Using multiple methods to describe breeding, stress response, and disturbance of marbled murrelets (Brachyramphus marmoratus)

I investigated the breeding biology of Marbled Murrelets using (a) vitellogenin (VTG) analyses, (b) brood patch (BP) scores (thought to imply incubating adults), and (c) radio telemetry data. VTG analyses allowed description of the 5-month breeding season for Marbled Murrelets, the timing of which did not vary between years (1999--2000). Of the females caught between April to July (the 'egg-production period'), 55% were producing eggs. Using brood patches (BP) to infer reproductive status is an approach that should be used cautiously: 53% Marbled Murrelets caught with fully-developed BP never incubated, and likewise, 50% of fecund, radio-tagged females never incubated (failed incubators?). Of a sample of fecund females, 40% started incubation about 15 days later than expected (delayed incubators?). This suggests large numbers of birds that failed to start incubation, for reasons that were not clear. While investigator disturbance explained some cases, seasonal date also had an effect on breeding success. (Abstract shortened by UMI.).