Recovery of threatened and endangered species under the Endangered Species Act (ESA) is accomplished via federally mandated recovery plans. Unfortunately, many recovery plans are limited in effectiveness because they suffer from various limitations; one of which is the lack of scientific data. Because recovery plans for endangered species are inherently plagued by lack of biological data of focal species, new approaches are warranted in recovery-plan development to use what little data are available more effectively. The use of academic–agency partnerships has been suggested as a means to accomplish this objective; academics contribute scientific knowledge, and agency personnel contribute federal regulation expertise. We used the masked bobwhite (Colinus virginianus ridgwayi), the only endangered quail in North America, as a case study to illustrate how such partnerships can be employed to incorporate the latest scientific knowledge into recovery planning. Because the case study of the masked bobwhite embodies many of the difficulties associated with endangered species recovery (e.g., lack of biological data, limited personnel, limited resources), our approach to linking biology, ecology, and management can serve as a general model for recovery planning of other endangered species. We began with a comprehensive review and synthesis of masked bobwhite literature. Based on this information, we then interpreted existing masked bobwhite knowledge within the context of current ecological understanding of quail demography. This integrated knowledge provided the foundation to discuss demographic, habitat, and genetic challenges facing masked bobwhites from the perspective of general population phenomena. Our synthesis led to the conclusions that masked bobwhite populations probably 1) experience chronic low reproduction resulting from living in a desert environment, 2) have not been negatively impacted by the historic conversion of grasslands to brushlands, and 3) have not been as detrimentally impacted as other avian species by the establishment of nonnative grasses within their range because these plants possess functional value for masked bobwhites. We also identified 4 immediate conservation needs: recognition of the significant role México possesses in masked bobwhite conservation and proactive involvement in international collaboration, the need for a reconnaissance of masked bobwhite habitat and populations in México, and the implementation and recognition of the critical role habitat management plays in masked bobwhite recovery efforts. These objectives must be accomplished if recovery is to succeed. Currently, the future of masked bobwhite is precarious. Masked bobwhite recovery inevitably will involve international collaboration as well as partnerships between agency biologists, private landowners, and research scientists.

Scaled quail (Callipepla squamata) populations have been declining since the early 1960s, and there is no clear understanding of what is causing this decline. It has been suggested that reproductive failure is a probable cause of this decline. We used radiotelemetry to evaluate nesting ecology and survival of scaled quail in the Southern High Plains of Texas in 1999 and 2000. We radio-marked 138 hens (66 in 1999 and 72 in 2000) and reported nesting activity on 106 nests. In 1999, 50 nests were detected with a nesting success of 44%. In 2000, 56 nests were detected with a nesting success of 64%. Chick survival was recorded at 21 days posthatch and was analyzed as present or absent, as exact numbers were difficult to determine. Two hens had chicks present at 21 days in 1999, but 16 hens had chicks present at 21 days in 2000. Chick presence with the hen at 21 days was negatively associated with cool and wet weather. Logistic regression revealed predictive relationships for models describing vegetation characteristics at and around nest sites as predictors of nesting success and nest sites. Variables in the models included percentage of bare ground, forb diversity, and amount of visual obstruction at different heights. Hen survival, nesting success, and chick survival were higher in 2000 than in 1999. Differences in vegetation composition and structure were likely responses to differences in precipitation between years. Drought and overgrazing by livestock increase the percentage of bare ground and reduce visual obstruction; these are likely contributors to the reduced scaled quail populations in the Southern High Plains.

Fixed kernel density analysis with least squares cross-validation (LSCVh) choice of the smoothing parameter is currently recommended for home-range estimation. However, LSCVh has several drawbacks, including high variability, a tendency to undersmooth data, and multiple local minima in the LSCVh function. An alternative to LSCVh is likelihood cross-validation (CVh). We used computer simulations to compare estimated home ranges using fixed kernel density with CVh and LSCVh to true underlying distributions. Likelihood cross-validation generally performed better than LSCVh, producing estimates with better fit and less variability, and it was especially beneficial at sample sizes <˜50. Because CVh is based on minimizing the Kullback-Leibler distance and LSCVh the integrated squared error, for each of these measures of discrepancy, we discussed their foundation and general use, statistical properties as they relate to home-range analysis, and the biological or practical interpretation of these statistical properties. We found 2 important problems related to computation of kernel home-range estimates, including multiple minima in the LSCVh and CVh functions and discrepancies among estimates from current home-range software. Choosing an appropriate smoothing parameter is critical when using kernel methods to estimate animal home ranges, and our study provides useful guidelines when making this decision.

There are multiple approaches to sensitivity analysis used to identify the age- (or stage-) specific rate of reproduction or survival that most affects population growth—all of which involve evaluating effects on λ, the dominant eigenvalue of the Leslie matrix. Management recommendations generated by these approaches can be difficult to determine, in part because results are valid only for populations with stable age distributions (i.e., the age structure is constant across years). Although these analytical approaches can identify the quickest way to increase population size to carrying capacity, they cannot identify best management options for short-term goals such as increasing population size above some critical value. We present a perturbation analysis—Vital Rate Sensitivity Analysis (VRSA)—to identify the vital rate that most limits population growth over any specified period by determining which vital rate has the greatest effect on population growth. The VRSA is effective for stable and nonstable age distributions, differentiates optimal short- and long-term management options, can incorporate stochasticity in vital rates, and can differentiate efficacy of alternative management strategies. In addition to being able to compare effects of incremental or specific changes in vital rates, VRSA can be used to compare specific management alternatives that affect single or multiple vital rates. We illustrate use of VRSA for a variety of management alternatives and hypothetical age-structures using demographic data from the literature for greater prairie-chickens (Tympanuchus cupido) and red-cockaded woodpeckers (Picoides borealis). We also present a method, using Monte Carlo simulation, for measuring robustness of VRSA results. Under all of our management scenarios for greater prairie-chickens, we found juvenile survival to be the most sensitive vital rate for the specific comparisons made. For red-cockaded woodpeckers, the most sensitive vital rate differed by management scenario and confidence was higher for larger populations. Results for both species might change given other conditions and/or age structures. The VRSA should be an effective tool for wildlife managers who want to compare alternative management strategies to increase population size. A downloadable Excel spread sheet for calculating VRSA for a life-table is available at  http://ase.tufts.edu/biology/faculty/reed/software.html.

Riparian areas are one of the most complex, diverse, and dynamic environments in forested ecosystems. In areas managed for timber, riparian areas are often protected with unharvested forested buffers, but it is unclear whether these buffers are adequate to maintain the floral and faunal diversity of riparian areas. Amphibians are sensitive to forest management, have high diversity in riparian areas, and are among the most abundant vertebrates in temperate forests; therefore, they are excellent candidates to use in a study of the effects of riparian timber management. We conducted a field experiment with 15 headwater streams in western Maine, USA, randomly assigned to 5 silvicultural treatments. We examined amphibian abundance for 1 year prior to and 2 years following treatment. We also undertook a retrospective study on 12 headwater streams representing 3 treatments where harvests had occurred 4–10 years earlier. We used pitfall traps with drift fences and cover-controlled, active-searches to sample terrestrial and stream amphibians. Wood frogs (Rana sylvatica), eastern red-backed salamanders (Plethodon cinereus), and spotted salamanders (Ambystoma maculatum) were sensitive to timber harvesting along headwater streams. American toads (Bufo americanus) were either unaffected or increased in abundance postharvest. Buffers ranging in width from 11 to 35 m appeared to partially mitigate the effects of timber harvest because abundances were generally higher within the buffer than in the adjacent clearcut for wood frogs, American toads, and to a lesser extent red-backed salamanders. Partial harvests adjacent to headwater streams had the least effect on the riparian amphibian community and should be considered for harvests along headwater streams when managing at the stream scale. Our results show that managers can conduct riparian timber harvesting in a manner that allows a diverse suite of amphibian species to persist in the first years after harvest. It is plausible that these same practices may also mitigate the effects of timber harvesting on other forest species. Long-term effects of riparian timber harvesting on amphibians and other forest species population persistence and viability is a logical next step.

We provide a framework for developing predictive species habitat models using preexisting vegetation, physical, and spatial data in association with animal sampling data. The resulting models are used to evaluate questions relevant to species conservation, in particular, comparing occurrence estimates in reserved and unreserved lands. We used an information–theoretic approach to develop and evaluate a priori models to predict the occurrence of the Del Norte salamander (Plethodon elongatus) within its geographic range on national forests in California. We then evaluated the association of P. elongatus to federal reserved lands using both an empirical and model-based assessment. For the model-based assessment, we calculated the probability of occurrence at existing Forest Inventory and Analysis (FIA) plots that we sampled for salamanders and those that were unsampled within our study area. The Del Norte salamander was more likely to be detected at plots with steeper slopes, older trees, more hardwood basal area, more canopy cover of conifers, more rock, and in areas receiving more precipitation and slightly warmer mean annual temperatures. Only the relationship of percent rock cover to probability of occupancy by P. elongatus was linear. Our best multivariate predictive model explained 66.2% of the deviance, and it correctly classified 96% of the plots at which P. elongatus was detected and 94% of the plots at which it was not. Ten-fold, cross-validation results revealed that the best model was relatively robust with correct classification rates of 87% and 89% for locations at which P. elongatus was detected and not detected, respectively. Our empirical results revealed no strong association with reserved lands. However, when we used our best model to estimate P. elongatus'; probability of occupancy at both sampled and unsampled plots, the mean probability of occupancy within reserved lands was greater than in unreserved lands, suggesting that reserved lands have higher-quality habitat relative to nonreserved lands. Overall, our results indicate that systematically collected forest inventory data can have significant value in developing wildlife habitat models when combined with samples of animal occurrence. Robust, empirically derived habitat models, such as the one we developed, may be useful tools for managers for monitoring the quantity, quality, and distribution of a species' habitat.

Least Bell's vireo (Vireo bellii pusillus) is a federally endangered subspecies of Bell's vireo subject to high levels of brood parasitism by brown-headed cowbirds (Molothrus ater). Brood parasitism greatly reduces the reproductive success of the vireo. We examined the relationship of vegetation structure surrounding nests and of activity near the nest to the incidence of brood parasitism by brown-headed cowbirds of least Bell's vireos. We examined vegetation structure at 3 spatial scales: microhabitat (0–1 m from a nest), mesohabitat (1–11.3 m from a nest), and macrohabitat (greater than 11.3 m from a nest). Nests with high microhabitat cover and mesohabitat cover within 5 m of the nest had a lower incidence of parasitism than those with low cover at these scales. Unparasitized nests had fewer trees greater than 8-cm diameter at breast height (dbh) within 11.3 m, and they had less canopy cover within 5 m than parasitized nests. Cowbirds parasitized nests farther from the edge of the riparian habitat more often than nests near the edge. Activity near the nest did not differ significantly between parasitized and unparasitized nests. We suggest that microhabitat cover is the most important habitat feature influencing the incidence of brood parasitism of least Bell's vireos, and we conclude that cover near the nest reduces the chance that a cowbird will observe nesting activity. We suggest that habitat management for improved breeding success of least Bell's vireos focus on increasing the density of understory vegetation.

The quantity and quality of northern mixed-grass prairie continues to decline because of conversion to agriculture, invasion of woody and exotic plants, and disruption of important ecological processes that shape grasslands. Declines in grassland bird populations in North Dakota, USA, have coincided with these largely anthropogenic alterations to prairie habitat. In grasslands of north-central and northwestern North Dakota, woody plants have increased due primarily to fire suppression, extirpation of bison (Bos bison), and widescale planting of tree shelter belts. In northern grasslands, effects of woody vegetation on survival of grassland birds are poorly understood, and conclusions are based mainly on studies conducted outside the region. We examined nest survival of clay-colored sparrows (Spizella pallida) and vesper sparrows (Pooecetes gramineus) relative to the distance nests were located from aspen (Populus tremuloides) woodland edges and relative to other habitat features near the nest. Clay-colored and vesper sparrow nest survival was higher for nests located near woodland edges, nests with greater cover of Kentucky bluegrass (Poa pratensis), and nests more concealed by vegetation. Vesper sparrow nest survival increased as the percent cover of tall shrubs near the nest increased. Based on video-camera data, the 13-lined ground squirrel (Spermophilus tridecemlineatus) was the most common predator of sparrow eggs and young. Thirteen-lined ground squirrels were more common far from woodland edges than near, and this pattern may, in part, explain clay-colored and vesper sparrow nest survival in relation to woodland edges. In contrast to our results, studies conducted in other grassland systems generally report lower nest survival for grassland birds nesting near trees and shrubs. This disparity in results demonstrates the need to identify specific nest predators and their distributions with respect to important habitat features because these data can be important in explaining—and perhaps predicting—patterns of nest predation.

Reducing fire-induced mortality of cavity trees used by red-cockaded woodpeckers (Picoides borealis) is a challenge and concern in managing this federally endangered species. Prior to the 2001 burning season, 814 active and inactive longleaf pine (Pinus palustris) cavity trees on Eglin Air Force Base (AFB) in northwest Florida, USA, were prepared via 6 protection methods (combinations of mechanical, hand, and backfiring preparation) and monitored for postburn survival after 1 year. We collected data on a suite of variables that may be useful in determining cavity tree predisposition to fire-induced mortality. Mortality of protected trees (2.62%) was significantly lower than that of unprotected trees (6.18%), and protection methods did not differ in their effectiveness at preventing mortality. Bark char was significantly more prevalent on unprepared control trees than protected trees, but no differences were apparent among protection treatments. Mechanical clearing alone took the least amount of time and resources; therefore, we determined mechanical clearing to be the most efficient preparation method. Stem char, needle scorch, percent sap cover, and whether the cavity burned were the characteristics most closely related to mortality 1 year postfire. We recommend that the percent of the bole covered in sap and cavity height be considered when preparing to reduce stem char, needle scorch, and the incidence of burned-out cavities. Managers of red-cockaded woodpecker populations can use these results and recommendations to adjust their burn program, improve the efficiency of their cavity tree protection methods, and better target cavity provisioning for maintaining a viable pool of cavity trees.

Western burrowing owls (Athene cunicularia hypugaea) are endangered in Canada and several western U.S. states. Population declines have been linked with control measures aimed at burrowing mammals and loss of nesting habitat. The owls frequently associate with irrigated agriculture throughout portions of their western U.S. range. To determine potential factors driving the association of burrowing owls with agriculture, we examined availability of suitable nest burrows (burrow availability hypothesis), abundance of potential prey (prey availability hypothesis), and predation of nest burrows (predation hypothesis) for owls nesting in the Snake River Birds of Prey National Conservation Area in southwestern Idaho during 2001–2002. Nest burrow availability did not differ between agricultural and nonagricultural habitats, and occupancy rates of owls in artificial burrows were greater near agriculture. More rodent prey species were live-trapped in agricultural habitat compared with nonagricultural habitat, and there was no difference in relative abundance of prey between habitat types. Pellet remains indicated greater abundance and biomass of prey being consumed in agricultural habitat compared with nonagricultural habitat. Finally, predation rates of dummy nests in agricultural and nonagricultural habitat did not differ. These findings allow us to reject the burrow availability and predation hypotheses, while the prey availability hypothesis remains tenable. Thus, burrowing owls may nest near irrigated agriculture in southwestern Idaho because of increased diversity or availability of prey. We suggest that research is needed to determine how widespread this prey availability relationship may be and how management of burrowing owls in agricultural landscapes may take advantage of this apparent rich prey resource.

The conservation of golden eagles (Aquila chrysaetos) requires a thorough understanding of their demographic parameters. Productivity, commonly measured as the number of nestlings or fledglings per pair, is the parameter reported by most studies of nesting golden eagles and is often used as a measure of their population status. Survival may be an equally or more important parameter to measure; however, survival rates of golden eagles are not well documented. We used satellite telemetry to estimate the probability of first-year survival for migratory golden eagles raised in Denali National Park and Preserve, Alaska, USA. We calculated the probability of first-year survival using program MARK. Based on the best approximating model, monthly survival probability was 0.88 ± 0.04 (mean ± SE) during the autumn migration and early winter period for golden eagles marked in 1997 and 0.78 ± 0.05 during the same period for golden eagles marked in 1999. Monthly survival during the remaining 3 periods (i.e., late winter, spring migration, summer) was 0.94 ± 0.03 for both cohorts. Survival during the entire 11-month period was 0.34 ± 0.10 for the 1997 cohort and 0.19 ± 0.07 for the 1999 cohort. Causes of mortality included starvation, electrocution, and poaching. Our results indicate that low first-year survival may limit recruitment and we recommend that golden eagle monitoring programs include survival estimates.

The tassel-eared squirrel (Sciurus aberti) is often used as an indicator species in southwestern ponderosa pine (Pinus ponderosa) forests. Because of more than a century of fire suppression, grazing, and timber harvest, these forests have become increasingly prone to catastrophic wildfire, resulting in pressure to implement large-scale treatments to reduce fire threat and restore ecosystem function. However, such treatments could have dramatic effects on tassel-eared squirrels and other wildlife. Because of emerging plans for thinning southwestern forests to reduce fire threat, we undertook a modeling effort to produce spatial data to examine the results of proposed management actions on squirrel habitat. We used squirrel density and recruitment data from 9 study areas located in the Flagstaff region of northern Arizona, USA, linked with spatial data on forest structure developed from remote-sensing imagery. We used a multiscale approach to analyze relationships between forest structure and squirrel density and recruitment. We then used an information-theoretic approach to identify the most parsimonious models for both squirrel density and recruitment. The most strongly supported models of squirrel density included local-scale basal area and >60% canopy cover at the 65-ha spatial scale. For squirrel recruitment, 4 different models that included both local-scale basal area (m²/ha) and variations of canopy cover over extents of approximately 160–305 ha were strongly supported. Using the most parsimonious models, we created spatial data layers representing both squirrel density and recruitment across an 800,000-ha landscape in northern Arizona. Our approach resulted in spatially explicit models that can be used in efforts to predict the effects of forest management on squirrel populations.

We evaluated interspecific habitat use within a salt marsh small mammal assemblage on Mare Island, Solano County, California, USA, from 1989 to 1992, with emphasis on the endangered salt marsh harvest mice (Reithrodontomys raviventris). We livetrapped small mammals during 125 trap sessions at 20 different areas throughout Mare Island for a total of 55,189 trap-nights. We captured the salt marsh harvest mouse 4,147 times; the house mouse (Mus musculus), 1,936 times; the California vole (Microtus californicus), 372 times; and the shrew (Sorex spp.), 117 times, among 12,927 captures. We captured fewer than 10 rats (Rattus spp.), and we did not capture any western harvest mice (Reithrodontomys megalotis) or deer mice (Peromyscus maniculatus). We sampled vegetation characteristics at each trap location during 79 of 125 trap sessions for a total of 5,523 trap locations. During the summer, breeding, and fall seasons, habitats characterized by increased cover of forbs, particularly fat hen (Atriplex patula), were used to a greater extent by male than female salt marsh harvest mice. Both sexes of salt marsh harvest mice used areas with less cover of forbs, particularly fat hen and pickleweed (Salicornia virginica), during the winter, spring, postbreeding, and prebreeding seasons. House mice used habitats that were more patchily distributed or fragmented than salt marsh harvest mice. Habitat characteristics that were positively associated with salt marsh harvest mice tended to be negatively associated with house mice. Voles used habitats characterized by positive associations with shrub, pickleweed, litter, and woody debris cover, foliage height densities (0 to >40 cm), and mean vegetation height. Vole habitat use was negatively associated with water cover and depth. We suggest that reducing habitat patchiness throughout tidal marshes may reduce salt marsh harvest mouse competition with house mice, and restoring tidal action may reduce habitat competition with voles.

Understanding white-tailed deer (Odocoileus virginianus) fawn survival is critical for managing herd dynamics and setting effective harvest regulations. We fitted white-tailed deer fawns with radiocollars during spring 2001 (n = 35) and 2002 (n = 40) to quantify cause-specific mortality, survival, and home-range size and composition in the southwestern Lower Peninsula of Michigan, USA. We monitored fawns a minimum of twice a week until they died, were censored, or the tracking period ended. Seventeen of 75 fawns died. The primary causes of mortality were legal hunting (n = 5) and deer–vehicle collisions (n = 5). Other causes included dehydration, bacterial infection, suspected coyote (Canis latrans) predation, drowning, and malnutrition. Survival probabilities for 2001 and 2002 radiocollared fawns to 30 days postcapture were 0.97 and 0.93, respectively. Capture-to-prehunt (127 days) fawn-survival probabilities were 0.91 for 2001 fawns and 0.90 for 2002 fawns. Posthunt (220 days) fawn survival probabilities were 0.76 for 2001 fawns and 0.85 for 2002 fawns. Annual estimated fawn-survival probabilities were 0.76 for 2001 and 0.75 for 2002. Mean annual home-range size for fawns was 75.36 ha. Habitat quality and land cover and use were potential factors that contributed to our high fawn survival. Our results can aid wildlife biologists in developing, refining, and validating deer population models as well as devising and balancing white-tailed deer population management decisions in an agroforested landscape.

A major objective of the 1995 Florida Panther (Puma concolor coryi) Recovery Plan is the establishment of 2 additional panther populations within the historic range. Our goal was to identify prospective sites for Florida panther reintroduction within the historic range based on quantitative landscape assessments. First, we delineated 86 panther home ranges using telemetry data collected from 1981 to 2001 in south Florida to develop a Mahalanobis distance (D²) habitat model, using 4 anthropogenic variables and 3 landscape variables mapped at a 500-m resolution. From that analysis, we identified 9 potential reintroduction sites of sufficient size to support a panther population. We then developed a similar D² model at a higher spatial resolution to quantify the area of favorable panther habitat at each site. To address potential for the population to expand, we calculated the amount of favorable habitat adjacent to each prospective reintroduction site within a range of dispersal distances of female panthers. We then added those totals to the contiguous patches to estimate the total amount of effective panther habitat at each site. Finally, we developed an expert-assisted model to rank and incorporate potentially important habitat variables that were not appropriate for our empirical analysis (e.g., area of public lands, livestock density). Anthropogenic factors heavily influenced both the landscape and the expert-assisted models. Of the 9 areas we identified, the Okefenokee National Wildlife Refuge, Ozark National Forest, and Felsenthal National Wildlife Refuge regions had the highest combination of effective habitat area and expert opinion scores. Sensitivity analyses indicated that variability among key model parameters did not affect the high ranking of those sites. Those sites should be considered as starting points for the field evaluation of potential reintroduction sites.

We used more than 10 years of data on buffalo herds in a Geographic Information System (GIS) of Klaserie Private Nature Reserve (KPNR) to examine ranging behavior and habitat selection at multiple temporal and geographic scales. We compared 3 methods of empirical home range estimation: minimum convex polygons (MCP); a fixed-kernel method; and a new local nearest-neighbor convex-hull construction method (LoCoH). For 3 herds over 5 years (1995–2000), the southern herd (SH) had the largest range, the focal study herd (FH) had the intermediate range, and the northern herd (NH) had the smallest range. The LoCoH method best-described the ranges because it accommodated user knowledge of known physical barriers, such as fences, whereas the MCP and kernel methods overestimated ranges. Short-term ranges of the FH over 9 years reveal that buffalo travel farther and range wider in the dry season than the wet. Habitat selection analyses on broad vegetation categories showed preference for Acacia shrub veld and Combretum-dominated woodlands. We found no significant selection of habitat at a fine geographic and temporal interval using the remotely sensed normalized difference vegetation index (NDVI), but the index was correlated to ranging behavior at a larger geographic scale. We found that buffalo selected areas within 1 km of water sources, and an isopleth analysis using the new LoCoH method showed preference for riverine areas in both seasons. This suggests that buffalo preferentially select for areas near water, but they may range farther in the dry season for higher-quality food. As KPNR has a higher density of water than the neighboring Kruger National Park (KNP), this study provides a comparison of buffalo response to water availability in a smaller reserve and important information to managing the buffalo population as part of the larger Greater Kruger Management Area (GKMA).

The continental population of northern pintails (Anas acuta; hereafter pintails) has declined since the late 1970s, possibly due to poor breeding propensity, low nest success, and low survival rates in response to habitat loss. Survival estimates are unavailable for several winter and migration areas including the Playa Lakes Region (PLR) of northwestern Texas, USA. We investigated winter survival rates, documented periods of mortality, and identified possible causes of mortality for 159 and 168 radiotagged female pintails during 23 October 2002–18 February 2003 and 10 October 2003–18 February 2004, respectively. We located all radiotagged pintails at least once weekly to verify survival status and used-known fate modeling in program MARK to test the influence of capture period, female age class, body mass, and capture location on survival rates. Cumulative survival for the 119-day period in 2002–2003 was 0.925 (95% CI = 86.0–96.3). During 2003–2004, for a 134-day period, survival estimates declined to 0.694 (95% CI = 57.1–79.5). The period of highest mortality occurred during the pintail hunting season with 88% of deaths during 2002–2003 and 34% of deaths during 2003–2004 occurring during this period. Age class and capture period did not affect survival rates either year. There was a positive linear correlation between body mass at time of capture and survival rates during winter for 2003–2004. The lower survival during 2003–2004 was probably due to fewer wetlands being available in the PLR. Our results suggest that habitat conditions and hunting disturbance impact survival of pintails in the PLR of Texas. To maintain or increase wintering pintail survival in the PLR, management should expand wetland availability to wintering waterfowl, enhance food resources, provide refuging areas, and initiate a means for perpetual conservation of playas.

Waterfowl management on breeding grounds focuses on improving nest success, but few studies have compared waterfowl nest success and factors affecting nest survival along a wetland gradient and simultaneously identified nest predators. We monitored nests (n = 195) of common pochards (Aythya ferina) in Trebon Basin Biosphere Reserve, Czech Republic, during 1999–2002. Daily nest survival rates (DSRs, logistic-exposure) declined from island (0.985, 95% confidence interval, 0.978–0.991) to overwater (0.962, 0.950–0.971) and terrestrial (0.844, 0.759–0.904) nests. The most parsimonious model for DSRs included habitat class (DSRs: island > overwater > terrestrial) and nest visibility. Nest survival was improved by reduced nest visibility, increased water depth, and increased distance from the nest to habitat edge in littoral habitats. On islands, nest success increased with advancing date and increased distance to open water. A model of constant nest survival best explained the data for terrestrial nests. There were no observer effects on DSRs in any habitat. In 2003, artificial nests (n = 180; 120 contained a wax-filled egg) were deployed on study plots. The model that best explained variation in DSRs for artificial nests included only 1 variable: habitat class (DSRs: island ≥ overwater > terrestrial). Mammalian predation of artificial nests (by foxes [Vulpes vulpes] and martens [Martes spp.]) was more likely in terrestrial habitats than in littoral habitats or on islands. By contrast, corvids and marsh harriers (Circus aeruginosus) prevailed among predators of overwater and island nests. Our data indicate that artificial islands and wide strips of littoral vegetation may represent secure breeding habitats for waterfowl because those habitats allow nests to be placed in areas that are not accessible to, or that are avoided by, mammalian predators. Management actions should be aimed at preserving these habitats. This, along with creation of new artificial islands, could help to enhance breeding productivity of pochards and possibly other waterfowl species inhabiting man-made ponds.

Duckling survival is an important component of waterfowl population dynamics, and we provide the first-known estimates of duckling survival for common goldeneyes (Bucephala clangula) at the northern limit of their range in Interior Alaska. We color-marked common goldeneye ducklings from 91 broods and radio-marked a subset of the females (n = 39) from a nest-box population in the boreal forest during the summers of 2002 and 2003. We monitored 46 broods in 2002 and 2003 combined and estimated daily survival rates (DSR) and survival to 30 days of age using program MARK. We modeled DSR in relation to year, linear trend across season, duckling age, female age, female body condition, initial brood size, and daily precipitation. Model-averaged duckling survival estimates from the mean yearly hatch date to 30 days of age were 0.64 (95% CI, 0.37–0.90) and 0.67 (95% CI, 0.54–0.80) for 2002 and 2003, respectively. Our best-approximating model indicated that survival differed by year and increased in a linear manner over the course of the 2002 season. Precipitation had a consistent negative effect on duckling survival in both years across models, whereas duckling age did not explain much of the variation in daily survival rates. In light of the decline of many populations of sea ducks, we suggest that more effort should be expended to obtain estimates of other population parameters for common goldeneyes, and monitoring programs should attempt to estimate populations more precisely to identify population-level changes in the future.

Spinning-wing decoys are strong attractants to ducks and increase kill rates over traditional decoying methods. However, it is unknown whether all duck species are attracted similarly to spinning-wing decoys and whether the effectiveness of these decoys changes with latitude. We examined the effectiveness of spinning-wing decoys for 9 species of dabbling ducks during 545 experimental hunts in California (1999–2000), Minnesota (2002), Manitoba (2001–2002), Nebraska (2000–2002), Missouri (2000–2001), and Arkansas (2001–2003). During each experimental hunt, we systematically alternated between 2 paired decoy treatments every 15–30 min (depending on study site): traditional decoys only and traditional decoys with a spinning-wing decoy. Overall, 70.2% (n = 1,925) of dabbling ducks were harvested (shot and retrieved) when spinning-wing decoys were turned on, ranging from 63.6% (n = 187) in Missouri to 76.4% (n = 356) in Minnesota. Effectiveness of spinning-wing decoys increased with latitude of study sites. Proportions of ducks shot when spinning-wing decoys were turned on differed among species, from a low of 50.0% (n = 8) for cinnamon teal (Anas cyanoptera) to a high of 79.0% (n = 119) for American wigeon (A. americana). The probability of being shot when spinning-wing decoys were turned on increased with annual survival rates among species; for example, spinning-wing decoys were more effective for American wigeon and mallard (A. platyrhynchos) than they were for cinnamon teal and American green-winged teal (A. crecca). Effectiveness of spinning-wing decoys did not differ consistently by age or sex of harvested ducks. Our results indicate that the effectiveness of spinning-wing decoys differs among duck species and changes with latitude; thus, consideration of these effects may be warranted when setting harvest regulations and methods of take.

Despite greater harvest rates of males, mallard (Anas platyrhynchos) populations exhibit male-biased sex ratios, presumably because females experience greater mortality during breeding seasons than do males. Nest success and adult female survival during the breeding season greatly impact mallard population growth; however, no study has evaluated breeding-season survival of males and females simultaneously using radiotelemetry. We captured, radiomarked, and monitored 90 male and 272 female mallards during 2 breeding seasons in the Prairie-Parkland region of Canada (Manitoba 1998, Saskatchewan 1999). Model-averaged estimates of female breeding season (i.e., 15 Apr–14 Jul) survival probabilities were 0.84 (SE = 0.031) in 1998 and 0.71 (SE = 0.040) in 1999. Estimated survival probabilities of paired males were 0.99 (SE = 0.016) in 1998 and 0.98 (SE = 0.025) in 1999; survival estimates for unpaired males were 0.92 (SE = 0.052) in 1998 and 0.85 (SE = 0.083) in 1999. Female mortality was greatest during periods of intensive nesting, whereas limited male mortalities precluded identification of attributes linked to mortality. Our results suggest that breeding-season survival of males has little impact on mallard population growth, and that management efforts to increase female survival rates offer greater potential to enhance mallard production.

Abdominally implanted radiotransmitters with percutaneous antennas are increasingly used to monitor movements, survival, and reproduction of waterbirds. However, there has been relatively little assessment of the effects of such radios on avian demographic parameters or migration. We implanted either a 26- or 35-g abdominal transmitter with percutaneous antenna in 198 adult female lesser Canada geese (Branta canadensis parvipes) in Anchorage, Alaska during 2000 and 2001. We compared migration chronology, reproductive effort, and survival of radiomarked females to 118 control females marked with leg bands. Arrival dates following spring migration were similar among females in different treatments in 2001. However, in 2002, wind direction during late migration was less favorable, and arrival of females with 35-g radiotransmitters lagged 1–2 days behind that of control females. Nest initiation dates, clutch size, and mean egg volume were similar for 152 nests of females that lacked radios and 62 nests of radiomarked females. Estimated nesting propensity for females with operable radiotransmitters was 61% and 72% in 2001 and 2002, respectively. Apparent annual survival (φ = 0.82, 95% confidence interval: 0.76 to 0.87) was similar among treatments in the first year after geese were marked. In the second and third years after marking, model-averaged estimates for survival of females with large radiotransmitters were 10% lower than estimates for control females. However, the effect of large radios on long-term survival was equivocal because of uncertainty surrounding treatment estimates. We conclude that abdominally implanted radiotransmitters with percutaneous antennas had small effects on migration chronology but no apparent effects on fecundity. Abdominal transmitters can provide unbiased estimates of anserine survival in the first year after deployment. Because of the potentially greater effects of larger transmitters on migration and long-term survival, we recommend that biologists minimize the size of implanted transmitters and deploy radios with caution if long-term survival of marked birds is a concern.

Habitat management for ducks has significant implications for the conservation of other species. We hypothesized that, because of their flagship and umbrella characteristics, upland-nesting ducks might be effective surrogate species for songbird and shorebird conservation in the dry mixed-grass prairie. We tested this by comparing effects of habitat management (cattle grazing deferments and field size), distance to other habitat (water, cropland/forage, roads), and vegetation, on the richness and density of ducks, songbirds, and shorebirds in southern Alberta, Canada. There were no consistently similar responses to these habitat characteristics among ducks, songbirds and shorebirds. Despite their conceptual appeal, ducks are, therefore, unlikely to be good surrogate species for avian conservation in the dry mixed-grass prairie. Habitat managers and conservation planners should empirically validate whether habitat management for ducks positively affects other species, if this is a management objective. Our results suggest that in dry mixed-grass prairie, deferring cattle grazing is likely to increase densities of only lesser scaup but that grazing, in general, can be used by managers to create a heterogeneous habitat that supports many species.

Wood duck (Aix sponsa) hens are known to lay eggs in nests of other wood ducks. Low levels of intraspecific nest parasitism can increase the number of ducklings produced, but at high levels, increased numbers of eggs are offset by reduced hatching success and elevated nest abandonment. Such effects have been observed in nest boxes, stimulating interest in the role of intraspecific nest parasitism in natural cavities. We found high rates of nest parasitism (85% of nests) in natural cavities by applying microsatellite genetic markers to examine maternity for clutches laid in floodplain and upland forests. Clutch sizes, number of parasites per nest, and the number of parasitic eggs deposited per nest were greater in tree cavities located in floodplain than in upland forests (35.2%, 63.6%, 75.0% greater, respectively; P < 0.05), although the proportions of nests parasitized were similar (100% of floodplain nests versus 80% of upland nests, P = 0.11). We compared our data to almost 40 years of published data from studies of wood ducks using artificial nest boxes. Clutch sizes in natural cavities were smaller than reported for 3 populations using nest boxes (10.3%, 29.4%, and 49.2% smaller; P < 0.05), except when only floodplain nests were considered (5.0% larger, 11.6% and 28.8% smaller, P > 0.05). Fewer parasites (1.5 ± 0.1 parasites) contributed to nests in tree cavities than in 1 box-nesting population (2.7 ± 0.04, P < 0.05). We suggest that the high parasitism rates observed in natural cavities reflect the accuracy of microsatellite techniques relative to other methods and that conspecific nest parasitism is pervasive among wood ducks, even in natural tree cavities that are more widely dispersed and well hidden than nest boxes. However, despite the large proportion of cavity nests parasitized during this study, parasitism did not severely depress breeding productivity, as observed in some box-nesting populations. Long-term and experimental research on factors contributing to extremely large clutches in nest boxes could improve the efficacy of nest-box programs.