McIntyre C.L.,National Park Service
Journal of Raptor Research | Year: 2012
Documenting the year-round movements and factors affecting the survival of wide-ranging birds is essential for developing effective conservation strategies. This is especially true for long-distance migratory species that spend much of their lives away from their breeding areas. Encounters of banded birds have provided information on the movements and survival of many bird species. More recently, telemetry studies provided new information on movements and survival of migratory birds. Golden Eagles (Aquila chrysaetos) raised in the higher latitudes of northwestern North America are usually migratory, but little is known about their year-round movements or survival. From 1988 to 2009, I banded 307 Golden Eagle nestlings in and near Denali National Park and Preserve in interior Alaska. From 1997 to 1999, I also deployed 90-g satellite transmitters on 48 of these eagles just before they fledged. Ten of the 307 banded eagles (3%) were encountered after the banding event, including five within 1 yr of banding. All encounters with banded eagles were >800 km from the banding location outside Alaska during winter or the migration season. All banded eagles were encountered <2 km from a road or human settlement and the primary sources of mortality were electrocution and shooting. In contrast, all recoveries of dead radio-tagged eagles (14) were >5 km from a road, and post-mortem necropsy indicated that all but one of these eagles died from starvation. Locations of banded eagles encountered in winter ranged from southern Alberta to north-central Mexico. Relocations of radio-tagged eagles in winter ranged from central Alberta to southeastern New Mexico. These results, despite small sample sizes, demonstrate how different marking and tracking tools can produce different results regarding the sources of mortality and the wintering range of Golden Eagles from the same study area. © 2012 The Raptor Research Foundation, Inc.
Primack R.B.,Boston University |
Miller-Rushing A.J.,National Park Service
BioScience | Year: 2012
Historical records are an important resource for understanding the biological impacts of climate change. Such records include naturalists' journals, club and field station records, museum specimens, photographs, and scientific research. Finding records and overcoming their limitations are serious challenges to climate change research. In the present article, we describe efforts to locate data from Concord, Massachusetts, and provide a template that can he replicated in other locations. Analyses of diverse data sources, including observations made in the 1850s by Henry David Thoreau, indicate that climate change is affecting the phenology, presence, and abundance of species in Concord. Despite recent work on historical records, many sources of historical data are underutilized. Analyses of these data may provide insights into climate change impacts and techniques to manage them. Moreover, the results are useful for communicating local examples of changing climate conditions to the public. © 2012 by American Institute of Biological Sciences. All rights reserved.
Collins B.D.,U.S. Geological Survey |
Stock G.M.,National Park Service
Nature Geoscience | Year: 2016
Exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cliff in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the efficacy of other, more typical rockfall triggers. © 2016 Macmillan Publishers Limited. All rights reserved.
Duriscoe D.M.,National Park Service
Publications of the Astronomical Society of the Pacific | Year: 2013
Anthropogenic sky glow (a result of light pollution) combines with the natural background brightness of the night sky when viewed by an observer on the earth's surface. In order to measure the anthropogenic component accurately, the natural component must be identified and subtracted. A model of the moonless natural sky brightness in the V-band was constructed from existing data on the Zodiacal Light, an airglow model based on the van Rhijn function, and a model of integrated starlight (including diffuse galactic light) constructed from images made with the same equipment used for sky brightness observations. The model also incorporates effective extinction by the atmosphere and is improved at high zenith angles (>80°) by the addition of atmospheric diffuse light. The model may be projected onto local horizon coordinates for a given observation at a resolution of 0.05° over the hemisphere of the sky, allowing it to be accurately registered with data images obtained from any site. Zodiacal Light and integrated starlight models compare favorably with observations from remote dark sky sites, matching within ± 8 nL over 95% of the sky. The natural airglow may be only approximately modeled, errors of up to ± 25 nL are seen when the airglow is rapidly changing or has considerable character (banding); ± 8 nL precision may be expected under favorable conditions. When subtracted from all-sky brightness data images, the model significantly improves estimates of sky glow from anthropogenic sources, especially at sites that experience slight to moderate light pollution. © 2013. The Astronomical Society of the Pacific. All rights reserved.
McDonald H.G.,National Park Service
Journal of Mammalian Evolution | Year: 2012
The rotation of the pes or pedolateral stance in the extinct ground sloths so the body weight of the animal is primarily supported by the fifth metatarsal and the calcaneum occurred independently at least three times and is present in the Megatheriidae, Nothrotheriidae, and Mylodontidae. In contrast, the pes in the Megalonychidae more closely resembles the primitive eutherian pattern. The pedolateral rotation of the pes thus represents an excellent example of parallel evolution in a closely related group of mammals. While the rotation of the foot occurs as a functional complex resulting in the modification of many bones in the pes, the astragalus is the one bone that shows the highest degree of departure from the primitive mammalian condition and the most distinctive changes in morphology. The morphological transition from a plantigrade foot as occurs in xenarthran anteaters and is essentially retained in the megalonychid sloths to the highly derived condition seen in the megathere, nothrothere, and mylodont sloths follows a similar pattern in all groups but there is still significant variation in the foot structure between the lineages. Despite these variations there are consistent patterns of change in the astragalus in all groups related to the progressive rotation of the pes and a change from dorso-plantar flexion and extension to a medio-lateral rotation of the pes relative to the tibia. © 2012 Springer Science+Business Media, LLC (outside the USA).