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Geology topics

J.M. Marzluff

Publications and source records attributed to J.M. Marzluff.

10 recordsLinked to original sources
USGS2011

Proactive conservation management of an island-endemic bird species in the face of global change

Biodiversity conservation in an era of global change and scarce funding benefits from approaches that simultaneously solve multiple problems. Here, we discuss conservation management of the island scrub-jay ( Aphelocoma insularis ), the only island-endemic passerine species in the continental United States, which is currently restricted to 250-square-kilometer Santa Cruz Island, California. Although the species is not listed as threatened by state or federal agencies, its viability is nonetheless threatened on multiple fronts. We discuss management actions that could reduce extinction risk, including vaccination, captive propagation, biosecurity measures, and establishing a second free-living population on a neighboring island. Establishing a second population on Santa Rosa Island may have the added benefit of accelerating the restoration and enhancing the resilience of that island's currently highly degraded ecosystem. The proactive management framework for island scrub-jays presented here illustrates how strategies for species protection, ecosystem restoration, and adaptation to and mitigation of climate change can converge into an integrated solution.

California↗
USGS2011

Cougar space use and movements in the wildland-urban landscape of western Washington

The wildland-urban interface lies at the confluence of human-dominated and wild landscapes, creating a number of management and conservation challenges. Because wildlife ecology, behavior, and evolution at this interface are shaped by both natural and human phenomena, this requires greater understanding of how diverse factors affect ecosystem and population processes. We illustrate the challenge of understanding and managing a frequent and often undesired inhabitant of the wildland-urban landscape, the cougar (Puma concolor). In wildland and residential areas of western Washington State, USA, we captured and radiotracked 27 cougars to model space use and understand the role of landscape features in interactions (sightings, encounters, and depredations) between cougars and humans. Resource utilization functions (RUFs) identified cougar use of areas with features that were probably attractive to prey, influential on prey vulnerability, and associated with limited or no residential development. Early-successional forest (+), conifer forest (+), distance to road (-), residential density (-), and elevation (-) were significant positive and negative predictors of use for the population, whereas use of other landscape features was highly variable. Space use and movement rates in wildland and residential areas were similar because cougars used wildland-like forest patches, reserves, and corridors in residential portions of their home range. The population RUF was a good predictor of confirmed cougar interactions, with 72% of confirmed reports occurring in the 50% of the landscape predicted to be medium-high and high cougar use areas. We believe that there is a threshold residential density at which the level of development modifies the habitat but maintains enough wildland characteristics to encourage moderate levels of cougar use and maximize the probability of interaction. Wildlife managers trying to reduce interactions between cougars and people should incorporate information on spatial ecology and landscape characteristics to identify areas with the highest overlap of human and cougar use to focus management, education, and landscape planning. Resource utilization functions provide a proactive tool to guide these activities for improved coexistence with wildlife using both wildland and residential portions of the landscape. ??2011 by the Ecological Society of America.

Ecological Applications↗
USGS2001

Influence of military activities on raptor abundance and behavior

We investigated the influence of military training on the abundance and behavior of raptors at a military training area in the Snake River Birds of Prey National Conservation Area in Idaho during the breeding seasons of 1991a??1994. Raptor counts on military training ranges did not differ when we compared all training days to all non-training days. However, during one period of intensive military training in one breeding season, raptor counts were lower during training than on non-training days. During training, Northern Harriers (Circus cyaneus) did not alter their behavior on training days. In years when prey numbers were low, falcons, hawks, and eagles perched and flew at low levels less often and flew at higher altitudes more often during training than they did when training did not occur. We observed fewer prey capture attempts on ranges on days with training than on days without training. Specific types of military training activity affected counts of raptors on ranges. The lowest raptor counts were associated with firing of artillery, small arms, and main turret guns or machine guns on tanks. Raptor counts associated with tank preparation (i.e., assembling and loading ammunition), driving, laser training, and convoy traffic were similar to non-training periods.

The Condor↗
USGS2000

Cryptic genetic variation and paraphyly in ravens

Widespread species that are morphologically uniform may be likely to harbour cryptic genetic variation. Common ravens ( Corvus corax ) have an extensive range covering nearly the entire Northern Hemisphere, but show little discrete phenotypic variation. We obtained tissue samples from throughout much of this range and collected mitochondrial sequence and nuclear microsatellite data. Our study revealed a deep genetic break between ravens from the western United States and ravens from throughout the rest of the world. These two groups, the ‘California clade’ and the ‘Holarctic clade’ are well supported and over 4% divergent in mitochondrial coding sequence. Microsatellites also reveal significant differentiation between these two groups. Ravens from Minnesota, Maine and Alaska are more similar to ravens from Asia and Europe than they are to ravens from California. The two clades come in contact over a huge area of the western United States, with mixtures of the two mitochondrial groups present in Washington, Idaho and California. In addition, the restricted range Chihuahuan raven ( Corvus cryptoleucus ) of the south–west United States and Mexico is genetically nested within the paraphyletic common raven. Our findings suggest that the common raven may have formerly consisted of two allopatric groups that may be in the process of remerging.

Proceedings of the Royal Society B: Biological Sci↗
USGS1999

Effects of fire on golden eagle territory occupancy and reproductive success

We examined effects of fire on golden eagle (Aquila chrysaetos) territory occupancy and reproductive success in southwestern Idaho because wildfires since 1980 have resulted in large-scale losses of shrub habitat in the Snake River Plain. Success (percentage of pairs that raised young) at burned territories declined after major fires (P = 0.004). Pairs in burned areas that could expand into adjacent vacant territories were as successful as pairs in unburned territories and more successful than pairs in burned territories that could not expand. Success at extensively burned territories was lowest 4-6 years after burning but increased 4-5 years later. The incidence and extent of fires did not help predict territories that would have low occupancy and success rates in postburn years. The presence of a vacant neighboring territory and the amount of agriculture and proportion of shrubs within 3 km of the nesting centroid best predicted probability of territory occupancy. Nesting success during preburn years best predicted the probability of a territory being successful in postburn years. Burned territories with high success rates during preburn years continued to have high success rates during postburn years, and those with low success in preburn years continued to be less successful after burning. In areas where much shrub habitat has been lost to fire, management for golden eagles should include active fire suppression and rehabilitation of burned areas.

Journal of Wildlife Management↗
USGS1997

The influence of habitat, prey abundance, sex, and breeding success on the ranging behavior of Prairie Falcons

We studied the ranging behavior and habitat selection of radio-tagged Prairie Falcons (Falco mexicanus) during the breeding season in southwestern Idaho. The distribution and numbers of Townsend's ground squirrels (Spermophilus townsendii), the primary prey of Prairie Falcons in our study area, varied in response to drought during the study period. Prairie Falcons ranged over large areas (ca. 300 km2) and increased their foraging ranges in response to declining ground squirrels. Reptiles and birds were preyed upon most frequently when squirrels were rare. Males and females differed little in their use of space. Successful pairs ranged over smaller areas than non-nesters and unsuccessful pairs. Falcons nesting near habitat most suitable for ground squirrels ranged over smaller areas than those nesting farther from such habitat. Home ranges contained significantly more winterfat (Ceratoides lanata) and native perennial grasses (especially Poa secunda), and significantly less salt desert shrubs and exotic annual grasses than expected based on availability. Salt desert shrubs were found less than expected, based on availability in core areas within home ranges. Selection for winterfat and bluegrass in core areas was contingent upon selection at the larger scale of the home range; falcons with home ranges containing more winterfat and bluegrass than expected based on availability were less selective in their placement of core areas with respect to these habitats. We believe salient features of Prairie Falcon home ranges result largely from patchy distribution of landscape features associated with different densities and availabilities of Townsend's ground squirrels.

The Condor↗
USGS1997

Spatial use and habitat selection of golden eagles in southwestern Idaho

We measured spatial use and habitat selection of radio-tagged Golden Eagles ( Aquila chrysaetos ) at eight to nine territories each year from 1992 to 1994 in the Snake River Birds of Prey National Conservation Area. Use of space did not vary between years or sexes, but did vary among seasons (home ranges and travel distances were larger during the nonbreeding than during the breeding season) and among individuals. Home ranges were large, ranging from 190 to 8,330 ha during the breeding season and from 1,370 to 170,000 ha outside of the breeding season, but activity was concentrated in small core areas of 30 to 1,535 ha and 485 to 6,380 ha during the breeding and nonbreeding seasons, respectively. Eagles selected shrub habitats and avoided disturbed areas, grasslands, and agriculture. This resulted in selection for habitat likely to contain their principal prey, black-tailed jackrabbits ( Lepus californicus ). Individuals with home ranges in extensive shrubland (n = 3) did not select for shrubs in the placement of their core areas or foraging points, but individuals in highly fragmented or dispersed shrublands (n = 5) concentrated their activities and foraged preferentially in jackrabbit habitats (i.e. areas with abundant and large shrub patches). As home ranges expanded outside of the breeding season, individuals selected jackrabbit habitats within their range. Shrubland fragmentation should be minimized so that remaining shrub patches are large enough to support jackrabbits.

The Auk↗
USGS1997

Productivity of golden eagles wearing backpack radiotransmitters

We examined the association between the presence of backpack radiotransmitters and Golden Eagle ( Aquila chrysaetos ) reproduction (percentage of occupied territories producing young, and number of nestlings produced) over three years. The association between radio-tagging and nesting success and the number of nestlings produced varied significantly among years. A negative association with tagging was observed in one of three years, which coincided with low prey (jackrabbit) populations and a cold spring. However, small sample size and breeding by subadults may confound this result.

Journal of Raptor Research↗
USGS1996

Influence of radio transmitters on prairie falcons (Falco mexicanus)

We examined the effects of backpack radio transmitters on Prairie Falcon (Falco mexicanus) reproduction (percentage of occupied territories producing young and number of nestlings produced) over four years. In addition, we observed falcon aeries during brood-rearing to determine attendance at the nest and in the territory, prey delivery rates, and prey composition. We found no effect of radio tagging on Prairie Falcon productivity (nesting success and brood size) among years, although productivity varied significantly among years. The sex of the falcon tagged did not affect productivity. Radio-tagged members of pairs did not differ significantly from un-tagged members of pairs in territory attendance, nest attendance, prey delivery rates, or caching rates. Nestlings raised by radio-tagged parents attained masses similar to those reared by control parents. During low prey years, radio-tagged males brought a greater proportion of small birds and reptiles, and fewer mammals to the nest area than control males.

Journal of Field Ornithology↗