Blue Grouse Feeding on Planted Ponderosa Pine

Abstract

Study of 495 ponderosa pine (Pinus ponderosa) seedlings planted on a burned-over area in central Idaho indicates that foraging by blue grouse (Dendragapus obscurus) may have disfigured some seedlings or inhibited their growth, but did not significantly affect their survival. In June, 1961, an unusually hot fire burned over about 5,700 acres on the Emmett Ranger District of the Boise National Forest. Unseasonably high temperatures and low humidities created a hazard that produced an intensely hot fire, which burned all low ground cover. Virtually all trees, regardless of size, within the perimeter of the fire were killed by either flame or heated air. The approximately 14 million board feet of timber salvaged in the summer and fall of 1961 were made up of ponderosa pine, Douglas fir (Pseudotsuga menziesii), and grand fir (Abies grandis). Contour furrowing of 750 acres for spring planting was carried out concurrently with logging. The country burned over by the fire is extremely rough, typical of the ponderosa pine type in central Idaho-slopes up to 100 percent, shallow soils, rock outcrops, and numerous small ravines. Most of the slopes face to the south and to the west, but other aspects can be found in the area. The elevations vary from 3,240 feet to 3,800 feet above sea level. Ponderosa pine 2 + 0 stock was planted by hand and by machine on 1,000 acres. During the course of the hand planting, Swarth's blue grouse were observed feeding on recently planted seedlings on the upper part of the burn. The birds ate the needles most often, but also fed on the buds and young leaders. In their eagerness for the green leaves the grouse boldly followed the planters as the young trees were set out. This feeding had a demoralizing effect on the planting crews. The foraging flock of some 50 adult grouse fed on the planted trees from the middle of March to about April 20. During this period there was little vegetation available for food other than the planted stock. High survival of planted ponderosa pine frequently is difficult to achieve under the most favorable conditions in this part of the tree's range. Because the effects of feeding on ponderosa pine seedlings by blue grouse were unknown, the authors sought to determine whether this feeding would adversely affect survival of the planted stock. Early in the summer of 1962, 495 trees were marked with stakes for fall examination; 219 of the marked trees had been fed on by grouse. A tally of seedling condition in October yielded the following results: LIVE TREES DEAD TREES (Number) (Percent) (Number) (Percent) Fed on 164 75 55 25 Not fed on 200 72 76 27. A chi-square test of heterogeneity was employed to determine significance of mortality. The results of this test indicated that survival and mortality were independent of whether the trees were fed on. In this study, the damage inflicted during the first year after the burn, when other vegetation was either absent or scarce, is probably the most severe that can be expected. While some of the young trees have suffered disfigurement and in some in-