting on woodpecker nesting habitat
in Virginia. Other studies have dealt with the impact of cutting on both open and
cavi ty-nesting birds: Ha ar (1 960) in Cal ifornia; Franzreb (1978) in Arizona;
Titterington et a1. (19793 in Maine; Kessler (1979) in Alaska.
The study described in this report was designed to provide some of the basic
information needed by managers concerned with the welfare of cavity nesters in
western larch/Douglas-fir1 forests. Study objectives were: 1) to evaluate the in-
fluence of alternate timber harvesting and residue utilization practices on the nest-
ing and feeding activities of cavity-nesting birds; 2) to quantify variables descrip-
tive of the timber, character of dead material, the area, and of harvesting prescrip-
tion and residue utilization that significantly influence continued use by cavity
nesters; 3) to provide recommendations for modifying harvesting and utilization prac-
tices to minimize adverse impacts on these species.
In this study students and I have concentrated on "primary" cavity nesters, the
woodpeckers (fig. I), all of which are capable of excavating their own nesting cavi-
ties within trees. Most secondary cavity-nesters (e.g., bluebirds, small owls
(fig. 2), some swallows and ducks) must rely on the woodpeckers or on natural decay
processes for production of nest and roost cavities.
'scientific names are listed in the Appendix.