David A. Steen

Bird assemblage response to restoration of fire‐suppressed longleaf pine sandhills

The ecological restoration of fire-suppressed habitats may require a multifaceted approach. Removal of hardwood trees together with reintroduction of fire has been suggested as a method of restoring fire-suppressed longleaf pine (Pinus palustris) forests; however, this strategy, although widespread, has not been evaluated on large spatial and temporal scales. We used a landscape-scale experimental design to examine how bird assemblages in fire-suppressed longleaf pine sandhills responded to fire alone or fire following mechanical removal or herbicide application to reduce hardwood levels. Individual treatments were compared to fire-suppressed controls and reference sites. After initial treatment, all sites were managed with prescribed fire, on an approximately two- to three-year interval, for over a decade. Nonmetric multidimensional scaling ordinations suggested that avian assemblages on sites that experienced any form of hardwood removal differed from assemblages on both fire-suppressed sites and reference sites 3-4 years after treatment (i.e., early posttreatment). After >10 years of prescribed burning on all sites (i.e., late posttreatment), only assemblages at sites treated with herbicide were indistinguishable from assemblages at reference sites. By the end of the study, individual species that were once indicators of reference sites no longer contributed to making reference sites unique. Occupancy modeling of these indicator species also demonstrated increasing similarity across treatments over time. Overall, although we documented long-term and variable assemblage-level change, our results indicate occupancy for birds considered longleaf pine specialists was similar at treatment and reference sites after over a decade of prescribed burning, regardless of initial method of hardwood removal. In other words, based on the response of species highly associated with the habitat, we found no justification for the added cost and effort of fire surrogates; fire alone was sufficient to restore these species.

Landscape-level influences of terrestrial snake occupancy within the southeastern United States.

Habitat loss and degradation are thought to be the primary drivers of species extirpations, but for many species we have little information regarding specific habitats that influence occupancy. Snakes are of conservation concern throughout North America, but effective management and conservation are hindered by a lack of basic natural history information and the small number of large-scale studies designed to assess general population trends. To address this information gap, we compiled detection/nondetection data for 13 large terrestrial species from 449 traps located across the southeastern United States, and we characterized the land cover surrounding each trap at multiple spatial scales (250-, 500-, and 1000-m buffers). We used occupancy modeling, while accounting for heterogeneity in detection probability, to identify habitat variables that were influential in determining the presence of a particular species. We evaluated 12 competing models for each species, representing various hypotheses pertaining to important habitat features for terrestrial snakes. Overall, considerable interspecific variation existed in important habitat variables and relevant spatial scales. For example, kingsnakes (Lampropeltis getula) were negatively associated with evergreen forests, whereas Louisiana pinesnake (Pituophis ruthveni) occupancy increased with increasing coverage of this forest type. Some species were positively associated with grassland and scrub/shrub (e.g., Slowinskis cornsnake, Elaphe slowinskii) whereas others, (e.g., copperhead, Agkistrodon contortrix, and eastern diamond-backed rattlesnake, Crotalus adamanteus) were positively associated with forested habitats. Although the species that we studied may persist in varied landscapes other than those we identified as important, our data were collected in relatively undeveloped areas. Thus, our findings may be relevant when generating conservation plans or restoration goals. Maintaining or restoring landscapes that are most consistent with the ancestral habitat preferences of terrestrial snake assemblages will require a diverse habitat matrix over large spatial scales.

ASSESSING THE SENSITIVITY OF WETLAND BIRD COMMUNITIES TO HYDROLOGIC CHANGE IN THE EASTERN GREAT LAKES REGION

Uncertainty about the effects of ongoing natural and anthropogenic changes to Great Lakes ecosystems, such as managed stabilized water levels, coupled with widespread public interest regarding status of wetland birds prompted us to evaluate sensitivity of regional wetland birds to hydrologic changes. We reviewed published literature to determine preferred habitat of 30 wetland birds in the region, emphasizing vegetation required for foraging and nesting during the breeding season. Species were subsequently assigned to one of three risk categories based on association with vegetation types sensitive to water-level stabilization, as well as nesting height above water. Notably, of the bird species designated as low, moderate, and high risk, 25%, 33%, and 63%, respectively, have been regionally declining based on Bird Studies Canada’s Marsh Monitoring Program. This evaluation may be useful to regional biologists, planners, and managers concerned with predicting how particular species might be affected by future hydrologic changes in this and related systems.

Snake co‐occurrence patterns are best explained by habitat and hypothesized effects of interspecific interactions

Snakes often occur in species-rich assemblages, and sympatry is thought to be facilitated primarily by low diet overlap, not interspecific interactions. We selected, a priori, three species pairs consisting of species that are morphologically and taxonomically similar and may therefore be likely to engage in interspecific, consumptive competition. We then examined a large-scale database of snake detection/nondetection data and used occupancy modelling to determine whether these species occur together more or less frequently than expected by chance while accounting for variation in detection probability among species and incorporating important habitat categories in the models. For some snakes, we obtained evidence that the probabilities that habitat patches are used are influenced by the presence of potentially competing congeneric species. Specifically, timber rattlesnakes (Crotalus horridus) were less likely than expected by chance to use areas that also contained eastern diamond-backed rattlesnakes (Crotalus adamanteus) when the proportion of evergreen forest was relatively high. Otherwise, they occurred together more often than expected by chance. Complex relationships were revealed between habitat use, detection probabilities and occupancy probabilities of North American racers (Coluber constrictor) and coachwhips (Coluber flagellum) that indicated the probability of competitive exclusion increased with increasing area of grassland habitat, although there was some model uncertainty. Cornsnakes (Pantherophis guttatus or Pantherophis slowinskii) and ratsnakes (Pantherophis alleghaniensis, Pantherophis spiloides, or Pantherophis obsoletus) exhibited differences in habitat selection, but we obtained no evidence that patterns of use for this species pair were influenced by current interspecific interactions. Overall, our results are consistent with the hypothesis that competitive interactions influence snake assemblage composition; the strength of these effects was affected by landscape-scale habitat features. Furthermore, we suggest that current interspecific interactions may influence snake occupancy, challenging the paradigm that contemporary patterns of snake co-occurrence are largely a function of diet partitioning that arose over evolutionary time.

The Vertebrate Fauna of Ichauway, Baker County, GA

Abstract Less than 4% of the once extensive Pinus palustris (longleaf pine) ecosystem remains today. Although longleaf pine habitats are recognized for their high species diversity, few published accounts document the vertebrate faunas of remaining tracts. Here we report on the vertebrate species richness of Ichauway, an 11,300-ha property in Baker County, GA. The property includes ca. 7300 ha of longleaf pine with native ground cover, along with more than 30 seasonal wetlands and ca. 45 km of riparian habitat associated with Ichawaynochaway Creek, Big Cypress Creek, and the Flint River. The fauna includes 61 species of fish, 31 amphibians, 53 reptiles, 191 birds, and 41 mammals. Despite the relative isolation of the property from other natural ecosystems, the vertebrate fauna of Ichauway is remarkably diverse and may offer an example of reference conditions to guide restoration of longleaf pine forests, associated seasonal wetlands, and riparian areas elsewhere in the southeastern US.

Habitat Use of Sympatric Rattlesnake Species Within the Gulf Coastal Plain

Abstract The eastern diamondback rattlesnake (Crotalus adamanteus) and timber rattlesnake (Crotalus horridus) are sympatric throughout most of southern Georgia, USA. We used rattlesnake sightings to quantify and compare habitat use by these 2 species in the Gulf Coastal Plain. At the largest scale examined, univariate statistics and logistic regression models indicated that eastern diamondback rattlesnakes were associated with roads but not with any of the specific habitat types we examined. In contrast, timber rattlesnakes were closely associated with hardwood habitat and riverine systems but not with roads and edges. To effectively conserve and manage both species in the Southeast, a habitat matrix of large intact patches of both hardwood and pine (Pinus spp.) forest may be necessary.

Multiscale Habitat Selection and Refuge Use of Common Kingsnakes, Lampropeltis getula, in Southwestern Georgia

Abstract The Common Kingsnake, Lampropeltis getula, is thought to be experiencing population declines in the southeastern portion of its geographic range. However, limited information exists regarding the natural history and habitat requirements of the species in this region. We conducted a radio-telemetry study to investigate habitat selection in L. getula at multiple scales in southwestern Georgia. At the home range scale, L. getula did not show habitat selection. However, at the study-area scale, L. getula selected for natural pine and hardwood forest types over other available habitats. At the microhabitat scale, L. getula were found in locations with more coarse woody debris and woody vegetation than random sites. Lampropeltis getula primarily used small mammal (Peromyscus spp.) burrows and stumpholes as below ground refuge sites. We demonstrate that habitat selection of L. getula is complex and occurs at multiple scales.

Terrestrial Movements and Microhabitat Selection of Overwintering Subadult Eastern Mud Turtles (Kinosternon subrubrum) in Southwest Georgia

Abstract Although there is increasing recognition of the importance of terrestrial habitat to aquatic fauna, little is known about the specific habitat requirements of these species at a fine scale within the terrestrial landscape. Our knowledge of subadult life stages of many species, specifically aquatic turtles, is particularly depauperate. We used radio-telemetry to determine the timing and extent of terrestrial movements of 11 subadult Eastern Mud Turtles, Kinosternon subrubrum, during the winter. We also quantified microhabitat variables (ground cover composition, shrub cover, and canopy cover) of temporary refugia and overwintering sites (hibernacula) of radio-tagged turtles. On average, hibernacula sites were 72 m from the wetland (defined as the waters edge). Turtles remained at hibernacula a mean of 107 days before emerging in the spring. Radio-tagged turtles selected winter hibernacula with a large component of leaf and pine litter and less tree cover than temporary refugia. The leaf litter may provide stable temperature and soil moisture at hibernacula for overwintering turtles, whereas the open canopy may expose turtles to relatively higher temperatures in the spring prior to emergence.

An Overlooked Hotspot? Rapid Biodiversity Assessment Reveals a Region of Exceptional Herpetofaunal Richness in the Southeastern United States

Abstract We conducted a competitive bioblitz survey in four Georgia counties to raise awareness of a unique and species rich herpetofauna in the Pine Mountain/ Fall Line Sandhills Region of Georgia, and compared documented species of these counties to other herpetofaunas of the southeast that have known high richness and/ or were subject to thorough collection efforts. Our results demonstrate the efficacy of bioblitzes for documenting large numbers of species in a limited amount of time (62 amphibian and reptile species in only seven days, including 36 new county records and documentation of three protected species). Compared to areas of similar size, this area is among the most species-rich herpetofaunas in North America north of Mexico, with only three areas having higher documented richness. However, all areas we compared our site to have experienced much higher collection effort and contain much larger tracts of protected land. Thus, our data suggest the Pine Mountain/Fall Line Sandhills region is among the most important regions for amphibian and reptile conservation in North America.

Effects of Forest Management on Amphibians and Reptiles: Generalist Species Obscure Trends Among Native Forest Associates

In the future, land stewards are expected to increase their use of fire surrogates to manage longleaf pine forests. Varying land management strategies may have disparate effects on wildlife and the strength of these effects may depend upon the degree to which each target species is associated with the longleaf pine forest. To determine how amphibian and reptile assemblages respond to prescribed burns and fire surrogates, we sampled these animals within plots of land managed under four common management practices (burning, thinning, thinning and burning, and application of herbicide) and on unmanaged reference plots. We analyzed these data first by examining the entire herpetofauna and then by repeating all analyses for only taxa exhibiting some evidence of an evolutionary association with longleaf pine forests. We found that estimates of species richness of all amphibians did not differ significantly among treatments. These trends were altered when the pool of taxa was restricted to amphibian species known to be associated with longleaf pine forests. For associated amphibians, species richness was elevated on plots that were exposed to herbicide and burn, hardwood thinning, and hardwood thinning plus prescribed fire, relative to reference plots. No significant trends were identified for squamates in general or those squamate species known to be associated with longleaf forests. Fire surrogates may facilitate conservation for individual species of the ancestral biota of longleaf pine forests, but these trends may be obscured when entire assemblages are considered.