Technical Report

Characteristics of Marbled Murrelet (Brachyramphus marmoratus) Habitat in Northern California

The Marbled Murrelet (Brachyramphus marmoratus) is a federally threatened seabird and little is known about the species’ nesting ecology, especially in the redwood forests of northern California. Redwood National and State Parks represents a major component of the remaining stands of old-growth redwood forest where Marbled Murrelets nest. We built habitat models to examine differences between used Marbled Murrelet nest sites and random sites and between successful and failed nests in Redwood National and State Parks at three spatial scales: stand, tree, and nest site. The probability of nest-site use increased with distance to the nearest paved road and nests were more likely to be successful in stands with a greater number of downed logs. Nest trees were larger than the average tree size in the stand, but not always the largest tree in the stand. We also measured sound levels at roads and park facilities and estimated the distances from these sites at which anthropogenic noises could no longer be detected. Using a Geographic Information System, we then mapped potential Marbled Murrelet habitat in Redwood National and State Parks, and excluded areas around roads and park facilities that were likely impacted by anthropogenic noise disturbances. Management actions could include protection of these habitat characteristics within old-growth redwood forest, particularly where it occurs far from roads, and minimization of human activities and disturbance within potential Marbled Murrelet habitat in Redwood National and State Parks.