Technical Report

Observations of Incubation in Year 8 of a Long-term Monitoring Effort at a Marbled Murrelet Nest in Northern California

Marbled Murrelets (Brachyramphus marmoratus) have been endangered in the state of California since 1992 and continue to decline across their range. In recent years this has been primarily due to predation of eggs and young at the nest. Very few studies of murrelets have occurred at their nest due to the difficulty of locating and observing active nests. In northern California, a video camera has been installed at one nest since 2001 and each nesting attempt has been recorded. The 2008 nesting season is reported. In 2008, an egg was laid and survived 29 days before being predated by a Steller’s Jay (Cyanocitta stelleri). Each morning between egg lay and nest failure, one murrelet departed from the nest 41 min 43 sec±56 sec (x¯ ±SE) following sunrise and the other member of the pair arrived at the nest 41 min 53 sec±66 sec after sunrise. When arrival occurred before departure from the nest, both members of the pair were present at the same time; this co-attendance occurred for a total duration of 2min 2 sec across the entire recorded incubation. Three instances of egg neglect were recorded within the first 9 days of incubation, totaling 24 hrs 11 min 20 sec. While incubating at the nest, murrelets remained motionless (with the exception of blinking) 98.7±1.1% of the time. Murrelets would turn their egg 1.8±5.2 times per hr, primarily using their feet. More egg turns occurred when leaves and branches surrounding the nest-site moved because of the wind. Other behaviors were also recorded including preening, head lifting, and gaping. A rarely reported behavior, described here as feather compression, was also observed regularly and may have been related to the presence of threats near the nest. Considering all nesting attempts at this site, this nest has successfully fledged young 25% of the years. Further, this nest-branch has been used in 6 of 8 years. Finally, at least one member of this breeding pair was a minimum of 9-11 years old.