Statistical power analysis can be used to increase the efficiency of research efforts and clarify results. Power is most valuable in design or planning phases efforts. Such prospective (a priori) analyses guide estimate number samples necessary achieve a high probability detecting biologically significant effects. Retrospective posteriori) has been advocated as method information about hypothesis tests that were not rejected. However, estimating for null hypotheses rejected with effect size...

To assess the consequences of increased recreational activity in wilderness areas, we studied effects human on breeding behavior Bald Eagles (Haliaeetus leucocephalus) interior Alaska. Activity budgets eagles changed considerably when humans were camped for 24 h at a distance 100 m from nests (treatment) compared to they 500 (control) (P = 0.0036). With near nests, adult decreased time preened (percentage change control treatment −53%), slept (−56%), maintained (−50%), and fed themselves...

Abstract Invasions by nonnative plants have changed the structure of many terrestrial ecosystems and altered important ecological processes such as fire, dominant driver in grassland ecosystems. Reestablishing fire has been proposed a mechanism to restore dominance native grasslands invaded plants, yet may function differently these systems, potentially affecting animals novel ways. To assess whether invasions alter effects on animals, we performed manipulative experiment semi‐desert...

Understanding how natural and anthropogenic processes affect population dynamics of species with patchy distributions is critical to predicting their responses environmental changes. Despite considerable evidence that demographic rates dispersal patterns vary temporally in response an array biotic abiotic processes, few applications metapopulation theory have sought explore factors explain spatiotemporal variation extinction or colonization rates. To facilitate exploring these factors, we...

Human activity in caves can affect bats adversely, especially that assemble maternity colonies where appropriate roosts are restricted to areas with a narrow range of microclimates necessary raise young. We assessed behavioral responses colony about 1,000 cave myotis (Myotis velifer) experimental tours by manipulating 3 factors: size tour groups, whether groups talked, and combination light intensity color used illuminate trails. also considered the effects distances between bat group as...

Along narrow rivers, spatial restriction of human use based on wildlife responses can effectively eliminate the entire river corridor from use. Therefore, if by both and humans is a goal, an alternative management strategy necessary. We measured flush response rate distance breeding nonbreeding Bald Eagles (Haliaeetus leucocephalus) to recreational boating along Gulkana River in interior Alaska 1989 1992. Eagle our nonmotorized boat were governed context within which human‐eagle encounters...

To determine if contaminants contributed to low hatching success of ospreys (Pandion haliaetus) nesting near Delaware Bay, we compared levels organochlorines, mercury, and lead in addled randomly collected eggs potential prey from Bay a successful population along the Atlantic Coat (<80 km colony), tributary Bay. Eggs contained significantly higher DDE, DDD, PCB's, dieldrin, heptachlor epoxide than did Coast (P<0.008) also had thinner eggshells (P=0.04); Maurice River intermediate...

We quantified movements, spacing, and activity of Sonoran Mud Turtles (Kinosternon sonoriense) in interrupted mountain streams southern Arizona over an 18-year period using capture–recapture sampling radiotelemetry. Movement patterns turtles depended on water availability varied by their sex size. Although considered almost entirely aquatic Arizona, mud estivated terrestrially during periods extreme drought. After the onset summer rains, increased frequency with which they moved between...

Abstract: Effective conservation requires strategies to monitor populations efficiently, which can be especially difficult for rare or elusive species where field surveys require high effort and considerable cost. Populations of many reptiles, including Sonoran desert tortoises ( Gopherus agassizii ), are challenging effectively because they cryptic, occur at low densities, their activity is limited both seasonally daily. We compared efficiency statistical power 2 survey methods appropriate...

Strategies to conserve rare species require identifying resources that function as important habitat elements and promote high demographic performance. Assessing the relative importance of resources, however, can be confounded by natural variation in resource availability hierarchical spatial structure which are organized. Because often vary across environmental gradients, we used gradients together with selection functions variance decomposition assess nest site reproductive performance...

Like all grasslands across North America, the distribution of desert has been reduced markedly, and remnants have altered extensively by humans. In Arizona, New Mexico, Texas, USA, in invaded dozens non-native plants, especially perennial grasses that evolved arid systems with similar climate disturbance regimes. biomass, richness, diversity native plants typically decrease, whereas plant density, litter increase. These changes composition structure community affect animals inhabit grassland...

Vegetation structure and floristic composition strongly influence the of bird communities. To assess vegetation other environmental characteristics on songbirds, we quantified nest-site reproductive success a riparian songbird community in Arizona. Although found interspecific variation associated with nest sites, identified two suites species that chose sites similar characteristics. These "nest groups" were explained largely by height trees. Overall, was low for songbirds this community,...

Mexican spotted owls (Strix occidentalis lucida) occupy narrow canyons on the Colorado Plateau, some of which are subject to high levels recreational activity. These activities represent a potential threat owls, yet due confines canyon walls spatial restrictions would likely eliminate all activity within these canyons. We assessed factors that influenced flush responses (flush or no flush), distances, distances avoidance flights, and behavioral changes in response single hiker approached...

Model selection based on information-theoretic methods (Burnham and Anderson 2002) has gained prevalence as a strategy for analyzing ecological data, especially among wildlife biologists (Stephens et al. 2005). Development of this alternative been refreshing because it encouraged many us to reexamine the analytical strategies we use evaluate models built explicitly biological foundation. However, some proponents now advocate model only reasonable wide range analyses. In particular, there is...

Abstract: Survey techniques that are both reliable and efficient necessary to accurately estimate population parameters, especially for rare species. Cactus ferruginous pygmy‐owls ( Glaucidium brasilianum cactorum; hereafter pygmy‐owls) have declined in southwestern North America surveyed often comply with federal law. We studied owl responses broadcasted calls quantify how detectability response rates (owls/station/transect) vary environmental, spatial, temporal, weather‐related factors....

Dynamics of many amphibian populations are governed by the distribution and availability water. Therefore, understanding hydrological mechanisms that explain spatial temporal variation in occupancy abundance will improve our ability to conserve recover vulnerable amphibians. We used 16 years survey data from intermittent mountain streams Sonoran Desert evaluate how surface water affected survival adult recruitment a threatened amphibian, lowland leopard frog (Lithobates yavapaiensis). Across...