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Michael W. Collopy

Publications and source records attributed to Michael W. Collopy.

7 recordsLinked to original sources
USGS2001

Using resampling to assess reliability of audio-visual survey strategies for marbled murrelets at inland forest sites

Marbled Murrelets (Brachyramphus marmoratus) are threatened seabirds that nest in coastal old-growth coniferous forests throughout much of their breeding range. Currently, observer-based audio-visual surveys are conducted at inland forest sites during the breeding season primarily to determine nesting distribution and breeding status and are being used to estimate temporal or spatial trends in murrelet detections. Our goal was to assess the feasibility of using audio-visual survey data for such monitoring. We used an intensive field-based survey effort to record daily murrelet detections at seven survey stations in the Oregon Coast Range. We then used computer-aided resampling techniques to assess the effectiveness of twelve survey strategies with varying scheduling and a sampling intensity of 4-14 surveys per breeding season to estimate known means and SDs of murrelet detections. Most survey strategies we tested failed to provide estimates of detection means and SDs that were within A?20% of actual means and SDs. Estimates of daily detections were, however, frequently estimated to within A?50% of field data with sampling efforts of 14 days/breeding season. Additional resampling analyses with statistically generated detection data indicated that the temporal variability in detection data had a great effect on the reliability of the mean and SD estimates calculated from the twelve survey strategies, while the value of the mean had little effect. Effectiveness at estimating multi-year trends in detection data was similarly poor, indicating that audio-visual surveys might be reliably used to estimate annual declines in murrelet detections of the order of 50% per year.

Waterbirds↗
USGS2000

Activity patterns of marbled murrelets in Douglas-fir old-growth forests of the Oregon Coast Range

We monitored activity patterns of Marbled Murrelets ( Brachyramphus marmoratus ) on a near-daily basis using audio-visual surveys during three breeding seasons at five forest stands in the Oregon Coast Range. Three measures of activity were recorded: number of daily detections, number of daily vocalizations, and duration of daily activity. Each measure was highly variable within and among stands and years, and we recorded greater variability than has been previously reported for this species. The three measures of activity were strongly correlated within a day at each survey station, but correlative relationships at temporal and spatial scales greater than this were inconsistent. Activity varied greatly from one day to the next during all portions of the breeding season, and we did not identify any month when variability in activity was consistently higher or lower than any other month. Multivariate analyses revealed that weather and date variates explained little of the variability in daily activity. Given the extreme levels of variability in Marbled Murrelet activity and our lack of understanding as to which factors drive that variability, it is critical that conclusions about activity or behavior not be drawn from data sets not specifically designed to answer the questions of interest.

Oregon↗
USGS1999

Diving and foraging patterns of Marbled Murrelets (Brachyramphus marmoratus): Testing predictions from optimal-breathing models

The diving behavior of Marbled Murrelets (Brachyramphus marmoratus) was studied using telemetry along the Oregon coast during the 1995 and 1996 breeding seasons and examined in relation to predictions from optimal-breathing models. Duration of dives, pauses, dive bouts, time spent under water during dive bouts, and nondiving intervals between successive dive bouts were recorded. Most diving metrics differed between years but not with oceanographic conditions or shore type. There was no effect of water depth on mean dive time or percent time spent under water even though dive bouts occurred in depths from 3 to 36 m. There was a significant, positive relationship between mean dive time and mean pause time at the dive-bout scale each year. At the dive-cycle scale, there was a significant positive relationship between dive time and preceding pause time in each year and a significant positive relationship between dive time and ensuing pause time in 1996. Although it appears that aerobic diving was the norm, there appeared to be an increase in anaerobic diving in 1996. The diving performance of Marbled Murrelets in this study appeared to be affected by annual changes in environmental conditions and prey resources but did not consistently fit predictions from optimal-breathing models.

Canadian Journal of Zoology↗
USGS1999

Bat activity in thinned, unthinned, and old-growth forests in western Oregon

Many aspects of the influences of forest management activities on bats (Chiroptera) in the Pacific Northwest are poorly known. We compared thinned and unthinned forest stands of the same age and old-growth forest stands to determine potential differences in structure and amount of use by bats. We hypothesized that activity levels of bats would differ in stands differing in structure as a result of management history and that activity of bats would be similar in stands of similar structure. We used automated ultrasonic detectors (Anabat II) to record calls of bats in 50-100-year-old thinned and unthinned stands, and in old-growth (a?Y200 yr old) stands in the Oregon Coast Range during the summers of 1994 and 1995. Our median index of bat activity was higher in old-growth than in unthinned stands and higher in thinned than in unthinned stands. We were not able to detect a significant difference between the index of median bat activity for old-growth and thinned stands. More than 90% of identifiable passes were identified as calls from Myotis species. The 3 stand types we examined differed in certain structural characteristics such as density and size of trees, and amount of overstory and understory cover. We concluded that the structural changes caused by thinning may benefit bats by creating habitat structure in young stands that bats are able to use more effectively.

Journal of Wildlife Management↗