HOME RANGE, HABITAT USE, SURVIVAL, AND FECUNDITY OF MEXICAN SPOTTED OWLS IN THE SACRAMENTO MOUNTAINS, NEW MEXICO (original) (raw)
Related papers
The effects of habitat, climate, and Barred Owls on long-term demography of Northern Spotted Owls
The Condor, 2016
Estimates of species' vital rates and an understanding of the factors affecting those parameters over time and space can provide crucial information for management and conservation. We used mark–recapture, reproductive output, and territory occupancy data collected during 1985–2013 to evaluate population processes of Northern Spotted Owls (Strix occidentalis caurina) in 11 study areas in Washington, Oregon, and northern California, USA. We estimated apparent survival, fecundity, recruitment, rate of population change, and local extinction and colonization rates, and investigated relationships between these parameters and the amount of suitable habitat, local and regional variation in meteorological conditions, and competition with Barred Owls (Strix varia). Data were analyzed for each area separately and in a meta-analysis of all areas combined, following a strict protocol for data collection, preparation, and analysis. We used mixed effects linear models for analyses of fecundi...
The Condor, 2005
We used data from Northern Spotted Owl (Strix occidentalis caurina) territories to model the effects of habitat (particularly intermediate-aged forest stand types), climate, and nonhabitat covariates (i.e., age, sex) on owl reproductive rate and apparent survival in southwestern Oregon. Our best model for reproductive rate included an interaction between a cyclic, annual time trend and male breeding experience, with higher reproductive rates in even years compared to odd, particularly for males with previous breeding experience. Reproductive rate was also negatively related to the amount of winter precipitation and positively related to the proportion of old-growth forest near the owl territory center. Apparent survival was not associated with age, sex, climate or any of the intermediate-aged forest types, but was positively associated with the proportion of older forest near the territory center in a pseudothreshold pattern. The quadratic structure of the proportion of nonhabitat farther from the nest or primary roost site was also part of our best survival model. Survival decreased dramatically when the amount of nonhabitat exceeded ϳ50%. Habitat fitness potential estimates (h) for 97 owl territories ranged from 0.29-1.09, with a mean of 0.86 Ϯ 0.02. Owl territories with habitat fitness potentials Ͻ1.0 were generally characterized by Ͻ40%-50% old forest habitat near the territory center. Our results indicate that both apparent survival and reproductive rate are positively associated with older forest types close to the nest or primary roost site. We found no support for either a positive or negative direct effect of intermediate-aged forests on either survival or reproductive rate.
Demography of Mexican spotted owls in the Sacramento Mountains, New Mexico
The Journal of Wildlife Management, 2013
Information on population dynamics is key to gauging the status of threatened or endangered species. We monitored demography of a population of threatened Mexican spotted owls (Strix occidentalis lucida) in the Sacramento Mountains, New Mexico from 2003 to 2011. We estimated reproductive output for territorial pairs of owls; used mark-recapture methodology and Pradel's reparameterized Jolly-Seber models to estimate annual apparent survival rates, recapture rates, recruitment rates, and annual rate of population change (l RJS) for 2005-2009; and used estimates of l RJS to assess short-term population viability. Reproductive output was highly variable for 2004-2011, whereas annual apparent survival and recapture rates were less variable among years. Annual rates of population change exceeded 1.0 for both sexes from 2005 to 2009, and empirical observations of numbers of territorial owls supported the model-based trend estimate. Abundance of territorial owls was strongly related to reproduction within the study area, suggesting that population change was driven largely by internal processes. Population viability analyses suggested that population growth was likely to continue in the short term if current conditions persist. The positive growth rates observed in our study populations are encouraging, and may indicate that current recommendations for recovering this owl are succeeding. However, our estimates of l RJS covered a very short time period, given both the potential lifespan of Mexican spotted owls and the extent of temporal variability in weather typical of the southwestern United States. Longer studies of owl demography than we present will be required to understand long-term population trends, and such studies should extend across the range of the subspecies.
To better understand the habitat relationships of the Mexican spotted owl (Strix occidentalis lucida), and how such relationships might influence forest management, we studied home-range and habitat use of radio-marked owls in ponderosa pine (Pinus ponderosa)-Gambel oak (Quercus gambeli~) forest. Annual home-range size (95% adaptive-kernel estimate) averaged 895 ha * 70 (SE) for 1 2 individuals and 997 ha + 186 (SE) for 7 pairs of owls. On average, the 75% adaptive-kernel contour (a probability contour containing 75% of the owl locations) included 32 and 30% of the annual home range for individuals and pairs, respectively, suggesting high concentration of activity in a relatively small portion ofthe home range. Relative area of three covertypes (ponderosa pine forest, pineaak forest, and meadow) did not differ between seasonal ranges, and owls used these covertypes in proportion to their relative area during both breeding and nonbreeding seasons. In contrast, relative area of four c...
Home range and habitat selection of spotted owls in the central Sierra Nevada
The Journal of Wildlife Management, 2011
We studied home range and habitat selection of radio-marked adult California spotted owls (Strix occidentalis occidentalis) randomly selected from among the breeding population of owls in the central Sierra Nevada, California from June to October 2006. The most parsimonious home-range estimate for our data was 555 ha (SE ¼ 100 ha). Home-range size was positively correlated with the number of vegetation patches in the home range (habitat heterogeneity). We used resource selection ratios to examine selection of vegetation types by owls within our study area. Owl home ranges contained a high proportion of mature conifer forest, relative to its availability, although the confidence interval for this estimate overlapped one. We also used resource selection functions (RSF) to examine owl foraging habitat selection. Relative probability of selection of foraging habitat was correlated with vegetation classes, patch size, and their interaction. Owls showed highest selection rates for large patches (>10 ha) of pole-sized coniferous forest. Our results suggested that spotted owls in the central Sierra Nevada used habitat that contained a high proportion of mature conifer forest at the home-range scale, but at a finer scale (foraging site selection) owls used other vegetation classes interspersed among mature forest patches, consistent with our hypothesis that spotted owls may use other forest types besides old growth and mature forests when foraging. Our study provides an unbiased estimate of habitat use by spotted owls in the central Sierra Nevada. Our results suggest that forest managers continue to protect remaining mature and old-growth forests in the central Sierra Nevada because owl home ranges contain high proportions of these habitats. However, our results also showed that owls used younger stands as foraging habitat so that landscape heterogeneity, with respect to cover types, may be an important consideration for management but we did not attempt to relate our findings to fitness of owls. Thus management for some level of landscape heterogeneity for the benefit of owls should proceed with caution or under an adaptive management framework. ß 2011 The Wildlife Society.
Nesting habitat of Mexican spotted owls in the Sacramento Mountains, New Mexico
The Journal of Wildlife Management, 2013
Understanding the habitat relationships of rare species is critical to conserving populations and habitats of those species. Nesting habitat is suspected to limit distribution of the threatened Mexican spotted owl (Strix occidentalis lucida), and may vary among geographic regions. We studied selection of nesting habitat by Mexican spotted owls within their home ranges in the Sacramento Mountains, New Mexico. We compared characteristics of owl nest trees and nest sites to characteristics of randomly located trees and sites at 2 spatial scales: the general nest vicinity and within activity centers used by spotted owls. Owls nested primarily in mixed-conifer forest (92%), and most nested in cavities in trees or snags (48%), or in dwarf mistletoe (Arceuthobium spp.) witches' brooms (36%). Owl nest trees had greater levels of dwarf mistletoe infection and were larger in diameter than random trees at both of the evaluated spatial scales. Nest trees also were more likely than random trees to be in white fir (Abies concolor) or Douglas-fir (Pseudotsuga menziesii), and in trees or snags with broken tops. Differences between owl nest sites and random sites differed with the scale at which we selected random sites, but at both scales examined, owl nest sites had greater canopy cover and more basal area contributed by large trees and white fir than random sites. In addition, most nest sites occurred in drainage bottoms or on the lower 2 thirds of north-or east-facing slopes. Conservation of owl nesting habitat in this area will require retaining forest patches with high canopy cover and large trees containing cavities or large dwarf mistletoe witches' brooms. Locating forest management treatments on ridgetops or the upper third of slopes and/or on south-or west-facing slopes may reduce impacts to owl nesting habitat while simultaneously targeting the drier forest types most in need of restoration. Ó 2013 The Wildlife Society.
Habitat Selection by Mexican Spotted Owls in Northern Arizona
The Auk, 1994
We compared use of seven habitat types to availability of those types within the home ranges of eight radio-tagged Mexican Spotted Owls (Strix occidentalis lucida). When all habitat types were considered simultaneously, habitat use differed from habitat availability for each owl. Patterns of habitat use varied among individuals and with respect to activity. Owls generally foraged more than or as frequently as expected in virgin mixed-conifer and ponderosa pine (Pinus ponderosa) forests, and less than expected in managed forests. Owls roosted primarily in virgin mixed-conifer forests. We also compared habitat characteristics among foraging, roosting, and randomly available sites. Habitat characteristics differed significantly among plot types. Both roosting and foraging sites had more big logs, higher canopy closure, and greater densities and basal areas of both trees and snags than random sites. Roosting sites had greater canopy closure, more big logs, and greater densities of both trees and snags than foraging sites. Mature forests appear to be important to owls in this region, and different forest types may be used for different activities.
Population Dynamics of Spotted Owls in the Sierra Nevada, California
Wildlife Monographs, 2010
The California spotted owl (Strix occidentalis occidentalis) is the only spotted owl subspecies not listed as threatened or endangered under the United States Endangered Species Act despite petitions to list it as threatened. We conducted a meta-analysis of population data for 4 populations in the southern Cascades and Sierra Nevada, California, USA, from 1990 to 2005 to assist a listing evaluation by the United States Fish and Wildlife Service. Our study areas (from N to S) were on the Lassen National Forest (LAS), Eldorado National Forest (ELD), Sierra National Forest (SIE), and Sequoia and Kings Canyon National Parks (SKC). These study areas represented a broad spectrum of habitat and management conditions in these mountain ranges.