At-sea Activity and Diving Behavior of a Radio-tagged Marbled Murrelet in Central California

Radio-telemetry was used to continuously monitor the at-sea activity of an adult Marbled Murrelet (Brachyramphus marmoratus) nesting in Santa Cruz County, California. From 05.39 h on 28 May 1997, to 05.14 h on 29 May 1997, the murrelet was followed by tracking teams at Año Nuevo Bay. Between 05.44 h and 20.19 h on 28 May, the bird engaged in eleven dive bouts, with a mean duration of 18.8 ± 5.4 min. Mean dive duration was 24.8 ± 15.7 s; mean surface between dives was 15.2 ± 12.7 s. No dives were initiated after 20.19 h. The bird spent 12.3% of the at-sea period and 23.4% of daylight hours engaged in diving bouts. This relatively small amount of time spent diving allows for considerable flexibility in activity budget.