In a companion article (Beier et al. 2006), we identified 2 sets of unreliable inferences that may compromise efforts to conserve the Florida panther (Puma concolor coryi). In spite of serious flaws in methodology and interpretation, these unreliable conclusions have appeared in prominent, peer-refereed scientific journals and have been repeatedly cited and miscited in support of panther conservation. Future editors and referees may reduce these errors by insisting on adherence to an Introduction, Methods, Results, and Discussion (IMRAD) format; checking improbable assertions attributed to earlier papers; and refusing to allow scientific inference in publication formats not subject to scientific peer review (e.g., editorials). We urge conservation biologists to view science as an adaptive process and to use the method of multiple working hypotheses (Chamberlin 1890) that are now a central feature of adaptive resource management (Walters 1986, Williams et al. 2002). We advocate a workshop approach, similar to that used for analysis of data for the northern spotted owl (Strix occidentalis; Anderson et al. 1999), to deal with scientific disagreement where, as in the case with panthers, stakeholders have entrenched points of view. Finally, we recommend the creation of an independent Scientific Steering Committee to address long-term issues of future research and monitoring of Florida panthers.

Presence–absence surveys are a commonly used method for monitoring broad-scale changes in wildlife distributions. However, the lack of power of these surveys for detecting population trends is problematic for their application in wildlife management. Options for improving power include increasing the sampling effort or arbitrarily relaxing the type I error rate. We present an alternative, whereby targeted sampling of particular habitats in the landscape using information from a habitat model increases power. The advantage of this approach is that it does not require a trade-off with either cost or the Pr{type I error} to achieve greater power. We use a demographic model of koala ( Phascolarctos cinereus ) population dynamics and simulations of the monitoring process to estimate the power to detect a trend in occupancy for a range of strategies, thereby demonstrating that targeting particular habitat qualities can improve power substantially. If the objective is to detect a decline in occupancy, the optimal strategy is to sample high-quality habitats. Alternatively, if the objective is to detect an increase in occupancy, the optimal strategy is to sample intermediate-quality habitats. The strategies with the highest power remained the same under a range of parameter assumptions, although observation error had a strong influence on the optimal strategy. Our approach specifically applies to monitoring for detecting long-term trends in occupancy or abundance. This is a common and important monitoring objective for wildlife managers, and we provide guidelines for more effectively achieving it.

Maintenance of sustainable wildlife populations is one of the primary purposes of wildlife management. Thus, it is important to monitor and manage population growth over time. Sensitivity analysis of the long-term (i.e., asymptotic) population growth rate to changes in the vital rates is commonly used in management to identify the vital rates that contribute most to population growth. Yet, dynamics associated with the long-term population growth rate only pertain to the special case when there is a stable age (or stage) distribution of individuals in the population. Frequently, this assumption is necessary because age structure is rarely estimated. However, management actions can greatly affect the age distribution of a population. For initially growing and declining populations, we instituted hypothetical management targeted at halting the growth or decline of the population, and measured the effects of a changing age structure on the population dynamics. When we changed vital rates, the age structure became unstable and population momentum caused populations to grow differently than that predicted by the long-term population growth rate. Interestingly, changes in fertility actually reversed the direction of short-term population growth, leading to long-term population sizes that were actually smaller or larger than that when fertility was changed. Population momentum can significantly affect population dynamics and will be an important factor in the use of population models for management.

Both grand (Oligosoma grande) and Otago skinks (Oligosoma otagense) are threatened with extinction. Predation by introduced mammalian predators, in particular feral cats, is thought to be the major cause of decline. Survival of 5 grand and 2 Otago skink populations was monitored for 3 years before and 3 years during intensive predator control, targeting feral cats but also culling ferrets. In addition, 1 Otago and 2 grand skink populations served as controls. For both species, capture–recapture modeling of skink survival failed to find evidence that survival was significantly influenced by the removal of predators, but retrospective power tests showed uncertainty in this result was high. It is possible the residual predator populations were sufficient to depress skink survival during the treatment interval. Seasonal modulation of apparent survival was evident for both species. Grand skink survival was higher over the winter months and summer survival was characterized by episodic lows, the cause of which remains a mystery. By contrast, Otago skink survival was higher in summer than in winter and did not exhibit the severe lows recorded for grand skinks. My study exemplifies the difficulty in conducting an experiment aimed at guiding management, in a complex predator- species-rich mainland environment.

The source of substrate for initial proliferation and toxigenesis of Clostridium botulinum prior to outbreaks of avian botulism is typically unknown. We investigated factors involved in the initiation of avian botulism outbreaks at Eyebrow Lake, Saskatchewan, Canada, and focused on the role of Franklin's gull ( Larus pipixcan ) mortality as a source of initial substrate for C. botulinum. From 1999 to 2001, hatch-year Franklin's gull carcasses were the predominant source of toxin-laden maggots found prior to outbreaks of avian botulism in waterfowl. Peak carcass density of gulls occurred 1–2 weeks prior to the onset of botulism outbreaks in waterfowl. Nest density at the beginning of the breeding season was a significant predictor of juvenile gull-carcass density. Both the proportion of gull carcasses developing maggots and the proportion of maggot samples containing toxin increased as the season progressed, and carcasses were 22.7 times more likely to develop toxin-laden maggots at mean daily water temperatures ≥20°C than at temperatures <20°C. This was primarily a result of carcasses being 22.2 times more likely to become maggot-laden at temperatures ≥20°C, whereas there was no difference in the occurrence of toxin within maggots developing below or above 20°C. With increasing water temperature, carcasses developed maggots significantly more rapidly and were available for a shorter time period. High density of toxic material from hatch-year Franklin's gull carcasses prior to the onset of botulism coincided with high densities of susceptible birds; hence, gull mortality had the potential to be a major initiating factor for botulism outbreaks at Eyebrow Lake. If management is deemed necessary on lakes enzootic for botulism, intensive surveillance should begin well before the anticipated onset of outbreaks to identify and remove sources of primary substrate. Managers might also consider developing and evaluating strategies to prevent the occurrence of high carcass density, particularly in areas of high nest density of species that may generate high juvenile carcass densities.

Avian cholera is a significant infectious disease affecting waterfowl across North America and occurs worldwide among various avian species. Despite the importance of this disease, little is known about the factors that cause avian cholera outbreaks and what management strategies might be used to reduce disease mortality. Previous studies indicated that wetland water conditions may affect survival and transmission of Pasteurella multocida, the agent that causes avian cholera. These studies hypothesized that water conditions affect the likelihood that avian cholera outbreaks will occur in specific wetlands. To test these predictions, we collected data from avian cholera outbreak and non-outbreak (control) wetlands throughout North America (winter–spring 1995–1996 to 1998–1999) to evaluate whether water conditions were associated with outbreaks. Conditional logistic regression analysis on paired outbreak and non-outbreak wetlands indicated no significant association between water conditions and the risk of avian cholera outbreaks. For wetlands where avian cholera outbreaks occurred, linear regression showed that increased eutrophic nutrient concentrations (Potassium [K], nitrate [NO₃ ], phosphorus [P], and phosphate [PO₃ ]) were positively related to the abundance of P. multocida recovered from water and sediment samples. Wetland protein concentration and an El Niño event were also associated with P. multocida abundance. Our results indicate that wetland water conditions are not strongly associated with the risk of avian cholera outbreaks; however, some variables may play a role in the abundance of P. multocida bacteria and might be important in reducing the severity of avian cholera outbreaks.

Flooded rice fields are important foraging habitats for waterfowl in the lower Mississippi Alluvial Valley (MAV). Waste rice previously was abundant in late autumn (140–492 kg/ha), but early planting and harvest dates in recent years may have increased losses of waste rice during autumn before waterfowl arrive. Research in Mississippi rice fields revealed waste-rice abundance decreased 79–99% during autumns 1995–1996 (Manley et al. 2004). To determine if this trend existed throughout the MAV, we used multistage sampling (MSS) to estimate waste-rice abundance during September–December 2000–2002. Averaged over years, mean abundance of waste rice decreased 71% between harvest (x̄ = 271.0 kg/ha, CV = 13% n = 3 years) and late autumn (x̄ = 78.4 kg/ha, CV = 15% n = 3). Among 15 models formulated to explain variation in rice abundance among fields and across years, the best model indicated abundance of waste rice in late autumn differed between harvester types (i.e., conventional > stripper header) and was positively related to initial waste-rice abundance after harvest. Because abundance of waste rice in late autumn was less than previous estimates in all 3 years, we concluded that waterfowl conservationists have overestimated carrying capacity of rice fields for wintering waterfowl by 52–83% and recommend 325 duck-use days/ha (DUDs) as a revised estimate. We suggest monitoring advances in rice harvest dates to determine when new surveys are warranted and recommend increased management of moist-soil wetlands to compensate for decreased rice abundance.

Aerial infrared videography was used to map spatial distributions of nocturnal sandhill crane (Grus canadensis) flocks and determine crane densities within roosts as an alternative to the currently used diurnal photo-corrected ocular transect method to estimate the size of the mid-continental population. The densities determined from samples taken over the course of a night show variability. Densities measured early in the night (2100 to 2300 hrs) were generally lower than those measured in the time period after midnight and up until cranes prepared to depart their roosts before sunrise. This suggests that cranes may be more active early in the night and possibly still settling into their roosts at this time. For this reason, densities and areas measured later at night and into the early morning were used to estimate population size. Our methods estimated that the annual crane populations along the central Platte River in Nebraska were higher than estimates from the ocular transect method; however both methods showed a similar trend with time. Our population size estimates likely were higher because our methodology provided synoptic imagery of crane roosts along the entire study reach when all cranes had returned to the river, and the nocturnal densities were higher than previous estimates using observations from late evening or early morning. In addition to providing a tool for estimating annual population size, infrared videography can be utilized over time to identify spatial changes in the roosting patterns that may occur as a result of riverine management activities.

We estimated annual local survival rates for after-hatch-year (≥1-yr old) marbled murrelets (Brachyramphus marmoratus) in central California using Cormack-Jolly-Seber mark–recapture models and radiotelemetry, and we modeled the effect of oceanographic conditions, sex, and radiotagging. We captured 331 after-hatch-year murrelets from 1997 to 2003, of which 117 were radiotagged. Recapture rates were best modeled using a term that reflected differences in capture effort among sampling occasions (p_effort) and ranged from 0.068 to 0.166. The most highly ranked model (Φ_{PDO radio}, p_effort) indicated that survival rates were positively related to the strength of the Pacific Decadal Oscillation (PDO) and were negatively affected by radiotransmitters in the year following tagging. Mortality was relatively low in warm-water years, perhaps because murrelets flew inland to breed less frequently and were less exposed to avian predators. Two competing models indicated that survival in the year following tagging was affected by (1) only radiotagging (model Φ_radio, p_effort), and (2) radiotagging and sex (model Φ_{sex radio}, p_effort). Model-averaged survival estimates were 0.868 (SE = 0.074) and 0.896 (SE = 0.067) for males and females, respectively, that were not radiotagged and 0.531 (SE = 0.175) and 0.572 (SE = 0.181) for males and females, respectively, that were radiotagged. Mortality of radiomarked individuals was greatest during a domoic acid (a neurotoxin in the marine environment) bloom in 1998 (Φ = 0.160–0.400) and radiomarking impacts were much less pronounced during typical years (Φ = 0.724–0.810). Additional causes of mortality included predation by peregrine falcons (Falco peregrinus) and oil spills. Survival for nonmarked individuals was similar or higher than what was estimated for murrelets in British Columbia and what was predicted for murrelets based on comparative analyses of other Alcid species, suggesting that mortality of after-hatch-year murrelets is not an immediate threat to population viability in the region.

We studied harvest of Ross's geese in North America by examining recoveries from 30,774 Ross's geese marked from 1989 to 2001 in Queen Maud Gulf Migratory Bird Sanctuary (QMGMBS), Nunavut, in Canada's central arctic. Recoveries reported by hunters in North America provided information about timing and location of harvest for 2,152 birds. Banded Ross's geese were shot and reported mostly from the U.S. (68%) and Canada (30%), but also Mexico (2%) during the study. From 1989 to 2001, there have been eastward shifts in distribution of recoveries from the Pacific Flyway to the midcontinent in the U.S., and from Alberta to Saskatchewan in Canada. Harvest in Canada was concentrated in southern Saskatchewan (85%), whereas U.S. distribution of recoveries was much broader with most recoveries from the Pacific (49%), Central (39%), and Mississippi (12%) Flyways. Continental harvest of Ross's geese began to increase in 1994 concurrent with liberalization of hunting regulations in the Canadian Prairie provinces and the Central and Mississippi Flyways, and the increased propensity of U.S. hunters, who now account for 90% of the continental harvest, to hunt outside of the U.S. Harvest from further liberalization of hunting regulations for light geese as part of the U.S. conservation order has accounted for ≤15% of continental harvest annually since 1998. Nevertheless, increased harvest of Ross's geese from the 1989 hunting season (˜8,000 birds) to the 2001 season (˜90,000 birds) best accounted for annual variation in adult survival, but was unrelated to juvenile survival. Survival of adults was >0.91 before 1994 but declined to ˜0.80 by 1998–2000 hunting seasons. Juvenile survival was relatively stable among years and ranged from 0.33 to 0.41. We found that mortality probability of adults marked with neckbands was 1.94 to 2.62 times higher than for adults without neckbands, but only 1.08 to 1.13 times higher in respective groups of juvenile Ross's geese. Thus, we advise against use of neckbands for estimation of survival in Ross's geese. The similarity and mixing of Ross's geese with snow geese in western and central North America are impediments to separate harvest management of each species. However, geographical adjustment of harvest regulations for Ross's geese in Canada is advised, with the dual objective of reducing midcontinent snow geese while conserving populations of Ross's geese on traditional winter areas in the Pacific Flyway. We recommend Ross's geese continue to be marked with legbands in QMGMBS, their principal breeding range, at least as long as liberal harvest regulations remain in place for reduction of midcontinent snow geese.

Winter flooding of bottomland hardwood (BLH) floodplains in the Mississippi Alluvial Valley (MAV) causes dynamic availability of resources to wintering mallards (Anas platyrhynchos). The effect of changing resource availability on mallard body condition and timing of life-cycle events are important considerations for waterfowl habitat conservation planning in the MAV. During a study of mallards wintering in the Mingo Basin of southeastern Missouri, USA, I collected data on population size, habitat use, behavior, food habits, body composition, and chronology of the prebasic molt during 2 major flood events in 1982. I also analyzed winter (Dec–Feb) hydrological data for 14 rivers in the MAV from 1939–1940 to 1998–1999 to provide a perspective on variation of winter flooding in this ecosystem. Winter floods in the Mingo Basin precipitated ecological events that benefited mallards. During floods, mallards redistributed to shallowly flooded (<50cm) live forest dominated by red oaks (Quercus spp.), increased daily foraging time by up to 8×, consumed 170–222 g dry weight of food/day, increased consumption of animal matter by up to 14×, gained fresh body and lipid mass, and initiated the prebasic molt. Winter flooding of major rivers in the MAV during 1939–1940 to 1998–1999 was highly variable among locations and years. An average of 6.7 ± 2.1 (±SE) and 5.1 ± 1.9 of 17 river gage stations were flooded >5 and >10 days/winter, respectively. Mallards increased daily food consumption by 33–39% over daily existence energy (DEE) levels during floods. These data suggest that previous estimates of foraging carrying capacity in MAV habitats (and other wintering and migration areas where significant fat deposition occurs) using only DEE-based daily food consumption estimates may be overestimated. Consequently, habitat and acre goals set by North American Waterfowl Management Plan Joint Ventures for these areas may be greatly underestimated. The evolutionary adaptations of mallards seem influenced by timing, duration, and extent of winter flooding in the MAV. Efforts to protect the integrity of MAV rivers, associated floodplain habitats, and their winter flow and flooding regimes are critical for sustaining local, regional, and continental mallard populations.

Reliable estimates of breeding-ground demographic rates are needed to develop effective conservation strategies for mallard (Anas platyrhynchos) breeding habitat in eastern North America. We radiomarked 224 female mallards in an agricultural landscape in southern Ontario, Canada, during 1997–2000. At each of 4 sites, 1 during each year, we estimated survival of adult females, breeding incidence, nesting effort, clutch size, nesting habitat use, nest survival, and hen success. We also examined the influence of nest age, date, and habitat on nest survival and the influence of date and female age on survival of adult females. Almost all females remaining on site were observed to initiate ≥1 nest (x̄ = 0.97, range = 0.95–0.98), we detected a mean of 2.07 (1.80–2.36) nests per female each season, and full clutch size averaged 9.56 (9.1–10.0). For most sites, females nested in grassland and hay land more than expected relative to habitat abundance, nested in wetlands and woody habitats in proportion to abundance, and avoided cropland and developed areas. Survival of adult females from 25 March to 15 July averaged 0.75 (0.65–0.84). Estimates from our best model showed relatively uniform survival across the breeding season, with the exception of large decreases for 2 sites during the peak of the onset of hay cutting. Nest survival averaged 0.13 (0.11–0.15). Our best model supported increasing survival with nest age but did not include variation relative to habitat or date, except in hay land. Nest survival in hay land was high relative to other habitats early in the nesting season, but declined sharply with the onset of hay cutting. Hen success averaged 0.37 (0.25–0.46). Because estimated nest survival varied little among sites and habitats and because suitable nesting habitat appeared abundant, we suggest that upland habitat conservation will accrue only limited demographic benefits. Incentives to alter hay-cutting practices may decrease mortality of nests and nesting females, but we believe such incentives are unlikely to be cost efficient and that experiments would be needed to reliably assess benefits.

Population dynamics of mallards (Anas platyrhynchos) in eastern North America likely differ relative to the midcontinent population, but independent management has been hampered by lack of data. We used data from radiomarked females from 4 sites in southern Ontario and 1 site in New Brunswick during 1992–2000 to assess demographic performance during the breeding season and to inform regional management strategies. For each site, we estimated recruitment of female young to 30 days posthatch per breeding female and projected the finite rate of population growth λ, assuming annual survival typical of the region. We constructed a matrix population model for females and conducted perturbation analyses (i.e., analytic sensitivities and elasticities) to predict response of λ to change in vital rates. Excluding 1 site, we estimated mean recruitment of 0.89 (range = 0.79–0.98). At 1 site, duckling survival approaching zero resulted in extremely low estimated recruitment (0.08). Perturbation analyses indicated that λ was highly sensitive to changes in nest survival and nonbreeding survival and moderately sensitive to changes in survival of breeding females. Recruitment for most of our sites was >2 times the mean for the Prairie Pothole Region of Canada and likely was sufficient to maintain populations despite relatively high hunting kill in the region. Despite high sensitivity of λ to nest survival, intensive management to increase nest survival likely would be inefficient because of uniform nest survival among habitats and low nest densities. Because recruitment levels were generally high but densities of breeding pairs low, we recommend protection, enhancement, and restoration of wetlands to maintain and increase habitat suitability for breeding mallards as likely the most cost-efficient management strategy to benefit populations. Relatively high hunting kill and high sensitivity of λ to nonbreeding survival imply that harvest is important to regional population dynamics and suggest the potential effectiveness of adaptive harvest management.

Constructed islands with adequate nesting cover provide secure nesting sites for ducks because islands restrict access by mammalian predators. These islands are costly to construct and should be placed in areas that ensure the greatest use by nesting ducks. We studied mallard (Anas platyrhynchos) and gadwall (A. strepera) nesting on constructed islands in North Dakota in 1996 (n = 20) and 1997 (n = 22) to evaluate factors—particularly amount of perennial grass cover in the surrounding landscape and density of breeding pairs—that possibly influence numbers of initiated nests. We also examined effects of island characteristics, such as island vegetation, on numbers of nests. Numbers of mallard and gadwall nests on islands were negatively related to amounts of perennial grass cover in the surrounding uplands. Numbers of mallard nests were positively related to percentages of tall dense cover on islands. We found no effects of breeding-pair density on numbers of nests initiated by either species, possibly because breeding pairs were abundant on all study sites. Percent shrub cover on islands was a better predictor of island use than was percent tall dense cover. Island use by these species increased with island age and distance from mainland shore. Amounts of perennial cover in landscapes should be primary considerations in determining where to build islands. Our data suggest that use of islands by nesting mallards and gadwalls is greatest in landscapes with little perennial grass cover (i.e., high amounts of cropland). Other researchers documented a positive relation between nest success in upland covers and amount of perennial grass cover in the landscape. Therefore, islands constructed in landscapes with little perennial cover should provide greater gains in duck recruitment rates than islands constructed in landscapes with greater amounts of perennial grass cover.

Ruffed grouse (Bonasa umbellus; hereafter, grouse) populations in the central and southern Appalachians are experiencing declines, which may be linked to deteriorating recruitment. Because nest success is an important component of recruitment, understanding the influence of habitat on nest success is important for developing regional grouse management strategies. Therefore, our objectives were to determine grouse nest success rates, characterize nest site selection, and identify habitat characteristics associated with successful nests in this region. From 1995 to 2002, we located 234 nests, of which 147 (63%) were successful (≥1 egg hatched). We characterized habitat at 167 of these nests and compared successful and unsuccessful nests using logistic regression and Akaike's Information Criterion (AIC). Similarly, we characterized nest site selection by pairing 73 nests with 1–8 nearby systematic sites and conducting a matched-pairs logistic regression followed by AIC. Eleven of 25 candidate models of nest success were supported; distance to a road or opening, ground cover, deciduous canopy cover, coarse woody debris, and basal area were increasingly important predictors of nest success. Increases in basal area, coarse woody debris, and deciduous canopy cover improved the odds of nest success. Alternatively, greater amounts of ground cover and increased distance to a road or opening decreased the odds of a nest being successful. The two supported models of habitat selection were basal area with coarse woody debris and basal area alone. Odds of a habitat being selected increased with both variables. Selection of these habitat elements likely reflects the tendency for females to nest at the base of large trees, stumps, or logs, which can reduce their exposure to predators and seems to improve nest success. Increased ground cover may reduce the female's ability to detect a predator and increase the susceptibility of a nest. We recommend managers ensure coarse woody debris is available for nest sites, particularly when logging operations (e.g., clearcuts, thinnings) remove a high proportion of the standing basal area.

Land area occupied by tallgrass prairie has declined throughout the midcontinental United States during the past 2 centuries, and migratory birds breeding in these habitats have also experienced precipitous population declines. State and federal agencies have responded by restoring and reconstructing grassland habitats. To understand consequences of restoration for grassland bird populations, we combined demographic data collected over 4 breeding seasons (1999–2002) in northern Iowa, USA, with population projection models to estimate population growth rates of 2 declining migratory songbirds, dickcissels (Spiza americana) and bobolinks (Dolichonyx oryzivorus). To determine what parameters were critical for conservation of these species, we estimated relative contributions of nest predation, brood parasitism by brown-headed cowbirds (Molothrus ater), annual survival, and renesting to population growth using elasticity analysis. Based on model simulations, the population growth rate for dickcissels was not high enough to be stable without immigration into the area (λ < 1). For bobolinks, populations could only be stable (λ = 1) if annual survival was relatively high (adult survival >0.7, with juvenile survival between 0.2 and 0.5). Population growth rates were most sensitive to adult survival across a wide range of parameter estimates, whereas sensitivity to brood parasitism and renesting were consistently low. Elasticities associated with nest predation were highly variable and dependent on survival estimates. In the absence of changes in other demographic parameters, eliminating brood parasitism would not be enough to ensure stable populations of either species. Only management focused on increasing adult survival or decreasing nest predation could produce stable populations. Our results underscore the need for reliable adult survival estimates and conservation strategies focused throughout all phases of the annual cycle. In addition, our modeling approach provides an effective framework for investigating the importance of demographic parameters to population growth rates of birds that are influenced by nest predation, brood parasitism, and renesting. Although habitat restoration is one of the few alternatives for conserving communities in threatened landscapes, restoration strategies also need to have positive effects on population dynamics for species of concern, which has not been demonstrated in this grassland system.

Current management recommendations for grassland birds in North America emphasize providing large patches of grassland habitat within landscapes that have few forest or shrubland areas. These Bird Conservation Areas are being proposed under the assumption that large patches of habitat in treeless landscapes will maintain viable populations of grassland birds. This assumption requires that patch size and landscape features affect density and nesting success of grassland birds, and that these effects are consistent among years and regions and across focal species. However, these assumptions have not yet been validated for grassland birds, and the relative importance of local vegetation structure, patch size, and landscape composition on grassland bird populations is not well known. In addition, factors influencing grassland bird nesting success have been investigated mostly in small-scale and short-duration studies. To develop management guidelines for grassland birds, we tested the spatial and temporal repeatability of the influence of patch size and landscape composition on density and nesting success of 3 grassland passerines, after controlling for local-scale vegetation structure, climate, and—when analyzing nest success—bird density. We conducted our study during 4 years (1998–2001) in 44 study plots that were set up in 3 regions of the northern tallgrass prairie in Minnesota and North Dakota, USA. In these study plots we measured density and nesting success of clay-colored sparrows (Spizella pallida), Savannah sparrows (Passerculus sandwichensis), and bobolinks (Dolichonyx oryzivorus). Statistical models indicated that density was influenced by patch size, landscape, region, and local vegetation structure more so than by local vegetation structure alone. Both magnitude and direction of the response of density to patch size varied among regions, years, and species. In contrast, the direction of landscape effects was consistent among regions, years, and between Savannah sparrows and bobolinks. In each species, this landscape effect was independent of patch size. Nesting success was not clearly influenced by patch size or landscape composition, and none of the factors that influenced avian density also influenced nesting success in any of the 3 species. General statements on “optimal habitat” for grassland birds should therefore be viewed cautiously. Instead, long-term studies in different regions as well as a deeper understanding of the local system are needed to determine which factors are most important for grassland birds in a particular area.

Riparian areas are an important part of conservation efforts directed toward minimizing the effects of habitat loss on birds because riparian areas host a large number of bird species. We compared species richness and densities of breeding songbirds among 3 narrow (55–95 m) and 3 wide (400–530 m) forested-riparian areas with adjacent grassland-shrub buffer strips and 3 narrow and 3 wide forested-riparian areas without adjacent grassland-shrub buffer strips, in northeastern Missouri, USA. More bird species occurred in wide than in narrow forested-riparian areas (mean difference = 8.58, 95% CI = 4.82–12.35). Wide forested-riparian areas with and without adjacent buffer strips had similar numbers of species (mean difference = 0.50, 95% CI = −2.77–3.77). Narrow forested-riparian areas with adjacent buffer strips had more species than narrow forested-riparian areas without adjacent buffer strips (mean difference = 9.67, 95% CI = 5.43–13.90). A mixed model with a fixed effect of width had the most support for predicting density of ovenbird (Seiurus aurocapillus), Acadian flycatcher (Empidonax virescens), Kentucky warbler (Oporornis formosus), gray catbird (Dumetella carolinensis), common yellowthroat (Geothlypis trichas), northern cardinal (Cardinalis cardinalis), and indigo bunting (Passerina cyanea). The null model had the most support for wood thrush (Hylocichla mustelina), Louisiana waterthrush (Seiurus motacilla), and field sparrow (Spizella pusilla). Wide forested-riparian areas provided breeding habitat for more bird species than narrow forested-riparian areas, especially forest area–sensitive species. The addition of grassland-shrub buffer strips adjacent to forested-riparian areas increased species richness in those areas and provided habitat for gray catbird, common yellowthroat, northern cardinal, field sparrow, and indigo bunting.

Population numbers of many bird species associated with early-successional or disturbance-dependent habitat types are declining. We used an information–theoretic approach to evaluate hypotheses concerning factors affecting breeding bird densities in different early-successional habitat types. We studied shrubland bird communities in 3- to 5-year-old regenerating forest (n = 3), glade (n = 3), and forest–pasture edge (n = 3) habitat types in the predominantly forested Missouri Ozarks in 1997–1999. We monitored 8 bird species using spot mapping and total mapping techniques, searched for and monitored nests, and measured vegetation structure within nested circular plots. In evaluating breeding densities in these habitat types, we compared support for a global model with year, habitat type, and a habitat type × year interaction to several reduced models and a null model with only an intercept, and we used model-averaged coefficients to evaluate effect size. We found support for the effects of habitat type on breeding densities of prairie warbler (Dendroica discolor) and yellow-breasted chat (Icteria virens); the effects of habitat type and year on densities of blue-winged warbler (Vermivora pinus), eastern towhee (Pipilo erythrophthalmus), and field sparrow (Spizella pusilla); the effect of year on densities of indigo bunting (Passerina cyanea) and northern cardinal (Cardinalis cardinalis); and no effects on densities of white-eyed vireo (Vireo griseus). The effect size of habitat type on breeding densities varied among species and indicated important species-specific differences in habitat use. Most shrubland bird species used both glades and regenerating forests more than forest–pasture edge sites, and breeding densities of some species were higher in regenerating forests than in glades. For some species, patterns in reproductive success (reported as interval nest success) mirrored observed patterns in breeding densities. However, substantial variation existed among species with respect to patterns in habitat use and nest success. Conservation planning for the persistence of birds requiring early-successional habitat types should consider the ephemeral nature of these areas and the potential contribution from young, regenerating forest.

To produce better habitat models, we analyzed a 1977 breeding bird data set with recently developed techniques. Our generalized linear models for specific bird species produced precise descriptions of bird–vegetation relationships, using visually obvious habitat features (e.g., grass, broad-leaved shrubs, and conifers of differing heights). This was, in general, confirmed by canonical correspondence analysis, which related the entire bird community to the vegetation across the successional stages. Nevertheless, our analyses produced some results that contradicted our expectations; ground-nesting species negatively associated with bunch grasses (species that grow in clumps within the Agropyron, Festuca, and Stipa genera), and cavity-nesting species negatively associated with stumps and snags. We speculate that those contrary relationships resulted from nest sites not being a limiting resource. We conclude that visually obvious vegetation features are sufficient to describe most breeding bird–habitat relationships. Further, appropriate landscape management for bird biodiversity requires that all successional stages are present.

Wintering Henslow's sparrow (Ammodramus henslowii) populations rely on lands managed with prescribed burning, but the effects of various burn regimes on their overwinter survival are unknown. We studied wintering Henslow's sparrows in coastal pine savannas at the Mississippi Sandhill Crane National Wildlife Refuge, Jackson County, Mississippi, USA, during January and February 2001 and 2002. We used the known-fate modeling procedure in program MARK to evaluate the effects of burn age (1 or 2 growing seasons elapsed), burn season (growing, dormant), and calendar year on the survival rates of 83 radiomarked Henslow's sparrows. We found strong evidence that Henslow's sparrow survival rates differed by burn age (with higher survival in recently burned sites) and by year (with lower survival rates in 2001 likely because of drought conditions). We found some evidence that survival rates also differed by burn season (with higher survival in growing-season sites), although the effects of burn season were only apparent in recently burned sites. Avian predation was the suspected major cause of mortality (causing 6 of 14 deaths) with 1 confirmed loggerhead shrike (Lanius ludovicianus) depredation. Our results indicated that recently burned savannas provide high-quality wintering habitats and suggested that managers can improve conditions for wintering Henslow's sparrows by burning a large percentage of savannas each year.

We studied use of day roosts by adult, female long-legged myotis (Myotis volans) in 4 watersheds dominated by ponderosa pine (Pinus ponderosa) forest east of the Cascade Crest in Washington and Oregon, USA, 2001–2003. To investigate maternity habitat in managed, xeric forests we radiotracked 87 bats to 195 snag roosts and 34 rock crevices totaling 842 roost-days. Bats changed roosts every 2.7 ± 0.1 (SE) days and averaged 3.6 ± 0.3 roosts per bat. Roosts were 2.0 ± 0.1 km from capture sites, and bats moved 1.4 ± 0.1 km between successive roosts. Six bats (6.9%) day-roosted in rock crevices exclusively, 9 bats (10.3%) used snags and rock crevices, and the remaining bats (82.8%) day-roosted in snags exclusively. Most snag roosts were thick-bark ponderosa pine (n = 103; 52.8%) or thin-bark grand fir (Abies grandis) and white fir (Abies concolor) (n = 74; 37.9%). Over half of all snag roosts (n = 101; 52%) were used by solitary bats; 28 snag roosts (14%) housed >50 bats (large-flyout roosts). Ninety-three percent of large-flyout roosts were in ponderosa pine snags. Large-flyout roosts were larger, taller, and retained more exfoliating bark and total bark than small-flyout roosts (P < 0.05), and small-flyout roosts were larger, taller, and retained more exfoliating bark and total bark than random snags (P < 0.05). Snag roosts were closer to other snags, located in areas of greater snag density, with greater snag basal area and greater basal area of snags >25 cm diameter, and were lower in elevation than random snags (P < 0.05). Pregnant bats divided roost-days almost evenly between thick and thin-bark snags (52.7 vs. 47.3%), whereas lactating bats roosted in thick-bark snags more often than they did in thin-bark snags (80.3 vs. 19.7%, P < 0.0001). Pregnant bats roosted in both upslope and riparian zones (57.5 vs. 42.5%), but lactating bats spent more days roosting upslope than in riparian zones (73.1 vs. 26.9%, P < 0.0001). These findings suggest that reproductive female long-legged bats choose roosts relative to their changing physiological needs. We recommend that management of forests for sustaining habitat of female long-legged myotis in the east Cascades ensure the continued availability of both thick- and thin-bark snags in early stages of decay, in both riparian and upslope positions.

The primary function of military training areas is to support military missions; however, management of natural resources that is compatible with that function has become a focal issue on many military installations. We investigated the relationship between black bear (Ursus americanus) habitat use and weapons-firing exercises at 3 spatial scales on the western portion of U.S. Marine Corps Base Camp Lejeune (Camp Lejeune), North Carolina. In 2000 and 2001, we collected 1,494 telemetry locations for 14 bears (6 males, 8 females). We used spatial contours of human auditory disturbance levels based on the noise generated from firing activities to establish high-, medium-, and low-disturbance noise zones for each firing range. We used the multinomial logit form of discrete choice analysis to examine whether bears exhibited a spatial (i.e., general avoidance of areas associated with military activity) or temporal response (i.e., avoidance of military training areas but only when firing exercises occurred). Except for small areas near the firing positions, differences in bear use among the 3 noise zone areas was mostly a function of the prevalence of selected vegetation types and not a response to military activity. Our temporal analysis further suggested that bears did not respond to weapons exercises; the distance of bears to the nearest high-disturbance noise zone was not associated with the occurrence of weapons exercises.

We studied microhabitat use of the giant panda (Ailuropoda melanoleuca) and the red panda (Ailurus fulgens) from November 2002 to March 2003 at Fengtongzhai Nature Reserve, Baoxing County of Sichuan Province, China, where the 2 species are sympatric. The means of discriminant scores between the 2 species differed, suggesting each had a distinct microhabitat selection pattern, consistent with 1-way ANOVA and Kruskal-Wallis tests. We found that 6 of 19 microhabitat variables differed significantly between these species. Four variables were associated with preferences of the giant panda and 2 from preferences of the red panda. We suggest that environmental factors (slope, fallen log, etc.) other than food availability were primarily responsible for microhabitat separation between the 2 pandas. We hypothesize that the pattern of microhabitat separation did not result from ecological or evolutionary adjustment to reduce interspecific competition but from differences in physiological and ecological requirements. With abundant food resources, slope appeared to be a more important microhabitat feature to the giant panda than any single food factor. The presence of fallen logs and tree stumps was similarly an important microhabitat feature selected by red pandas.

At the request of the U.S. Fish and Wildlife Service (USFWS) and the Florida Fish and Wildlife Conservation Commission (FWC), we provide an independent assessment of the reliability of the scientific literature used to support conservation of Florida panthers (Puma concolor coryi). We independently reached similar conclusions about unreliable scientific inferences before discussing the issues with each other or with others. Although a quarter-century of research supports many published conclusions, 2 sets of unreliable inferences may compromise efforts to conserve the species. The first is a set of 4 unreliable inferences that underlie the Panther Habitat Evaluation Model (PHEM), used by agencies to evaluate projects that may affect panther habitat. Specifically, the following assertions are unreliable: 1) panthers are forest obligates, 2) panthers require large (>500 ha) forest patches, 3) panthers are reluctant to cross 90-m gaps of nonforest habitat, and 4) the value of potential panther habitat declines linearly with distance to a population core in south Florida, USA. These assertions are unreliable because the analyses excluded (without mention or rationale) almost half the available data, compared used habitats to an inappropriate set of available habitats, made inferences about habitat preference without any data on available habitats, were based only on panther locations during daytime, ignored telemetry error, or suffered from other flaws. The second is a set of 2 unreliable inferences about panther demography prior to the genetic restoration effort initiated in 1995. Inferences that neonate survival was ≥0.84 and that the panther population was demographically vigorous prior to 1995 are flawed because the survival analysis ignored mortality during the first 4 months and because other inferences were based on numbers of births and deaths in samples of convenience rather than appropriate vital rates. These faulty inferences about panther demography brought unwarranted credibility to challenges of the genetic restoration program. Faulty inferences of both sets were repeated in subsequent scientific and popular articles; in several instances, previously published work was mis-cited. In its current (2002–2005) version, PHEM is unreliable and should not be used in decisions about panther habitat. Biologists should obtain better demographic estimates and fully analyze how the introgression program has affected these rates.

Increasing reports of human/cougar conflicts may suggest that cougars are increasing in the Pacific Northwest. We determined minimum relative densities and average fecundity, survival, and growth rate of an apparently increasing cougar population in northeastern Washington, USA; northern Idaho, USA; and southern British Columbia, Canada, from 1998 to 2003. Minimum relative densities declined from 1.47 cougars/100 km² to 0.85 cougars/100 km². We estimated average litter size at 2.53 kittens, interbirth interval at 18 months, proportion of reproductively successful females at 75%, and age at first parturition at 18 months for a maternity rate of 1.27 kittens/adult female/yr. Average survival rate for all radiocollared cougars was 59%: 77% for adult females, 33% for adult males, 34% for yearlings, and 57% for kittens. Hunting accounted for 92% of mortalities of radiocollared cougars. The annual stochastic growth rate of this population was λ = 0.80 (95% CI = 0.11). Contrary to accepted belief, our findings suggest that cougars in the Pacific Northwest are currently declining. Increased conflicts between cougars and humans in this area could be the result of the 1) very young age structure of the population caused by heavy hunting, 2) increased human intrusion into cougar habitat, 3) low level of social acceptance of cougars in the area, or 4) habituation of cougars to humans. To help preserve this population, we recommend reduced levels of exploitation, particularly for adult females, continuous monitoring, and collaborative efforts of managers from adjacent states and provinces.

The probability of detecting an animal in a sampled area during a survey consists of 2 components: 1) the probability of an animal being available for detection (availability), which can be highly variable in heterogeneous environments; and 2) the probability of an animal being detected, conditional on its being available for detection (perception). Many surveys only estimate the latter probability because modeling the availability process requires information collected external to the survey. We illustrate estimation of both probabilities in an application to aerial surveys of dugongs (Dugong dugon) in Northern Australian coastal waters where water clarity varies greatly over relatively small spatial scales. Using artificial dugong models and timed depth recorders deployed on 15 wild dugongs to obtain dive profiles, we carried out experiments to determine zones of detectability for dugongs at the range of depths, turbidities, and sea states that spanned the environmental heterogeneity encountered on dugong surveys. Resulting probability estimates were heterogeneous and dependent on the measured conditions. To estimate perception probability, we used a tandem team of 2 observers on either side of the aircraft. This permitted fitting generalized Lincoln–Petersen models with Program MARK. We then used the generalized Horvitz–Thompson estimator, based on the overall detection probability for each individual dugong, to generate population estimates. We also developed a new simulation-based method for estimating standard errors and confidence intervals. We contrast absolute abundance estimates of dugongs in the Torres Strait and Northern Great Barrier Reef regions using both the new and original approaches (Marsh and Sinclair 1989a). For Torres Strait, the new method produced a substantially smaller estimate (11,956 vs. 14,106 dugongs) and a very much smaller standard error (1,189 vs. 2,314 dugongs), whereas the new method produced slightly larger estimates (mean 9,855 vs. 9,193 dugongs, standard error 1,184 vs. 917 dugongs) for the Northern Great Barrier Reef survey.

Wildlife managers require reliable, cost-effective, and accurate methods for conducting population surveys in making wildlife management decisions. Traditional methods such as spotlight counts, drive counts, strip counts (aerial, thermal, infrared) and mark–recapture techniques can be expensive, labor-intensive, or limited to habitats with high visibility. Convenience sampling designs are often used to circumvent these problems, creating the potential for unknown bias in survey results. Infrared-triggered cameras (ITCs) are a rapidly developing technology that may provide a viable alternative to wildlife managers because they can be economically used with alternative sampling designs. We evaluated population-density estimates from unbaited ITCs and road surveys for the endangered Florida Key deer (Odocoileus virginianus clavium) on No Name Key, Florida, USA (461-ha island). Road surveys (n = 253) were conducted along a standardized 4-km route each week at sunrise (n = 90), sunset (n = 93), and nighttime (n = 70) between January 1998 and December 2000 (total deer observed = 4,078). During this same period, 11 ITC stations (1 camera/42 ha) collected 8,625 exposures, of which 5,511 registered deer (64% of photographs). Study results found a difference ( P < 0.001) between methods with road-survey population estimates lower (76 deer) than ITC estimates (166 deer). In comparing the proportion of marked deer between the 2 methods, we observed a higher ( P < 0.001) proportion from road surveys (0.266) than from ITC estimates (0.146). Spatial analysis of deer observations also revealed the sample area coverage to be incongruent between the 2 methods; approximately 79% of all deer observations were on urban roads comprising 63% of the survey route. Lower road-survey estimates are attributed to 1) urban deer behavior resulting in a high proportion of marked deer observations, and 2) inadequate sample area coverage. We suggest that ITC estimates may provide an alternative to road surveys for estimating white-tailed deer densities, and may alleviate sample bias generated by convenience sampling, particularly on small, outer islands where habitat and/or lack of infrastructure (i.e., roads) precludes the use of other methods.

Fertility control is an alternative to lethal removal for managing overabundant populations. This approach invokes several simplifying assumptions; in particular, that specific individuals can be targeted for sterilization. We evaluated the influence of relaxing this assumption on the likelihood of achieving population control by considering potential sources of variation in the capture and sterilization process in an overabundant white-tailed deer (Odocoileus virginianus) population in Cayuga Heights, New York, USA. Using numerical analysis of an individually based seasonal projection model, including demographic stochasticity, we found that heterogeneity in both sampling, and response to trapping, increased the effort required to achieve population reduction within some acceptable degree of certainty. The inability to precisely control the demographic structure of captured deer required increased capture effort to achieve a given reduction. Trap-aversive behavior following capture improved the efficacy of sterilization while trap affinity reduced it. The efficacy of sterilization as a management tool was reduced dramatically by the presence of net immigration and emigration from the population. We found that sterilization could reduce growth rates of overabundant populations under some conditions, but it is unlikely to be a viable means for reducing populations in general, where there is significant net movement of individuals into the population, and where there is imprecise control over the capture process.

We used habitat-selection data from a reintroduced population of elk (Cervus elaphus) in northeastern Nevada, USA, to develop a resource-selection function to adjust nutritional carrying capacity estimates. Constrained estimates provide population levels that minimize overuse of key foraging communities. We estimated economic nutritional carrying capacity (I_NCC) for 236-kg lactating cow elk in autumn 1999 and 2000 to reflect expected animal performance under maintenance (2,550 kcal/kg DM) and good (2,750 kcal/kg DM) levels of standing digestible energy. We used our resource-selection function to redistribute I_NCC densities (RSFD) for aspen (Populus tremuloides), conifer, curl-leaf mountain mahogany (Cercocarpus ledifolius), sagebrush (Artemisia spp.)–herb, and snowbrush ceanothus (Ceanothus velutinus) cover types across the summer range and then adjusted original I_NCC estimates according to these RSFD when expected densities exceeded original I_NCC estimates. Maintenance performance I_NCC estimates were 2,533 cow elk (95% CI: 1,327–3,739) in 1999 and 1,655 (95% CI: 886–2,424) in 2000. Good performance I_NCC estimates were 2,264 cow elk (95% CI: 1,150–3,378) in 1999 and 1,100 (95% CI: 384–1,816) in 2000. The best habitat model provided evidence that forage availability and distance to water influenced habitat selection. Adjustments in I_NCC for 1999 and 2000 and at both performance levels corresponded to decreases of 18–35% in original I_NCC estimates. Decreases were attributed to more cow elk predicted by RSFD to be in aspen, conifer, and sagebrush–herb cover types than predicted by I_NCC. Each year, RSFD predicted that fewer elk would use mahogany and snowbrush cover types than original I_NCC models. The adjusted carrying capacity estimates provided population levels that should avoid appreciable alteration of aspen, conifer, and sagebrush–herb communities while ensuring nutritious resources during lean periods. Our paper provides a critical refinement for nutritional carrying capacity models through incorporating prediction of animal selection of nutritional resources.

Shooting and using poison baits (e.g., strychnine, zinc phosphide) are current management options for controlling Richardson's ground squirrels (Spermophilus richardsonii; RGS). Bullets used for shooting RGS contain lead, fragment upon impact, and RGS carcasses are not usually recovered after being shot. For these reasons, we hypothesized that scavenging birds of prey may be at risk of lead poisoning. To test this, we took radiographs of 15 shot RGS and analyzed the area around the path of the bullet for lead. Lead levels ranged from 0.01 to 17.21 mg/carcass (median = 3.23 mg), and fragments appeared as dust. Two common scavenging hawks (Swainson's and ferruginous hawks [Buteo swainsonii, B. regalis]) consume eviscerated RGS carcasses and would consequently ingest this amount of lead per feeding. In a previous study, an estimated 5.71 mg/kg of lead, eroded in vivo from ingested lead shot, was lethal to bald eagles (Haliaeetus leukocephalus). Fitting the residue values to a normal distribution and based on the mass of an average raptor, we determined that roughly 1 in 5 RGS carcasses had lead levels that exceeded this value. Based on the average amount of lead in carcasses, and assuming that uptake of lead from the carcass is as high as that of eroded lead, we suggest that hawks would have to eat roughly 6.5 carcasses, taking an average of 23 days of feeding on an uninterrupted supply of shot carcasses, to attain a lethal dose of lead. Uncertainties remain, but shot RGS carcasses appear to be an appreciable source of lead that could prove fatal to scavenging hawks. This hazard could be avoided with the collection and disposal of shot carcasses and with the use of (green) ammunition.