Predation risks for nesting birds in fragmented coast redwood forest

Loss and fragmentation of habitat remain the principal threats to most temp erate zone birds in the United States. The coast redwood (Sequoia sempivire ns) forest ecosystem has been highly fragmented. The purpose of this study was to evaluate predation risk in relation to nest type, distance from the forest edge, edge type, and nest concealment. The study was conducted in ol d-growth and mature second-growth coast redwood forest stands in northern C alifornia from May to August 1997. Forty-one transects were established ext ending from the edge to 150 m into the forest interior surrounded by 5 edge types: suburb, young forest, prairie, river, and road. A total of 562 arti ficial nests (half arboreal nests and half ground nests) with quail eggs we re placed at 25-m intervals along the transects and were checked after 7 an d 13 days. The probability of predation decreased with increasing distance from the edge, was higher for arboreal nests than ground nests, and was hig her later in the nesting season (P < 0.05 for all comparisons). Predation w as significantly higher for prairie edge than all other edge types after 7 days (P < 0.05), and was significantly higher than suburb edge after 14 day s (P < 0.05). We failed to detect an effect of nest concealment on the risk of predation after 7 days (P = 0.588) and 14 days (P = 0.052). The probabi lity of predation as a function of distance from the forest edge did not in dicate a threshold pattern, but rather a gradual decline so that a distance of 115 meters from the edge was required before the probability of predati on declined by halt Based on this study we recommend that edge effects be t aken into consideration when planning for the conservation of bird species in old-growth and nature second-growth coast redwood forests.