The Interrelationships of Logging, Birds, and Timber Regeneration in the Douglas-Fir Region of Northwestern California

Abstract

tntensive logging of a virgin stand of Douglasfir (Pscidotsizga mnienziesii) began in 1950 in the inner cast ranges of northwestern California. Most timber is being clear cut in blocks of from 10 to 20 acres. Intervening blocks of roughly equal size are left for a later cutting and meanwhile serve as seed sources for the cutovers. Initial efforts to seed coniferous trees on these blocks by artificial or natural means have been discouraging. Rodents and other seed-eating animals flourishl after logging, and play a major role in retarding or preventing regeneration. The subject of animals as destroyers of conifer seed has been discussed l)y Smith and Aldous (1947), who reviewed the literature and listed all birds and mammals known to eat coniferous seed in the United States. Rodents, particularly mice of the genus Peroniivscits, have long been recognized as the chief consumers. Studies of the local distribution and food of two species of Pcronzysclus on timberland in California have beei7 made by J arneson (1951 and 1952). The responses of small mammal populations to logging of D)ouglas-fir were stuclied by Tevis (1956). Further information on animal factors that hinder reforestation is needed by the forester and an uinderstanding of how logging alters the fauna is of value to the ecologist and land manager. Toward these ends, tEis study of forest birds was made in cooperation \with the California Forest and Range Experiment Station on the Six Rivers National Forest near Salyer in Trinity and Humboldt Counties, California. The purpose of the investigation was to determinee changes in species composition, numbers, food habits, and activities of bird populatio1ls immediately after the forest is logged and during the first few years after logging when regeneration of timber is most en(langered by biological and physical adversity. The effect of environmental changes on populations of forest birds have been studied by Lack (1933, 1939, and 1951) in English pine plantations, and by Odum (1950) in successional stages towarcl climax hardwood and hemlock forest of the Highlands Plateau in North Carolina. Studies by Turcek (1952 and 1956) were concerned with bird populations of spruce and other forest types in Czechoslovakia. STUDY AREAS