IntroductionMultifarious selective pressures can interact to affect species’ life history evolution, with predation and thermal exposure as selective pressures for nesting birds. Gray Vireos (Vireo vicinior) seemingly nest on the periphery of their nesting substrate because of lower predation rates, thereby increasing exposure to weather. We explored how nest placement and vegetation structure can be used to account for the increased weather exposure that Gray Vireos experience when nesting on the periphery of the nesting substrate to avoid predation.MethodsFor each Gray Vireo nest, we placed temperature and light data loggers at three locations: at the nest site, at the opposite orientation of the nest within the nesting tree, and at the same orientation of the nest but in an adjacent tree. To measure nest orientation, we recorded the inverse compass azimuth (+/−1°) from the nest toward the trunk of the nesting tree, while accounting for declination. Nest temperatures and light exposure were compared across various dimensions of nest placement.ResultsThe orientation of nests was cooler than the opposite orientation in the mornings and in the late afternoons. When nests were placed in hotter orientations (e.g., south- or west-facing), nests surrounded by more foliage or placed closer to the interior of trees could compensate for the increased exposure.DiscussionOur findings suggest Gray Vireos accounted for the increased thermal exposure that comes from predator avoidance by using secondary dimensions of nest placement. Specifically, nests could be placed in orientations with cooler temperatures or in hotter orientations with greater shade potential. These results highlight how the interactive selection pressures of predation risk and microclimate can be tiered and shape life-history characteristics of birds.

Predictions of species occurrence allow land managers to focus conservation efforts on locations where species are most likely to occur. Such analyses are rare for herpetofauna compared to other taxa, despite increasing evidence that herptile populations are declining because of landcover change and habitat fragmentation. Our objective was to create predictions of occupancy and colonization probabilities for 15 herptiles of greatest conservation need in Iowa. From 2006-2014, we surveyed 295 properties throughout Iowa for herptile presence using timed visual-encounter surveys, coverboards, and aquatic traps. Data were analyzed using robust design occupancy modeling with landscape-level covariates. Occupancy ranged from 0.01 (95% CI = -0.01, 0.03) for prairie ringneck snake (Diadophis punctatus arnyi) to 0.90 (95% CI = 0.898, 0.904) for northern leopard frog (Lithobates pipiens). Occupancy for most species correlated to landscape features at the 1-km scale. General patterns of species' occupancy included negative effects of agricultural features and positive effects of water features on turtles and frogs. Colonization probabilities ranged from 0.007 (95% CI = 0.006, 0.008) for spiny softshell turtle (Apalone spinifera) to 0.82 (95% CI = 0.62, 1.0) for western fox snake (Pantherophis ramspotti). Colonization probabilities for most species were best explained by effects of water and grassland landscape features. Predictive models had strong support (AUC > 0.70) for six out of 15 species (40%), including all three turtles studied. Our results provide estimates of occupancy and colonization probabilities and spatial predictions of occurrence for herptiles of greatest conservation need across the state of Iowa.

Predators can significantly limit the amount of available habitat for vulnerable prey. Encouraging spatial segregation of predators and prey through habitat management prescriptions may be a useful tool to increase productivity and abundances of prey species of conservation concern. We estimated the total area of low-risk nesting habitat by interacting predator habitat selection models with northern bobwhite (Colinus virginianus) nest-site selection models. We used trail cameras, transect sampling, spotlighting transects, and incidental tracking to survey and map occurrences of mesopredators at a site in western Oklahoma, USA. We created broad-scale resource selection function models for bobwhite nest-site and mesopredator habitat selection using generalized linear models to create maps of occurrence probability in ArcGIS. Bobwhite nests were more likely to be depredated in areas of high selection by coyotes (Canis latrans) and striped skunks (Mephitis mephitis) compared to areas with low mesopredator selection. Approximately 392 ha of bobwhite nesting habitat (17%) had low probabilities of selection by both coyotes and striped skunks. Our results demonstrate the need for incorporating species' interactions into estimations of available habitat. Based on the total area of highly selected cover by northern bobwhite, approximately 29% of the study area would have been deemed suitable for nesting. However, only 5% of that area is predicted to have a low predation risk.

The Pollard-Yates transect is a widely used method for sampling butterflies. Data from these traditional transects are analyzed to produce density estimates, which are then used to make inferences about population status or trends. A key assumption of the Pollard-Yates transect is that detection probability is 1.0, or constant but unknown, out to a fixed distance (generally 2.5 m on either side of a transect line). However, species-specific estimates of detection probability would allow for sampling at farther distances, resulting in more detections of individuals. Our objectives were to (1) evaluate butterfly density estimates derived from Pollard-Yates line transects and distance sampling, (2) estimate how detection probabilities for butterflies vary across sampling distances and butterfly wing lengths, and (3) offer advice on future butterfly sampling techniques to estimate population density. We conducted Pollard-Yates transects and distance-sampling transects in central Iowa in 2014. For comparison to densities derived from Pollard-Yates transects, we used Program DISTANCE to model detection probability (p) and estimate density (D) for eight butterfly species representing a range of morphological characteristics. We found that detection probability among species varied beyond 2.5 m, with variation apparent even within 5 m of the line. Such variation correlated with wing size, where species with larger wing size generally had higher detection probabilities. Distance sampling estimated higher densities at the 5-m truncation for five of the eight species tested. At this truncation, detection probability was <0.8 for all species, and ranged from 0.53 to 0.79. With the exception of the little yellow (Pyrisitia lisa), species with median wing length <5.0 mm had the lowest detection probabilities. We recommend that researchers integrate distance sampling into butterfly sampling and monitoring, particularly for studies utilizing survey transects >5 m wide and when smaller species are targeted.

Habitat fragmentation and heterogeneity transform otherwise contiguous tracks of forest into smaller patches in the northeastern U.S. and likely impact abundances, movement patterns, and disease transmission pathways for small-mammal communities at multiple scales. We sought to determine the structure of a small-mammal community in terms of mammal abundance and infection prevalence of Borrelia burgdorferi sensu stricto (s.s.), Anaplasma phagocytophilum, and Babesia microti within a fragmented landscape in Essex County, Massachusetts, USA. We studied communities at multiple spatial scales, including vegetation, edge type, and landscape (including 200-m, 500-m, and 1000-m radii) scales. A total of 16 study sites were chosen to represent four edge types: interior forest, pasture edge, natural edge, and residential edge. At each site, we trapped small mammals and conducted vegetation surveys and GIS analysis. Upon capture, a tissue sample was collected to analyze for presence of pathogens. Northern short-tailed shrew (Blarina brevicauda) abundance did not differ based on edge type, whereas abundance of the white-footed mouse (Peromyscus leucopus) was greatest at pasture edges, although the relationship was relatively weak. White-footed mouse abundance was negatively associated with amount of forested area within a 500-m radius, whereas northern short-tailed shrew abundance demonstrated a positive relationship with fragmentation indices at the 200-m radius. White-footed mice captured at interior-forest habitat were more likely be infected with B. burgdorferi (s.s.) than individuals from edge habitat. Greater prevalence of B. burgdorferi infection of white-footed mice in forest interiors compared to edge habitats counters previous studies. Reasons for this and implications are discussed.

Habitat management efforts for multiple species with contrasting habitat requirements can be challenging, particularly on small landscapes where large-scale heterogeneity may not be a viable solution. We sought to utilize derivative functions from species-response curves to identify thresholds along an environmental gradient for two species with differing responses to juniper cover. We estimated percentages of one-seed juniper (Juniperus monosperma) cover around loggerhead shrike (Lanius ludovicianus) and gray vireo (Vireo vicinior) nests in central New Mexico in 2016-2020 to better understand tolerance of juniper expansion for these two species of con-servation concern. Species-response curves were derived from generalized additive mixed-effect models, with year as a random effect and a local regression smoother. Loggerhead shrike nests were more likely to occur in areas without junipers at the 170-m radius spatial scale. Nest-site selection declined as percent juniper cover increased. Gray vireo nests were most likely to be found in areas with approximately 11 % juniper cover at the 100-m radius spatial scale. Derivative functions were used to find juniper percentages where the rate of change in species' response was most negative for loggerhead shrikes and most positive for gray vireos. The rate of change in nest-site selection decreased the fastest at 13 % and increased the fastest at 4 % juniper cover for loggerhead shrike and gray vireo, respectively. These results suggest that maintaining juniper percentages between 4 and 13 % at relatively broad spatial scales would likely increase available nesting habitat both species. We demonstrate how derivative functions can be used to estimate the rate of change of species' response to environmental gra-dients and an application of such thresholds to resolve conflicting habitat management for two species of con-servation concern.

Common approaches to estimating habitat quality are habitat suitability indices, which are often subjective. We propose a quantitative definition of habitat quality as the percentage of selected habitat that has a high probability of contributing to population growth. Using this definition, we created a habitat quality index based on spatial projections of habitat selection and survival probabilities, and the interaction of those probability gradients. We used nest-site selection and nest survival of Gray Vireos (Vireo vicinior) to represent habitat selection and survival probabilities of a sensitive life stage that is likely to increase population size. We used data from 173 Gray Vireo nests in central New Mexico to estimate selection and survival probabilities. Generalized linear mixed-effect models (GLMM) and logistic exposure models (LEM) were used to estimate nest-site selection and daily nest survival, respectively. We projected top-ranked GLMM and LEM models in a geographic information system (GIS) to spatially display relative probabilities of selection and survival. We converted these continuous probabilities into binary rasters representing high and low selection and survival. Multiplying these two rasters in ArcGIS provided us with a raster of four categories: areas with i) low selection and low survival, ii) low selection and high survival, iii) high selection and low survival, and iv) high selection and high survival. We determined the spatial area of each category and calculated percentage of selected habitat where survival was likely to occur, which we termed a habitat quality index (HQI). At our study site, Gray Vireos had a HQI of 0.85, suggesting that approximately 85% of the highly selected habitat had a high probability of contributing to Gray Vireo population growth through nest survival, and that few ecological traps exist in this landscape. These methods provide a quantifiable, continuous index of habitat quality, with spatial projections of potential ecological trap locations.

Understanding the interactions between behavior and habitat characteristics can have important implications for species of conservation concern. Gray vireos ( Vireo vicinior ) are one example of a species of conservation concern that is understudied in terms of nest survival probabilities and the habitat characteristics that influence them. Our objective was to determine if habitat features such as juniper density, juniper foliage density, or tree height influence nest survival probabilities, and if gray vireo nest placement can mitigate habitat risks. Based on previous work, we expected daily nest survival probabilities to be associated with nest height and surrounding vegetation. We monitored 89 nests in central New Mexico from 2016–2018 to estimate daily nest survival probabilities. We compared variation in nest placement, nest tree characteristics, and surrounding vegetation between failed and successful nests using logistic exposure models and Akaike Information Criteria. Daily and cumulative nest survival probability were 0.983 (95% CI [0.973–0.989]) and 0.575 (95% CI [0.444–0.702]), respectively. Top models predicting nest survival included a negative interaction between nest-tree foliage density and the distance of the nest from the edge of the nesting tree. This suggests that gray vireos can mitigate risks associated with low nest concealment by nesting closer to the interior of the nesting tree.

There are many gaps in our understanding of Gray Vireo (Vireo vicinior) life history especially as it relates to nesting ecology. Our objective was to determine habitat features selected by Gray Vireos for nesting to improve management strategies for breeding populations. We searched for Gray Vireo nests on Kirtland Air Force Base in Albuquerque, New Mexico from 2016 to 2017. We estimated Gray Vireo nest-site selection at the tree level, the surrounding vegetation, and at two broader scales corresponding to selection within territories. Nest-site selection was estimated for 99 Gray Vireo nests. For tree-level selection, we compared characteristics of nesting trees with mean characteristics from groups of six randomly selected one-seed junipers (Juniperus monosperma) within a 25-m radius. We also compared overall vegetation characteristics at the 25-m scale for nesting plots and 66 randomly selected plots. Broad-scale cover proportions of nest sites and random points were estimated at 50- and 100-m radius spatial scales using a geographic information system. Gray Vireos selected nesting trees that were taller and wider than other adjacent junipers. Selection of vegetation characteristics surrounding nests showed a similar pattern, where Gray Vireos nested in areas where junipers were taller, wider, and had greater foliage density than was randomly available. Broad-scale analyses suggested that Gray Vireos selected nest sites in areas with higher proportions of junipers at low elevations (< 1954 m), and lower proportions of junipers in higher elevations (> 1954 m); however, juniper proportions at nest sites consistently ranged from 15 to 30% of available cover. Gray Vireos also tended to select areas with less pinyon pine than what was randomly available at the 100-m radius scale. Future management strategies should provide large patches of old-growth juniper to optimize Gray Vireo nesting habitat.

Numerous studies have documented that invertebrate pollinator services are critical to the world economy. Factors including habitat loss and agricultural practices, however, threaten pollinator populations. Many counties in the Southern High Plains were identified as at risk for a shortage of pollination service from wild bees. This region also has one of the highest concentrations of Conservation Reserve Program (CRP) contracts in the US. The CRP is the largest, voluntary, private lands conservation program in the US and was targeted as a program to improve pollinator habitat. Our objective was to determine how the predominant land uses in the SHP (native grassland, CRP, and cropland) affect pollinator abundance and species richness, and more specifically if the CRP can provide quality habitat for pollinators. We also examined how the keystone habitat, playa wetlands, embedded within these land uses contribute to pollinator habitat (land type: uplands vs. wetland). We used blue vane traps placed in playa basins and adjacent uplands to determine Hymenoptera abundance and richness from April to October in 2013 and 2014. The CRP had lower abundance than cropland and native grassland, and generally less richness. Uplands and playa wetlands had little difference in Hymenoptera abundance and richness. Patch size negatively influenced abundance but had a positive influence on richness. The interaction of vegetation height and percent bare ground positively influenced abundance in cropland and native grasslands, and positively influenced richness in all land uses. In the CRP, vegetation height negatively influenced Hymenoptera abundance and percent bare ground had a positive influence. The years sampled in this study were during a severe extended drought; therefore, these results may be reflective of poor floral resources. The CRP has potential to create valuable habitat for pollinators if land managers incorporate a diversity of native grasses and native forbs into plantings to enhance pollinator foraging and nesting habitat.

In southern New England forests, small mammals provide essential contributions to ecosystem functioning via food-web interactions and seed dispersal. This region has been exposed to extensive habitat fragmentation due to residential and agricultural development, resulting in a considerable amount of edge habitat, in addition to naturally occurring landscape heterogeneity. Limited research has been conducted relating small-mammal species richness and abundance to different types of edge habitat in this region. Studies incorporating an analysis of variation in both fine-scale vegetation and coarse-scale landscape variation are even more limited. We compared small-mammal richness, total abundance, and abundance of Peromyscus maniculatus (Deer Mouse), Peromyscus leucopus (White-footed Mouse), Myodes gapperi (Red-backed Vole), Tamias striatus (Eastern Chipmunk), and Tamiasciurus hudsonicus (Eastern Red Squirrel) at developed-edge, wetland-edge, and forest-interior sites. We also measured vegetation and landscape variables to understand how variation in characteristics at different scales affected small-mammal measures. We selected 4 sites of each edge type and used Sherman live-traps during the summers of 2009-2010 to survey small-mammal populations (75 traps for 4 nights at 12 sites for 2 y = 7200 trap-nights). We did not find differences among edge types and interior forest for total abundance, richness, and abundance of the 5 small-mammal species with sufficient data for analysis. However, vegetation variables and landscape variables were significantly associated with small-mammal populations. Step-wise linear regression included vegetation variables for 4 of the 5 species, and various landscape scales were included in all analyses except abundance of Peromyscus adults. Patch size was included in 4 analyses (positive for total abundance, White-footed Mouse, and Red-backed Vole; negative for Eastern Chipmunk). We found conifer basal area to have a positive relationship with abundance of Peromyscus adults and Red-backed Voles, but a negative relationship with abundance of Peromyscus juveniles and Eastern Red Squirrels. Species abundance and richness of small-mammal communities and populations in northeastern Massachusetts were related to both fine-scale vegetation differences and coarse-scale landscape metrics, but these relationships were complex and scale-dependent.