Evidence of in male-bias in capture samples of Marbled Murrelets from genetic studies in British Columbia

We report a significant male-bias ( 1.8:1) in Marbled Murrelets (Brachyramp hus marmoratus) captured with floating mist nets during the breeding season over four years (1994-1997) at Theodosia Inlet, Desolation Sound, British Columbia. There was little evidence for marked annual or diurnal variation in male-bias, or for variation due to flight direction of birds when the co ntacted the net (inland vs, out to sea). In contrast, samples of adult and juvenile Marbled Murrelets captured using a night-lighting technique at Des olation Sound in 1997 were not male-biased. We believe that the most likely explanation for our results is that there are sex-specific differences in behavior of Marbled Murrelets during the breeding period. such that more ma les than females are flying between marine foraging and inland nesting area s.