24 research outputs found
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Factors Affecting Incubation Patterns and Sex Roles of Black Oystercatchers in Alaska
Studies examining the effects of human disturbance on avian parental behavior and reproductive
success are fundamental to bird conservation. However, many such studies fail to also consider the influence of
natural threats, a variable environment, and parental roles. Our work examines interactive relationships of cyclical
(time of day, tide, temperature, seasonality) and stochastic (natural/human disturbance) processes with incubation
patterns (attendance, bout lengths, recess rates) of the Black Oystercatcher (Haematopus bachmani), a shorebird
of conservation concern. We used 24-hr-per-day video monitoring of 13 molecularly sexed breeding pairs to
systematically examine incubation, revealing previously undocumented information that may inform conservation
practices for the genus. Seven of 22 video-monitored nests failed, primarily from egg depredation by nocturnal
mammals. Analyses of 3177 hr of video footage indicated a near doubling of incubation-bout lengths at night,
corresponding to the increased risk of nighttime egg predation. Females had higher overall nest attendance (54%
vs. 42%) and longer mean incubation bouts than did males (88 min vs. 73 min). Uninterrupted incubation bouts
were over twice as long as bouts interrupted by disturbance. Incubating males departed nests substantially more
frequently because of nest-area disturbances than did females in one but not both years of our study. Our findings
suggest that the sexes incubate in different but complementary patterns, facilitating efficient egg care in a dynamic
environment with several nest threats. We emphasize the importance of considering natural influences when human
threats to shorebird reproductive behavior and success are evaluated.Keywords: Black Oystercatcher, Disturbance, Incubation behavior, Prince William Sound, sex roles, Video monitoring, Nest failure, Haematopu
Region-Wide Ecological Responses of Arid Wyoming Big Sagebrush Communities to Fuel Treatments
If arid sagebrush ecosystems lack resilience to disturbances or resistance to annual invasives, then alternative successional states dominated by annual invasives, especially cheatgrass (Bromus tectorum L.), are likely after fuel treatments. We identified six Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle & Young) locations (152–381 mm precipitation) that we believed had sufficient resilience and resistance for recovery. We examined impacts of woody fuel reduction (fire, mowing, the herbicide tebuthiuron, and untreated controls, all with and without the herbicide imazapic) on short-term dominance of plant groups and on important land health parameters with the use of analysis of variance (ANOVA). Fire and mowing reduced woody biomass at least 85% for 3 yr, but herbaceous fuels were reduced only by fire (72%) and only in the first year. Herbaceous fuels produced at least 36% more biomass with mowing than untreated areas during posttreatment years. Imazapic only reduced herbaceous biomass after fires (34%). Tebuthiuron never affected herbaceous biomass. Perennial tall grass cover was reduced by 59% relative to untreated controls in the first year after fire, but it recovered by the second year. Cover of all remaining herbaceous groups was not changed by woody fuel treatments. Only imazapic reduced significantly herbaceous cover. Cheatgrass cover was reduced at least 63% with imazapic for 3 yr. Imazapic reduced annual forb cover by at least 45%, and unexpectedly, perennial grass cover by 49% (combination of tall grasses and Sandberg bluegrass [Poa secunda J. Presl.]). Fire reduced density of Sandberg bluegrass between 40% and 58%, decreased lichen and moss cover between 69% and 80%, and consequently increased bare ground between 21% and 34% and proportion of gaps among perennial plants &spigt; 2 m (at least 28% during the 3 yr). Fire, mowing, and imazapic may be effective in reducing fuels for 3 yr, but each has potentially undesirable consequences on plant communities
Recommended from our members
Region-Wide Ecological Responses of Arid Wyoming Big Sagebrush Communities to Fuel Treatments
If arid sagebrush ecosystems lack resilience to disturbances or resistance to annual invasives, then alternative successional states
dominated by annual invasives, especially cheatgrass (Bromus tectorum L.), are likely after fuel treatments. We identified six
Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle & Young) locations (152–381 mm precipitation) that
we believed had sufficient resilience and resistance for recovery. We examined impacts of woody fuel reduction (fire, mowing,
the herbicide tebuthiuron, and untreated controls, all with and without the herbicide imazapic) on short-term dominance of
plant groups and on important land health parameters with the use of analysis of variance (ANOVA). Fire and mowing reduced
woody biomass at least 85% for 3 yr, but herbaceous fuels were reduced only by fire (72%) and only in the first year.
Herbaceous fuels produced at least 36% more biomass with mowing than untreated areas during posttreatment years. Imazapic
only reduced herbaceous biomass after fires (34%). Tebuthiuron never affected herbaceous biomass. Perennial tall grass cover
was reduced by 59% relative to untreated controls in the first year after fire, but it recovered by the second year. Cover of all
remaining herbaceous groups was not changed by woody fuel treatments. Only imazapic reduced significantly herbaceous cover.
Cheatgrass cover was reduced at least 63% with imazapic for 3 yr. Imazapic reduced annual forb cover by at least 45%, and
unexpectedly, perennial grass cover by 49% (combination of tall grasses and Sandberg bluegrass [Poa secunda J. Presl.]). Fire
reduced density of Sandberg bluegrass between 40% and 58%, decreased lichen and moss cover between 69% and 80%, and
consequently increased bare ground between 21% and 34% and proportion of gaps among perennial plants >2 m (at least 28%
during the 3 yr). Fire, mowing, and imazapic may be effective in reducing fuels for 3 yr, but each has potentially undesirable
consequences on plant communities.Keywords: Imazapic, Bromus tectorum, Fire, Resistance and resilience, Mowing, Tebuthiuro
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Estimating wind-turbine-caused bird and bat fatality when zero carcasses are observed
Many wind-power facilities in the United States have established effective monitoring programs to determine turbine-caused fatality rates of birds and bats, but estimating the number of fatalities of rare species poses special difficulties. The loss of even small numbers of individuals may adversely affect fragile populations, but typically, few (if any) carcasses are observed during monitoring. If monitoring design results in only a small proportion of carcasses detected, then finding zero carcasses may give little assurance that the number of actual fatalities is small. Fatality monitoring at wind-power facilities commonly involves conducting experiments to estimate the probability (g) an individual will be observed, accounting for the possibilities that it falls in an unsearched area, is scavenged prior to detection, or remains undetected even when present. When g ~0.45. Further, we develop extensions for temporal replication that can inform prior distributions of M and methods for combining information across several areas or time periods. We apply the method to data collected at a wind-power facility where scheduled searches yielded X = 0 raptor carcasses.This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecapKeywords: prior, Bayes' theorem, imperfect detection, wind power, superpopulation, rare species, posterior, endangered specie
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Habitat selection by juvenile Swainson’s thrushes (Catharus ustulatus) in headwater riparian areas, Northwestern Oregon, USA
Lower order, non-fish-bearing streams, often termed ‘‘headwater streams’’, have received minimal
research effort and protection priority, especially in mesic forests where distinction between riparian
and upland vegetation can be subtle. Though it is generally thought that breeding bird abundance is
higher in riparian zones, little is known about species distributions when birds are in their juvenile stage
– a critical period in terms of population viability. Using radio telemetry, we examined factors affecting
habitat selection by juvenile Swainson’s thrushes during the post-breeding period in headwater basins in
the Coast Range of Oregon, USA. We tested models containing variables expected to influence the amount
of food and cover (i.e., deciduous cover, coarse wood volume, and proximity to stream) as well as models
containing variables that are frequently measured and manipulated in forest management (i.e., deciduous
and coniferous trees separated into size classes). Juvenile Swainson’s thrushes were more likely to
select locations with at least 25% cover of deciduous, mid-story vegetation and more than 2.0 m3/ha of
coarse wood within 40 m of headwater streams. We conclude that despite their small and intermittent
nature, headwater streams and adjacent riparian areas are selected over upland areas by Swainson’s
thrush during the postfledging period in the Oregon Coast Range.Keywords: Riparian, Swainson’s thrush, Juvenile songbird, Headwater stream, Habitat selectio
Appendix A. A summary of detections of birds during the pre-treatment year (1994), post-treatment years (1995–2000), and all years combined, as well as a complete species list.
A summary of detections of birds during the pre-treatment year (1994), post-treatment years (1995–2000), and all years combined, as well as a complete species list
Appendix B. Calculations of overall probability of detection g at Foote Creek Rim (Young et al. 2003).
Calculations of overall probability of detection g at Foote Creek Rim (Young et al. 2003)
Appendix A. Expectation and variance of overall probability of detection g across multiple independent areas or time periods.
Expectation and variance of overall probability of detection g across multiple independent areas or time periods