Discovery and Observations of Two Tree Nests of the Marbled Murrelet

Two nests of the Marbled Mm-relet (Brachyramphus marmoratus) were found in old-growth (300 + years) Douglas-fir (Pseudotsuga menziesiz] trees in Big Basin Redwoods State Park, Santa Cruz County, California.These were the third and fourth known North American tree nests, and the first to be found by searching from the ground without the use of radio-telemetry.Ground-search techniques for finding nests are presented.Both nests were in the incubation stage when found.Each was observed from a distance for 15 days and 34 days, respectively.Incubation shifts lasted 24 hr with the adults exchanging duties at dawn.Flight behavior near the nest is described.Corvid predation caused both nests to fail, and may be a problem where mm-relets nest in areas of high human usage.After nest failure, each tree was climbed.Both nests were located in the inner canopy, mid-crown portion of the trees.Nest branches were large, moss-covered, horizontal branches that were well shaded.One nest was a previously undescribed type of constructed nest made up of small Douglas-fir twigs and foliose lichens.The other nest was a natural depression in a moss-covered limb.Eggshell fragments were similar to previously described eggs.Nest site characteristics are compared to characteristics of the other known Marbled Murrelet tree nests.