Nesting behavior of Marbled Murrelets Brachyramphus marmoratus in Washington and British Columbia

Marbled Murrelets are threatened seabirds that nest predominantly in old-growth forests in the southern part of their western North America range. Little is known about causes of nest failure, timing of parental visits, and nest reuse because it is difficult to locate and monitor nests of this cryptic species. We used radio telemetry to locate murrelet nests from 2004 to 2008 in northwestern Washington and southeastern British Columbia. We monitored four nests with video cameras to document causes of nest failure, and we visited 15 nests after the nesting season to infer nest fate. We also monitored six active nests with telemetry data loggers to determine the timing of parental visits and eight previous-year nests to determine nest reuse. Among 20 nests, four successfully fledged and 16 failed. Among failed nests, 10 failed from unknown causes and the remaining six failed from non-predatory causes. Parental visits during the incubation period occurred exclusively before dawn (100 % of 32 visits), whereas visits during the nestling period (n = 73) occurred during the morning (70 %), afternoon (1 %), and evening (29 %). Among eight nests monitored for reuse, we observed two cases of nest reuse and two cases in which nests were briefly visited by murrelets in later years but were not reused for nesting.