Forest bats of eastern North America select habitats for roosting, foraging, and winter hibernation/migration over a myriad of scales. An understanding of forest-bat habitat use over scales of time and space is important for their conservation and management. The papers in this Special Section report studies of bat habitat use across multiple scales from locations across the eastern forests of North America. The consensus of the studies in the Special Section is that the larger portion of the variability in bat habitat use occurs at the smaller scales of sites (roost trees) and stands (foraging areas). Nevertheless, it was also recognized that these features occur discontinuously across larger-scale watersheds and landscapes.

To understand bat biology and appreciate their dependence on and role within forested ecosystems, the biological resolution at which studies are directed must elucidate species and gender patterns. We studied species- and gender-specific aspects of summer range extent and stand selection in northern long-eared bats (Myotis septentrionalis) and little brown bats (M. lucifugus) in the Greater Fundy Ecosystem, New Brunswick, Canada, using trapping, radiotelemetry, and ultrasonic monitoring. Our results suggested that this 2-species system is comprised of 4 ecologically distinct groups with respect to site selection and range extent for roosting and foraging. All bats exhibited an affinity to specific roosting areas. Myotis septentrionalis roosted and foraged in the forest interior. The roosting and foraging areas for females were 6.1 times and 3.4 times larger, respectively, than for males. Both genders foraged in site types in proportion to their availability. Myotis lucifugus females roosted in buildings outside the core study area, and those captured in the forested landscape were transients. Compared to male and female M. septentrionalis, male M. lucifugus had intermediate-sized roosting areas but the largest foraging areas. Water sites were selected during foraging more than expected. Bat foraging activity, measured acoustically at 8 site types, was greatest at lakes and least above the forest canopy. Male M. lucifugus activity levels were positively associated with temperature and the amount of mature coniferous forest and water within 1 km of the sampling site, and they were negatively associated with the amount of mature deciduous forest within 1 km of the site. Our results suggested that understanding gender effects is crucial for accurate characterization of forest bat habitats. Studies of bats that combine data for genders, species, or guilds may produce spurious results and may be of minimal value for, or actually hinder, bat conservation and management programs.

The endangered Indiana bat (Myotis sodalis) requires very specific habitats to provide necessary day-roosting and foraging resources during the spring and summer months throughout its distribution in the eastern United States. Maternity colonies of Indiana bats are almost always found under the exfoliating bark of dead or dying trees. Furthermore, they switch frequently among multiple roosts within large but still somewhat local areas. Therefore, habitats with large numbers of snags or decadent trees are needed to support Indiana bat maternity colonies. These habitats arise naturally and anthropogenically in a variety of ways. However, these conditions often are rare relative to other forest conditions. In the Midwest, such as southern and central Illinois, USA, maternity colonies are more commonly associated with bottomland, riparian, wetland, or other hydric forest types. It is unclear if this occurs because areas with large numbers of snags are more common in these habitats, if maternity colonies prefer these habitats for their foraging resources, or if decades of intensive agriculture have restricted colonies to these habitats. Because many large maternity colonies have been observed in hydric habitats of the Midwest, I hypothesize that these are preferred maternity habitats. Moreover, very few large maternity colonies have been located using upland forest habitats within the region. Elsewhere, such as in the central and southern Appalachians, maternity colonies have been located in upland areas where bottomland habitats are less extensive. However, these colonies are usually characterized by small numbers of bats and ephemeral persistence. Future conservation efforts for the Indiana bat should focus on protecting and regenerating bottomland habitats along the major river systems of the midwestern United States. It is within these bottomland and riparian habitats that future large and long-term maternity colonies will be established.

Bats likely incorporate multi-scale criteria when selecting roost sites, which may change across different landscapes. During summers 2002 and 2003, we used radiotelemetry to investigate day-roost selection of evening bats (Nycticeius humeralis) at multiple scales in mature longleaf (Pinus palustris; natural) and intensively managed loblolly pine (P. taeda; managed) landscapes in the Gulf Coastal Plain of Georgia, USA. We used Akaike's Information Criterion (AIC) to evaluate models describing roost-site selection at the tree, plot, stand, and landscape scales. Evening bats on the natural site selected day-roosts based on tree, plot, and landscape characteristics, but bats on the managed site selected day-roosts only at the tree and plot scale. We hypothesize that greater availability of roosting structures (i.e., abundant large trees and snags) throughout the natural site allowed evening bats to select day-roosts that had favorable landscape characteristics (i.e., closer to water and foraging sites), possibly providing benefits from reduced commuting costs. On the managed site, the relatively young age structure of stands resulted in less-abundant roosting structures throughout the landscape, resulting in selection only at the tree and plot scales. Evening bats appeared to select day-roosts that provide energetic benefits when landscape conditions permitted, however, replicated studies are needed to examine the relationship between energetics and roost availability. Land management on pine landscapes of the southeastern United States that promotes large trees, retention of snags, and an open midstory appears to provide abundant roost structures for evening bats. On managed landscapes, roost sites for evening bats may be provided by retention of forked-topped pines in managed stands and by allowing maturation and senescence of trees in set-aside areas, such as streamside management zones, to promote snag and cavity formation.

During 2001, we used active acoustical sampling (Anabat II) to survey foraging habitat relationships of bats on the Savannah River Site (SRS) in the upper Coastal Plain of South Carolina. Using an a priori information-theoretic approach, we conducted logistic regression analysis to examine presence of individual bat species relative to a suite of microhabitat, stand, and landscape-level features such as forest structural metrics, forest type, proximity to riparian zones and Carolina bay wetlands, insect abundance, and weather. There was considerable empirical support to suggest that the majority of the activity of bats across most of the 6 species occurred at smaller, stand-level habitat scales that combine measures of habitat clutter (e.g., declining forest canopy cover and basal area), proximity to riparian zones, and insect abundance. Accordingly, we hypothesized that most foraging habitat relationships were more local than landscape across this relatively large area for generalist species of bats. The southeastern myotis (Myotis austroriparius) was the partial exception, as its presence was linked to proximity of Carolina bays (best-approximating model) and bottomland hardwood communities (other models with empirical support). Efforts at SRS to promote open longleaf pine (Pinus palustris) and loblolly pine (P. taeda) savanna conditions and to actively restore degraded Carolina bay wetlands will be beneficial to bats. Accordingly, our results should provide managers better insight for crafting guidelines for bat habitat conservation that could be linked to widely accepted land management and environmental restoration practices for the region.

Knowledge and understanding of bat habitat associations and the responses of bats to forest management are critical for effective bat conservation and management. Few studies have been conducted on bat habitat use in the southeast, despite the high number of endangered and sensitive species in the region. Our objective was to identify important local, stand, and landscape factors influencing bat habitat use in northwestern South Carolina, USA. We hypothesized that use would be greatest 1) at points with relatively sparse vegetation, 2) in early successional and mature stands, and 3) at points close to streams. We also predicted that species would exhibit different patterns of habitat use based on morphology. We placed Anabat II bat detectors at points located in 3 forest types and 3 age classes to record bats from May–August 2004 and 2005. We used an information theoretic approach to determine the variables that best predicted use by bats. Vegetation density at the sample point was the best predictor of overall bat presence in 2004. In 2005 vegetation density and distance to the closest road were the best predictors of overall bat use; the model containing age class also had good support. Bats were more likely to be recorded at points with sparse vegetation, farther from roads, and in early successional stands. Vegetation density was also the best predictor of habitat use by big brown bats (Eptesicus fuscus) and red bats (Lasiurus borealis); both species were far more likely to be recorded at points with sparse vegetation at the sample point. Eastern pipistrelles (Pipistrellus subflavus) were also more likely to be recorded at points with sparse vegetation and in early successional stands. The best predictors of northern long-eared bat (Myotis septentrionalis) habitat use were vegetation density and age class. Northern long-eared bats were more likely to be recorded at points with sparse vegetation and in mature stands. Our results suggest that early successional habitats and small openings and gaps within forest stands provide suitable commuting and foraging bat habitat in northwestern South Carolina. However, mature forests are also important for some species. Forest management practices that provide a variety of age classes across the landscape and that create gaps and openings within mid- and late-successional stands will likely provide suitable habitat for bats in the mountains of South Carolina.

Recent observations in the eastern United States suggest that bat communities can be at substantial risk of turbine-related mortality. Given that wind power development is the fastest growing energy sector in the world, there is an immediate need to develop survey protocols that can reliably assess the potential risk of future wind power development on both resident and migratory bat populations. I surveyed the Maple Ridge Wind Project site in New York, USA, during the spring migratory season and summer reproductive season using acoustic monitoring and mist net capture techniques. Bat activity was low across the project site during the summer months. The bats I observed at the site flew near the tree canopy, well below turbine height. Acoustic survey data collected during the spring migratory season suggests migratory behavior is highly episodic, being higher on warmer days with lower wind speeds. Knowledge of the influence of meteorological conditions on bat migration will require data on the spatial and temporal components of this behavior. Although acoustic monitoring using vertical acoustic arrays is currently limited to measuring the risk of bat mortality at wind development sites, it may be a valuable tool to increase our knowledge of the migratory phenology of bats.

Predicting potential habitat across a landscape for rare species is extremely challenging. However, partitioned Mahalanobis D² methods avoid pitfalls commonly encountered when surveying rare species by using data collected only at known species locations. Minimum habitat requirements are then determined by examining a principal components analysis to find consistent habitat characteristics across known locations. We used partitioned D² methods to examine minimum habitat requirements of Indiana bats (Myotis sodalis) in the Champlain Valley of Vermont and New York, USA, across 7 spatial scales and map potential habitat for the species throughout the same area. We radiotracked 24 female Indiana bats to their roost trees and across their nighttime foraging areas to collect habitat characteristics at 7 spatial scales: 1) roost trees, 2) 0.1-ha circular plots surrounding the roost trees, 3) home ranges, and 4–7) 0.5-km, 1-km, 2-km, and 3-km buffers surrounding the roost tree. Roost trees (n = 50) typically were tall, dead, large-diameter trees with exfoliating bark, located at low elevations and close to water. Trees surrounding roosts typically were smaller in diameter and shorter in height, but they had greater soundness than the roost trees. We documented 14 home ranges in areas of diverse, patchy land cover types that were close to water with east-facing aspects. Across all landscape extents, area of forest within roost-tree buffers and the aspect across those buffers were the most consistent features. Predictive maps indicated that suitable habitat ranged from 4.7–8.1% of the area examined within the Champlain Valley. These habitat models further understanding of Indiana bat summer habitat by indicating minimum habitat characteristics at multiple scales and can be used to aid management decisions by highlighting potential habitat. Nonetheless, information on juvenile production and recruitment is lacking; therefore, assessments of Indiana bat habitat quality in the region are still incomplete.

Changes in structure and arrangement of forests may influence the distribution of bat communities by affecting roosting and foraging habitat. Using Anabat bat detectors, we determined presence of bat species at 316 sample plots in southeastern Missouri, USA, through qualitative identification of echolocation calls collected. We used maximum-likelihood estimation techniques incorporating detection probabilities into estimation of site occupancy by species of bats. We compared a priori models at 2 geographic scales using information theoretic methods. At the local-site scale, eastern pipistrelle (Pipistrellus subflavus) and red bat (Lasiurus borealis) occupancy was most influenced by structural characteristics of forested areas, whereas Indiana bats (Myotis sodalis) were influenced most by density of large-diameter snags that could provide roosting habitat. At the landscape scale, occupancy of Indiana bats was directly related to amount of nonforested land cover. Northern long-eared bat (M. septentrionalis) occupancy was inversely related to edge. These data describe implications of forest fragmentation and provide information that can be used when integrating forest-management practices into bat conservation.

The study of habitat selection usually compares assessments of habitat use to habitat availability. To investigate habitat selection of large mammals today, researchers must choose between a few very expensive Global Positioning System (GPS) telemetry collars that can provide many locations and several inexpensive very high frequency telemetry collars that will provide few numbers of locations (unless substantial resources are spent in the field). We investigated the effects of number of locations and sampled animals on the outcome of habitat-selection analyses. We evaluated whether tracking frequency and sample size of individuals influenced our ability to detect habitat selection. We used data obtained from adult female moose fitted with GPS collars to generate data sets simulating various sampling frequencies and sample sizes of individuals. Tracking schedules conformed to those commonly used in ungulate telemetry studies (1 location every 14, 7, or 3 d and 1 or 3 locations per d) as did animal sample sizes (between 8 and 20 individuals). We determined habitat use and availability at the landscape and home-range scales during summer–autumn and winter. Precision of habitat use and availability estimates did not improve markedly with increasing tracking frequency. Only results obtained with the least-intensive tracking schedule (1 location every 14 d) differed from those obtained with the other schedules and only in 25% of the cases. Above this threshold in tracking frequency, number of sampled animals was clearly more important than number of locations in detection of habitat selection. Our results indicated that habitat-selection analyses were more sensitive to inter- than intra-individual variability. Depending on study objectives, it may be more profitable to prioritize number of sampled individuals rather than number of locations per individual. We suggest methods allowing researchers to assess inter-individual variability while studying habitat selection.

We examined the influence of year, habitat, and predators on nest survival by monitoring 69 natural cavity nests of the chestnut-backed chickadee (Poecile rufescens) across a range of uncut and partial cut stands in northwest British Columbia during 2000–2003. We considered 3 spatial scales of habitat: 1) the stand (19–24 ha of uncut and partial cut stands), 2) the nest patch (a 0.03-ha patch centered on nest trees), and 3) the nest tree. At each scale we hypothesized that nest survival time of chickadees differed among years, as a result of harvest treatment, habitat characteristics, and predator activity. Nest predation rates fluctuated among years: 56% in 2000, 64% in 2001, 10% in 2002, and 12% in 2003. We identified the red squirrel (Tamiasciurus hudsonicus) as the dominant nest predator. At the stand and nest patch scales, only the covariate year reliably predicted survival time: Risk = 1.81 (Year 2001) for both models. At the nest tree scale, we found the most support for a model with year and nest height: Risk = 1.67 (Year 2001) – 0.08 (Nest Height). All models indicated that for chickadees nesting in 2001, the probability of nest failure increased by more than 5 times. We found no effect of harvest treatment in the stand, nest patch, and nest tree models. Since squirrel density, space use, and activity near nest areas did not differ among years, we suggest that squirrels undergo a functional response and consume food items like eggs and nestlings following low mast years and cones following high mast years. Resource fluctuations that alter the availability and quality of food for red squirrels may result in strong variability in chickadee nest survival. Studies that do not consider such temporal variation may conclude that sites with low nest survival are sink habitats. Managers and researchers may need to consider longer term and/or multitrophic level studies to examine interactions among birds, their predators, and the environment.

In the Pacific Northwest, providing adequate habitat for pileated woodpeckers (Dryocopus pileatus) has been a key component of federal forest management strategies for over 20 years. Although their nesting and roosting ecology has been well studied, information on their foraging ecology is limited. From 1990 to 1995, we studied food habits of pileated woodpeckers in coastal forests (with scat analysis); estimated the relative abundance of their primary prey, carpenter ants (Camponotus spp.), associated with logs and cut stumps; and investigated selection of forest structures and site characteristics used by pileated woodpeckers for foraging. Pileated woodpeckers primarily consumed carpenter ants (54% of diet), but round-headed beetle larvae (Coleoptera, Cerambycidae) and dampwood termites (Isoptera, Termopsidae) were important food items during the breeding season (Mar–Jun). Selection of foraging structures was related to wood characteristics and microsite conditions that influence the presence and abundance of arthropod prey. Pileated woodpeckers foraged almost exclusively (95%) on standing structures, selecting tall, large-diameter snags in early to moderate stages of decay. Contrary to previous studies, pileated woodpeckers rarely (2%) foraged on logs. Carpenter ants were scarce at logs in closed-canopy habitats, which suggested that in coastal forests logs are too cool and wet to support abundant populations of carpenter ants. Selection of foraging sites by pileated woodpeckers was influenced by the abundance of potential foraging structures; 0.4-ha plots with recent foraging activity had greater densities of large snags (>51 cm dbh and ≥7.5 m tall) than plots without recent foraging. The efficacy of management strategies designed to provide habitat for pileated woodpeckers would be enhanced if they included specific provisions for foraging habitat and accounted for regional differences in the types of structures that provide suitable conditions for wood-dwelling arthropods.

Wildlife managers and farm program administrators need information on how much habitat grassland birds need to support or expand their populations. We quantified the relationships between the amount of Conservation Reserve Program (CRP) habitat in 15 agricultural landscapes and relative abundance of ring-necked pheasants (Phasianus colchicus), gray partridge (Perdix perdix), and meadowlarks (Sturnella spp.) in south-central Minnesota, USA, over a 10-year CRP enrollment cycle. For each 10% increase of grass in the landscape, pheasant survey counts increased by an average of 12.4 birds per route in spring and by 32.9 birds per route in summer. Pheasant indices also varied by year, and the magnitude of year effects were equivalent to a change in grass abundance of 26–36%. Regardless of the amount of grass habitat available, partridge indices in our study declined dramatically from a peak in 1990 to a low in 1994–1995. Meadowlark indices increased by an average of 11.7 birds per route in summer for each 10% increase of grass in the landscape, while indices simultaneously declined from 1990 to 1998. Our results indicate that conversion of cropland to CRP grassland in intensively cultivated landscapes is associated with higher population indices of pheasants and meadowlarks, but not partridge. Managers should assess the success of habitat programs over periods of ≥5 years because population indices may fluctuate dramatically over time with little apparent change in habitat abundance.

We investigated habitat use of the common warthog (Phacochoerus africanus) on a large, recently abandoned ranch in Tanzania. Fifty years of ranching had heavily modified the savanna vegetation, especially close to the paddocks where cattle were kept overnight. We recognized 4 characteristic vegetation zones along transects radiating from these paddocks: paddock center (PC), paddock margin (PM), acacia scrub (AS), and unmodified savanna (SV). Within these zones, we recorded warthog traces such as footprints, dung pellet groups, and diggings, and used these data to calculate presence and activity indices. Warthog traces were more abundant in the PM and AS than in PC and SV zones, and during dry periods the presence and activity indices were highest within and close to paddocks. From our results, we concluded that 1) warthogs are pioneer species, being one of the first native ungulates to recolonize cattle-impacted savanna vegetation; 2) areas close to former paddocks are particularly attractive to this species because of their vegetation structure and nutritional quality; 3) management to restore wildlife populations in former rangeland should initially focus on those areas where wildlife recolonization commences; and 4) indirect observations help to identify habitat-use patterns and point out key wildlife areas important for future protection.

Dispersal of yearling male white-tailed deer (Odocoileus virginianus) can have profound effects on population demographics and can adversely affect population estimates and management objectives. The relationship among population demographics, social pressures, and dispersal ecology is not clear and warrants scientific evaluation. The age structure and sex ratio of the white-tailed deer population at Chesapeake Farms, Maryland, USA, changed after implementation of quality deer management (QDM). Following Rosenberry's (1997) pre-QDM study on white-tailed deer dispersal, we conducted a post-QDM study on white-tailed deer dispersal at Chesapeake Farms. The objectives of our study were 1) to compare pre- and post-QDM emigration, immigration, survival, and behaviors of yearling males, 2) to evaluate inbreeding avoidance and sexual competition hypotheses as mechanisms of dispersal through behavioral comparisons of dispersers and nondispersers, and 3) to evaluate the maternal aggression hypothesis by comparing dispersal rates of orphan and non-orphan yearling males determined by genetic maternity analysis. Emigration probability of yearling males 8–18 months of age pre-QDM was 0.70 ± 0.07, and post-QDM was 0.54 ± 0.10 (Z = 1.39, P = 0.165). Survival probability of yearling males 8–18 months of age increased from 0.44 ± 0.07 pre-QDM to 0.72 ± 0.08 post-QDM (Z = 2.82, P = 0.005), and we attributed this increase largely to increased survival of emigrant males post-QDM. Dispersers exhibited breeding competition with other yearling males more often than nondispersers in both pre- (t₁₉ = 3.22, P = 0.005) and post-QDM (t₁₃ = 3.54, P = 0.004) populations. Breeding behaviors of yearling males decreased from pre- to post-QDM (t₃₄ = 2.00, P = 0.053). Antler points of nondisperser yearlings also decreased from pre- to post-QDM (t₁₆ = 3.29, P = 0.005). DNA maternity analysis indicated that dispersal of orphans (4 of 7) and non-orphans (7 of 10) was similar (= 0.298, P = 0.585). Our results fail to support inbreeding avoidance and support sexual competition as a cause of autumn dispersal at Chesapeake Farms. Through QDM, an older male age structure may have suppressed breeding competition in yearling males and decreased dispersal rates, increasing site-specific management efficiency

Although managers should strive to base game bird harvest management strategies on mechanistic population models, monitoring programs required to build and continuously update these models may not be in place. Alternatively, if estimates of total harvest and harvest rates are available, then population estimates derived from these harvest data can serve as the basis for making hunting regulation decisions based on population growth rates derived from these estimates. I present a statistically rigorous approach for regulation decision-making using a hypothesis-testing framework and an assumed framework of 3 hunting regulation alternatives. I illustrate and evaluate the technique with historical data on the mid-continent mallard (Anas platyrhynchos) population. I evaluate the statistical properties of the hypothesis-testing framework using the best available data on mourning doves (Zenaida macroura). I use these results to discuss practical implementation of the technique as an interim harvest strategy for mourning doves until reliable mechanistic population models and associated monitoring programs are developed.

The breeding stock composition and ecology of Canada (Branta canadensis) and cackling (B. hutchinsii) geese, collectively white-cheeked geese, staging in interior Alaska and wintering in the Pacific Northwest is poorly understood. We captured, measured, and applied neck collars to white-cheeked geese during spring and fall staging near Fairbanks and Delta Junction, Alaska, USA, to study their breeding stock composition, migration, and winter distribution. We measured exposed culmen, flattened wing chord, total tarsus, and body length of geese staging in interior Alaska to assist with determination of breeding stock. The first principal components, as well as a univariate measurement of exposed culmen, indicated geese trapped in Fairbanks in the fall were larger on average than geese trapped in Delta Junction in either spring or fall. We observed or recovered most of the banded geese detected in fall and winter in central British Columbia, Canada, central Washington, USA, and north-central Oregon, USA, east of the Cascade Mountains, with relatively few observations in western British Columbia, Washington, and Oregon. We found no evidence of movement between wintering areas on the east and west sides of the Cascade Mountains. Geese that we trapped during spring staging in Delta Junction were more often observed on the west side of the Cascade Mountains than geese trapped during fall staging in Fairbanks. Most (93%) geese trapped during fall staging in both Fairbanks and Delta Junction, however, wintered east of the Cascade Mountains. After-hatch-year (AHY) geese from interior Alaska staging areas observed on the west side of the Cascade Mountains were structurally smaller on average than AHY geese observed on the east side of the Cascade Mountains. Our results indicate fall staging white-cheeked geese in Fairbanks were predominantly 1 breeding stock of white-cheeked geese, while fall and spring staging white-cheeked geese in Delta Junction comprised at least 2 stocks of white-cheeked geese. Based on our findings, we recommend separate harvest and management strategies be considered for small white-cheeked geese migrating through coastal and central British Columbia and wintering east and west of the Cascade Mountains in Washington and Oregon to avoid potential overharvest of independent breeding stocks.

We collected 341 northern pintails (Anas acuta) along the lower Texas coast, USA, to investigate dynamics of carcass and digestive tract components during winter to help assess the ability of this region to support wintering pintail populations. Pintails relied more on endogenous lipid and protein reserves during winter of a dry year than a normal to wet year. Carcass fat remained relatively stable during the wet winter; however, pintails catabolized approximately 65% of their lipid reserves between arrival in October and departure at the end of February during the dry winter. Somatic protein mass also declined over both winters as pintails catabolized up to 20% of their muscle mass. Gizzard atrophy explained most of the changes in somatic protein during the wet winter, whereas catabolism of breast muscle also contributed to changes in protein mass during the dry winter. Ingesta-free digestive tract mass was greatest in early December, and then declined abruptly through February during both winters. Pintails departed the lower Texas coast in late February approximately 20% lighter in body mass than when they arrived in autumn. Mid-continent pintails may frequently opt to winter in southerly latitudes where they can maintain minimal endogenous reserves due to the moderate climate, limited human disturbance, and relatively dependable, but often lower-quality food resources. However, potential consequences of pintails initiating spring migration with reduced energy reserves include greater reliance on spring staging and breeding areas to meet their nutrient requirements for migration and reproduction, later arrival on breeding grounds, and reduced survival and reproductive success. Nutrient reserve dynamics of wintering, mid-continent pintails support the need for enhanced conservation of productive spring staging and breeding habitats for this population. It also provides additional concern over the loss of productive wintering sites along the western Gulf Coast.

We investigated the relationship between land use and mallard (Anas platyrhynchos) occupancy of single- and double-cylinder nest structures on a 658-km² (254-mile²) western Minnesota, USA, study area from 1997–1999. We used hierarchical logistic regression to spatio-temporally model structure occupancy as a function of land use, number of nearby structures, number of mallard pairs with access to the structure, size of the open-water area including the structure, and structure type. We fit models to data from 4 different-sized buffers around each structure to investigate scale influences. Goodness-of-fit, predictive ability, and amount of reduced spatio-temporal correlation were similar for each buffer-size model. We made inferences using the 1.6-km-radius buffer model because it produced the lowest deviance. The amount and attractiveness of nesting cover (i.e., as indexed by visual obstruction measurements [VOMs]) within a buffer interacted with nest-initiation period (P = 0.003). The VOMs and nest occupancy were positively associated early in the nesting season, but the pattern reversed later in the nesting season. Structure occupancy and area of open water around a structure were related quadratically (P = 0.004), with odds of a structure in median-sized open-water areas being occupied increasing until the open-water area was ~16 ha. Year and nesting-season period interacted (P = 0.002), reflecting different nest-initiation phenology. Number of pairs with access to a structure had no effect on nest initiations (P = 0.7), perhaps due to our inability to account for within-season changes in pair numbers. Number of nearby structures (P = 0.8) was unrelated to initiation probability, but structure density was low (0.05/km²). We suspect that mallard settling patterns and an unmeasured temporal relationship between VOMs and numbers of pairs with access to structures produced the VOM × period interaction. Structures deployed in larger open-water areas where surrounding residual upland cover is abundant can improve mallard nest success early in the nesting season when duckling survival is the greatest and can reduce hen mortality associated with nest destruction and re-nesting.

In studies of animal space use, researchers often use kernel-based techniques for estimating the size of an animal's home range and its utilization distribution from radiotracking data. However, the kernel estimator is highly sensitive to the bandwidth value used. Previous ecological studies recommended least-squares cross-validation (LSCV) as the default bandwidth selection method, but some statisticians consider this technique inferior to newer methods. We used simulations to compare the performance of the scaling LSCV and reference approaches to plug-in and solve-the-equation (STE) bandwidth methods. We generated samples of 20, 50, and 150 points from mixtures of 2, 4, and 16 bivariate normal distributions. We selected the ranges of potential variances for these distributions to create 4 distribution types with varied levels of clumping to simulate the diversity of location patterns expected from radiotracking data. For most distribution types, plug-in and STE methods performed as well or better than LSCV in % absolute error of home-range size estimates and overlap of estimated and true utilization distributions. Although the relative differences usually were small, the plug-in and STE approaches provide good alternatives to LSCV. However, LSCV performed better with distribution types composed entirely of tight clumps of points. The reference bandwidth performed poorly for most distributions. Surprisingly, it often had the lowest absolute error at outer contours for distributions consisting of a single very tight cluster surrounded by more dispersed points. Although our results demonstrate the utility of plug-in and STE approaches, no method was best across all distributions. Rather, choice of a bandwidth selection method may vary depending on the study goals, sample size, and patterns of space use by the study species. In general, we recommend plug-in and STE approaches for estimating relatively smooth outer contours. The LSCV approach is better at identifying tight clumps, including areas of peak use, although risk of LSCV failure also increases when a distribution has a very tight cluster of points. When planning to use kernel methods, researchers should consider these factors to make preliminary decisions about the bandwidth method expected to be most appropriate in their study.

The National Wildlife Strike Database for Civil Aviation in the United States contained 38,961 reports of aircraft collisions with birds (bird strikes) from 1990–2004 in which the report indicated the height above ground level (AGL). I analyzed these strike reports to determine the distribution of all strikes and those strikes causing substantial damage to aircraft by height. For the 26% of strikes above 500 feet (152 m) AGL (n = 10,143), a simple negative exponential model, with height as the independent variable, explained 99% of the variation in number of bird strikes per 1,000-foot (305-m) interval. Strikes declined consistently by 32% every 1,000 feet from 501–20,500 feet (153–6,248 m). For strikes at ≤500 feet, passerines, gulls and terns, pigeons and doves, and raptors were the identified species groups most frequently struck. For strikes at >500 feet, waterfowl, gulls and terns, passerines, and vultures were the species groups most frequently struck. For strikes that resulted in substantial damage to the aircraft, 66% occurred at ≤500 feet, 29% between 501–3,500 feet (153–1,067 m), and 5% above 3,500 feet. A higher (P < 0.001) proportion of strikes between 501–3,500 feet caused substantial damage to the aircraft (6.0%) than did strikes at ≤500 feet (3.6%) or at >3,500 feet (3.2%). For strikes at ≤500 feet, July–October were the months with the greatest proportion of strikes relative to aircraft movements. For strikes at >500 feet, September–November and April–May had more strikes than expected. About 61% of the reported strikes above 500 feet occurred at night, compared to only 18% of civil aircraft movements. Thus, about 7 times more strikes occurred per aircraft movement at night compared to day above 500 feet. This analysis confirmed that management programs to reduce strikes should focus on the airport environment because 74% of all strikes and 66% of strikes causing substantial damage occur at ≤500 feet. To minimize significant strike events occurring outside the airport (>500 feet), efforts to predict or monitor bird movements using bird avoidance models and bird-detecting radar need to focus on heights between 500 and 3,500 feet AGL, with special emphasis on night movements of birds during April–May and September–November.

White-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) occur sympatrically across much of the central and western United States, including portions of west Texas. Fluctuations in populations of both species and the potential for interspecific competition indicate a need for information to aid in management of sympatric populations. We evaluated the role of vegetation and topography on habitat use by sympatric deer in west-central Texas using a geographic information system. We captured and radiocollared 50 female mule deer, 53 female white-tailed deer, and 18 males of each species, and we monitored habitat use from February 2000 to August 2002 in west-central Texas. Mule deer primarily used juniper (Juniperus spp.)-dominated habitats and habitats with elevations >870 m. White-tailed deer home ranges primarily occurred in mesquite (Prosopis spp.)-dominated areas at elevations <840 m. However, overlap did occur, because individuals of both species used or avoided specific areas. Males of both species avoided areas with dense vegetation, including those containing permanent water sources, but females of both species selected such areas, particularly during summer fawning. We did not always detect the same differences observed on the smaller core area (50% kernel home range) scale at the larger home range level, indicating that individuals made decisions about habitat use at different spatial scales. Given the differential importance of various vegetation associations to the establishment of core areas of each sex and species, maintenance of a mosaic of vegetation, particularly in lower-elevation areas and in proximity to food and permanent water, is necessary for managers to perpetuate coexistence of both species. Managers should target habitat conditions of overlap areas, particularly in core areas, for determination of potential limiting factors for both species since competition is mostly likely to occur in these areas.

Succession of stream ponds mediated by beaver (Castor canadensis) damming and foraging in riparian zones may contribute to changes in amphibian populations. Our study examined the use of beaver ponds by the wood frog (Rana sylvatica) in a network of boreal streams in west-central Alberta, Canada. We quantified relations between breeding populations of wood frogs estimated from call surveys and pond age and riparian canopy cover, and we compared an index of juvenile recruitment to metamorphosis estimated with pitfall trap captures between new (<10 yr) and old (>25 yr) beaver ponds. We also conducted an in-pond enclosure experiment to determine if differences in physicochemical conditions of new versus old ponds influenced larval performance. Regression and Akaike's Information Criterion model averaging indicated that both density and calling intensity of male wood frogs at beaver ponds had a negative relationship with percent riparian canopy cover and had a positive relationship with pond age. The best a priori statistical models, however, included riparian canopy cover rather than pond age as a significant covariate. Old ponds had reduced riparian canopy and greater abundance of submergent vegetation, thermal degree-days, and dissolved oxygen concentrations compared to newly formed ponds. While survival of larval wood frogs in enclosures did not differ between pond age classes, growth and development rates in old ponds were greater than in new ponds. In addition to warmer water in old ponds, results from a laboratory experiment suggest that higher concentrations of dissolved oxygen characteristic of old ponds can enhance larval growth rates. Older beaver ponds may support more breeding wood frogs due to adult selection for open-canopy ponds and the associated larval environments favourable for high rates of juvenile recruitment. Forest management that protects beaver and their food supplies may also promote healthy populations of boreal amphibians.

Counts of northern Yellowstone elk (Cervus elaphus) in northwestern Wyoming and adjacent Montana, USA, have decreased at an average rate of 6–8% per year since wolves (Canis lupus) were reintroduced in 1995. Population growth rates of elk are typically sensitive to variations in adult female survival; populations that are stable or increasing exhibit high adult female survival. We used survival records for 85 radiocollared adult female elk 1–19 years old to estimate annual survival from March 2000 to February 2004. Weighted average annual survival rates were approximately 0.83 (95% CI = 0.77–0.89) for females 1–15 years old and 0.80 (95% CI = 0.73–0.86) for all females. Our estimates were much lower than the rate of 0.99 observed during 1969–1975 when fewer elk were harvested by hunters, wolves were not present, and other predators were less numerous. Of 33 documented deaths included in our analysis, we attributed 11 to hunter harvest, 14 to predation (10 wolf, 2 unknown, 1 cougar [Puma concolor], and 1 bear [Ursus sp.]), 6 to unknown causes, and 2 to winter-kill. Most deaths occurred from December through March. Estimates of cause-specific annual mortality rates were 0.09 (0.05–0.14) for all predators, 0.08 (0.04–0.13) for hunting, and 0.07 (0.03–0.11) for wolves specifically. Wolf-killed elk were typically older (median = 12 yr) than hunter-killed elk (median = 9 yr, P = 0.03). However, elk that winter outside the park where they were exposed to hunting were also younger (median = 7 yr) than elk that we did not observe outside the park (median = 9 yr, P < 0.01). Consequently, differences in ages of elk killed by wolves and hunters may reflect characteristics of elk exposed to various causes of mortality, as well as differences in susceptibility. Unless survival rates of adult females increase, elk numbers are likely to continue declining. Hunter harvest is the only cause of mortality that is amenable to management at the present time.

We investigated how changes in vegetation structure and prey resources following wildfire affected the winter ecology of hairy woodpeckers (Picoides villosus) in ponderosa pine (Pinus ponderosa) forests of northern Arizona, USA. Using point-counts, radiotelemetry, and focal bird observation, we assessed the relative abundance, home range size and composition, and habitat use by foraging hairy woodpeckers in 3 stands that had experienced wildfire in 1996, 2000, or 2002. Because we conducted the study over 2 years, we used the 1996 fire to represent 6 and 7 years after fire, while we used the 2000 fire to represent 2 and 3 years after fire in a space-for-time substitution chronosequence analysis. We also assessed bark beetle and woodborer density by x-raying bark samples collected from a subset of trees within burned areas. We detected significantly greater hairy woodpecker relative abundance in burned forests representing 1 and 2 years after fire, and bark beetle and woodborer density was highest in these stands as well. Woodpecker home range size increased across stands representing increasing time since fire. Within a burn, hairy woodpeckers used high-severity burned areas more than moderate-severity burned areas representing 2 and 3 years after fire, but not in areas representing 6 and 7 years after fire. Bark beetle and woodborer densities were also higher in high-severity burned stands representing 2 and 3 years after fire. Hairy woodpeckers used edges of high-severity burned areas more than the interior. We hypothesize that an initial increase in bark beetle and woodborer density following fire allowed for higher woodpecker abundance and smaller home ranges, but as burned forests aged, bark beetle and woodborer density within trees decreased, killed trees fell, and, in response, hairy woodpecker relative abundance decreased and home range size increased. These patterns suggest that high-severity burned areas provide important but ephemeral resources to this dominant primary cavity-nester. The higher bark beetle and woodborer densities and greater use of edges of high-severity burned areas by woodpeckers suggests that salvage logging of these areas could remove potential prey and preferred foraging areas for hairy woodpeckers, especially when trees are removed along severely burned edges.

We evaluated an unverified index (auditory counts) used to estimate breeding populations of white-winged doves (Zenaida asiatica) in Texas, USA. Our objectives were to determine optimal survey time of day, year, and count duration, determine if a relationship existed between number of calling doves and population size (nest and dove density), and evaluate an electronic counter to estimate breeding density. We collected data on 15 sites in the Lower Rio Grande Valley of Texas during May–August of 2002–2003. Peak calling occurred between mid-May and late June during 0600–0800 hours. We detected about 60% of calling doves during 2-minute auditory counts. Estimates of breeding doves (pairs ha⁻¹) as determined by auditory counts were positively correlated with both population density (r > 0.90, P < 0.01) and nest density (r > 0.94, P < 0.01). The electronic coo-counter tally also exhibited a positive relationship with population density (r > 0.77, P < 0.01) and nest density (r > 0.92, P < 0.04). However, the high correlations observed for auditory counts and electronic counter were influenced by 2 high dove-density sites. Our data did not provide convincing support for the premise underlying auditory counts of white-winged doves (i.e., number of doves calling reflects dove abundance). The electronic coo counter was limited in application because it tabulated dove calls based solely on acoustic frequency and therefore could not discriminate against other avian calls with acoustic frequencies similar to those of white-winged doves. Auditory counts may be appropriate as coarse-resolution reconnaissance surveys to locate new white-winged dove areas in need of monitoring but not to obtain reliable abundance estimates. The use of an electronic counter to estimate breeding populations of white-winged doves holds promise, given technical modifications, and warrants further research. Given the current limitations of both auditory counts and electronic counters, alternative survey methods that incorporate detection probabilities (e.g., distance sampling) need to be evaluated for white-winged doves.

We investigated the influence of habitat use on the risk of death of Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Heceta Island in Southeast Alaska, USA. A mosaic of even and uneven-aged forests covered much of the island and provided a model setting in which to assess relationships between habitat use and mortality of deer. We radiocollared and monitored 51 adult females, 11 adult males, and 19 young of the year. We compared risk of death with habitat composition, habitat distribution, topography, distances to features such as roads, and functional habitat characteristics such as seasonal forage biomass within 50-, 500-, and 1,000-m circular buffers around relocations of deer. Those buffers encompassed habitats used at scales of radio-locations, home ranges, and landscapes. We addressed hypotheses that related habitat composition and distribution to risk of death from malnutrition, predation, and hunting. Predation by wolves (Canis lupus) and malnutrition were the principal causes of death of adult females and young, whereas hunters killed most adult males. Habitat factors at scales of 500 and 1,000 m had the greatest effect on mortality of adult females and young, whereas habitat characteristics in the immediate vicinity of radio relocations had the greatest effect on mortality of adult males. Malnutrition was positively associated with use of forage-poor habitats such as pole-stage, second-growth forest. Use of precommercially thinned second growth increased risk of death for young deer. Use of level terrain was the most influential factor with respect to predation and increased risk of death at all scales. Use of open habitats, such as muskegs and young clearcuts, also increased risk of death. Use of shrub-sapling-stage clearcuts in landscapes accessible by roads increased risk of death from hunting. We showed that use of specific habitats and the landscape context of those habitats were important factors influencing mortality of deer. We also demonstrated the importance of comparing habitat use with measures of fitness rather than simply with availability when evaluating habitat suitability for deer. Our results should be useful to wildlife researchers investigating contributions of habitat to fitness and population dynamics of ungulates, and to wildlife managers attempting to manipulate habitats to benefit deer populations.

Bottomland hardwood forests of the southeastern United States support a rich avifauna, including >20 species of conservation concern; understanding the impact of land use practices on these communities is critical to their conservation. Selective timber harvesting is a common management practice in southern bottomland hardwood forests, but little research has examined impacts >5 years after harvesting. We studied breeding bird communities in selectively harvested bottomland forests in northeastern Louisiana during 2003–2004. We conducted point counts in recently harvested stands (1–5 yr postharvest) and older harvests (12–18 yr postharvest); we paired each with a reference stand that had not been harvested for >30 years. Of 35 species with sufficient detections for analysis, we found evidence that abundances of 17 species differed among treatments. Three species were sensitive to creation of canopy openings by timber harvests, including 2 species of concern in the Mississippi Alluvial Valley, USA, prothonotary warbler (Protonotaria citrea) and Acadian flycatcher (Empidonax virescens). However, 4 species of concern often associated with densely vegetated canopy gaps were more abundant in older harvests than in reference stands: Swainson's warbler (Limnothlypis swainsonii), hooded warbler (Wilsonia citrina), white-eyed vireo (Vireo griseus), and Kentucky warbler (Oporornis formosus). As expected, a suite of species typically associated with shrub and forest-edge habitats was more abundant in recent harvests than in reference stands. We conclude that selective logging has a strong influence on bird abundances in both recent and older harvests in bottomland forests. With the exception of Acadian flycatcher, older harvests and reference stands supported similar abundances of the species typically found in closed-canopy bottomland forests. In addition, older harvests supported substantially higher abundances of gap-dependent species than other treatments. Our results should be useful to land managers and conservation planners evaluating short- and long-term effects of timber management practices on breeding birds in the Mississippi Alluvial Valley. However, measures of breeding productivity are necessary to evaluate more fully the habitat quality of harvested forests.

Urbanization threatens the persistence of many wildlife populations, particularly those of wide-ranging and low-density species such as mammalian carnivores. Effective conservation of carnivore populations requires an understanding of the impacts of adjacent urbanization on carnivores in reserves. I compared the spatial ecology of bobcats (Lynx rufus) and gray foxes (Urocyon cinereoargenteus) between urban and rural zones of a national park in northern California, USA. In the urban zone, gray foxes used the entire landscape from interior natural areas across the park edges and into the neighboring developed areas, although fox core areas were always within the park. Bobcats never entered development, and radiocollared adult female bobcats maintained home ranges in the interior of the park, far from the urban edge. Bobcats appeared to avoid crossing paved roads, while foxes crossed roads regularly. For adult female bobcats, home ranges were smaller in the urban zone, and core areas were both smaller and overlapped more. Home range size and overlap did not differ between zones for gray foxes. Bobcats seem to be more affected by the proximity of urbanization than foxes, perhaps because of differences in diet and social structure. The more flexible use of the landscape by foxes may give them access to increased resources and habitat, but also may expose them to more human-associated risks. If female bobcats are more sensitive to urbanization, this sensitivity could affect the long-term viability of bobcat populations in urban areas. Knowledge of how bobcats and gray foxes use the landscape in urban areas will allow more effective conservation and improved coexistence with these widespread carnivores by helping to predict where and why conservation or management issues may occur.

We used radiotelemetry to study mallard (Anas platyrhynchos) brood movements, wetland use, and duckling survival during a major drought (1988–1992) and during the first 2 years of the subsequent wet period (1993–1994) at 4 51-km² sites in prairie pothole landscapes in eastern North Dakota, USA. About two-thirds of 69 radiomarked mallard broods initiated moves from the nest to water before noon, and all left the nest during daylight. On average, broods used fewer wetlands, but moved greater distances during the dry period than the wet period. Broods of all ages were more likely to make inter-wetland moves during the wet period and probabilities of inter-wetland moves decreased as duckling age increased, especially during the dry period. Brood use of seasonal wetlands nearly doubled from 22% to 43% and use of semi-permanent wetlands declined from 73% to 50% from the dry to the wet period. Eighty-one of 150 radiomarked ducklings died during 1,604 exposure days. We evaluated survival models containing variables related to water conditions, weather, duckling age, and hatch date. Model-averaged risk ratios indicated that, on any given date, radiomarked ducklings were 1.5 (95% CI = 0.8–2.8) times more likely to die when the percentage of seasonal basins containing water (WETSEAS) was ≤18% than when WETSEAS was >40%. An interaction between duckling age and occurrence of rain on the current or 2 previous days indicated that rain effects were pronounced when ducklings were 0–7 days old but negligible when they were 8–30 days old. The TMIN (mean daily minimum temperature on the current and 2 previous days) effects generally were consistent between duckling age classes, and the risk of duckling death increased 9.3% for each 1°C decrease in TMIN across both age classes. Overall, the 30-day survival rate of ducklings equipped with radiotransmitters was about 0.23 lower than the survival rate of those without radiotransmitters. Unmarked ducklings were 7.6 (95% CI = 2.7–21.3) times more likely to die on any given day when WETSEAS was ≤18% than when WETSEAS was >40%. Higher duckling survival and increased use of seasonal wetlands during the wet period suggest that mallard production will benefit from programs that conserve and restore seasonal wetland habitat. Given adverse effects of low temperatures on duckling survival, managers may want to include this stochastic variable in models used to predict annual production of mallards in the Prairie Pothole Region.

Many high-density populations of wild ungulates have exerted strong negative impacts on their habitat. A decrease in forage quantity and quality may affect individual growth, fecundity, and survival, especially under harsh winter conditions. On Anticosti Island, Québec, Canada, browsing by introduced white-tailed deer (Odocoileus virginianus) negatively affected boreal forest composition. Since the preferred contemporary winter forage of deer, balsam fir (Abies balsamea), has been almost completely extirpated from the island at browse height, deer are forced to increase the proportion of normally avoided forage, such as white spruce (Picea glauca), in their winter diet. We predicted that an increase in the proportion of white spruce in the diet would have detrimental effects on deer body condition and would affect their behavior and life history traits. We experimentally simulated a deterioration of winter forage quality in semi-natural enclosures by increasing the proportion of white spruce in the diet and examined the effects of winter diet quality on 1) forage intake, 2) body condition loss, 3) activity budget, and 4) survival of white-tailed deer fawns. Fawns fed the poor-quality diet maintained a higher forage intake rate throughout the winter than fawns fed the control diet, suggesting a compensatory response to the decrease of forage quality by consuming more forage during winter. Body mass decreased over the winter, but we did not observe any significant effects of diet quality on body mass loss. Diet quality did not influence the activity budget of fawns, but deer decreased activity in cold weather. The main determinant of overwinter survival was individual body mass in early winter. Our study suggests that deer have adapted to the extreme conditions encountered on Anticosti (i.e., harsh and long winters, low-quality browse, and a high-density population). Even though white spruce stands are gradually replacing balsam fir stands, our results suggest that deer on Anticosti could maintain a high-density population by increasing the amount of white spruce in their diet. However, future studies are necessary to address the long-term effects of a diet dominated by white spruce on deer body condition, survival, and reproduction under natural conditions.

Our objective was to estimate demographic parameters and population trends for Swainson's hawks (Buteo swainsoni) breeding in southeast Alberta and southwest Saskatchewan, Canada, from 1972 to 2003. We assembled mark–resighting–recovery histories of 6,606 banded Swainson's hawks for a joint analysis of survival and resighting probability, including band-reporting rate and fidelity of animals, following Burnham's joint resighting–recovery model provided in program MARK. Our best-fitting survival model specified age-related variation in survival, resighting probability, and fidelity, and it specified age-by-temporal variation in nestling survival and adult resighting probability. From estimated survival rates and previously published data on reproduction, for the period 1973–1996 we estimated the population's finite rate of increase, λ, to be 0.996 (95% CI: 0.945–1.057). We believe that population limitation of Swainson's hawks is primarily related to the influence of prey availability on brood size and nestling survival. Despite indications of recent population declines, we conclude that Swainson's hawks breeding in western Canada are not currently in need of special management action.