Marbled Murrelets (Brachyramphus marmoratus) are threatened seabirds that are
prone to disturbance both at sea and at old-growth forest nesting areas. I examined
murrelet behavior and activity patterns in forest and marine ecosystems of Oregon.
Diving behavior was studied during the 1995 and 1996 breeding seasons and was
compared to predictions from optimal breathing models, which predicted a strong
relationship between dive times and preceding pause times. Diving patterns appeared to
fit these predictions more in 1996 than 1995 suggesting that diving behavior was affected
more by annual changes in environmental conditions than by physiological constraints on
breathing and diving as predicted by optimal breathing models.
Activity patterns at inland nest sites were monitored on a near-daily basis during
three breeding seasons to assess the relationships between activity and both weather and
date. Daily activity was highly variable within and among sites and years and I observed
greater variability in activity levels than has been previously reported for this species.
Activity varied greatly during all portions of the breeding season and analyses revealed
that weather and date variates explained little of the variability present. It also appeared
that variability in activity during the breeding season was not due entirely to breeding
phenology; however, activity of nonbreeding birds attending nesting stands may
contribute to daily variability.
Inland activity data also were used to assess the feasibility of developing long-term
monitoring strategies based on counts of daily detections. I determined how effectively
various survey strategies estimated measures of daily mean and standard deviation of
detection counts of murrelets within a breeding season. Results indicated that it would be
difficult to obtain reliable estimates of murrelet detections with sampling efforts up to 14
days/season. However, estimates of mean and standard deviation for daily detections
during a breeding season may be reliably estimated to within ± 50% with similar or less
effort. The power of survey strategies to detect annual declines in detections of 25% and
50% were very low and moderate, respectively, except when variability was quite low. / Graduation date: 1999
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36757 |
| Date | 10 November 1998 |
| Creators | Jodice, Patrick G. R., 1961- |
| Contributors | Collopy, Michael W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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