Multiscale occupancy of the Lesser Prairie-Chicken: the role of private lands in conservation of an imperiled bird

Grasslands are one of the most imperiled ecosystems globally, and the Lesser Prairie-Chicken (Tympanuchus pallidicinctus) is an iconic grassland-obligate species with high conservation priority in the USA. Lesser Prairie-Chicken conservation is compounded by its requirement for a spatial hierarchy of heterogeneous habitats, coupled with nearly all (> 95%) of its range being privately owned. The U.S. Department of Agriculture currently offers technical and financial resources that facilitate prairie restoration, e.g., Conservation Reserve Program (CRP), and improve habitat quality and ecosystem services, e.g., Environmental Quality Improvement Program, on private lands. We modeled Lesser Prairie-Chicken occupancy at two scales relative to covariates that described landscape composition and configuration, anthropogenic development, drought-related climatic conditions, and conservation efforts from 2012 to 2016. Large-scale (225 km²) occupancy was most associated with shrubland, grassland patch size, and CRP range-wide. Patterns of small-scale (56.25 km²) occupancy varied regionally, but key covariates included shrubland, grassland, and CRP landcover. These covariate relationships may be useful for identifying conservation practices at different spatial scales and habitat factors that influence Lesser Prairie-Chicken distributions ecoregionally. Notably, CRP-enrolled lands appear to serve as a surrogate for prairie habitat in some ecoregions, especially in conjunction with larger extant patches of native habitat. Although not as influential as CRP at large scales, every 2.25 km² of prescribed grazing increased the odds of site occupancy by 11%. In addition to supported covariates, we found that for every 0.56 km² of industrial development at small scales and 2.25 km² of woodland cover (10%-canopy) at large scales, odds of occupancy decreased by 22% and 13%, respectively. Our results suggest that increased amounts of native grassland and shrubland, and in particular higher levels of CRP enrollment could expand LEPC distribution by as much as 17% (1418-1744 km²). Moreover, our findings illustrate the potential for federal conservation policies to benefit the distribution of an imperiled species

Does avian species richness in natural patch mosaics follow the forest fragmentation paradigm?

As one approaches the north-eastern limit of pinyon (Pinus spp.) juniper (Juniperus spp.) vegetation on the Colorado Plateau, USA, woodland patches become increasingly disjunct, grading into sagebrush (Artemisia spp.)-dominated landscapes. Patterns of avian species richness in naturally heterogeneous forests may or may not respond to patch discontinuity in the same manner as bird assemblages in fragmented agricultural systems. We used observational data from naturally patchy woodlands and predictions derived from studies of human-modified agricultural forests to estimate the effects of patch area, shape, isolation and distance to contiguous woodland on avian species richness. We predicted that patterns of species richness in naturally patchy juniper woodlands would differ from those observed in fragmented agricultural systems. Our objectives were to (1) estimate the effect of naturally occurring patch structure on avian species richness with respect to habitat affinity and migratory strategy and (2) assess the concordance of the effects to predictions from agricultural forest systems. We used the analogy between populations and communities to estimate species richness, where species are treated as individuals in the application of traditional capture-recapture theory. Information-theoretic model selection showed that overall species richness was explained primarily by the species area relationship. There was some support for a model with greater complexity than the equilibrium theory of island biogeography where the isolation of large patches resulted in greater species richness. Species richness of woodland-dwelling birds was best explained by the equilibrium hypothesis with partial landscape complementation by open-country species in isolated patches. Species richness within specific migratory strategies showed concomitant increases and no shifts in species composition along the patch area gradient. Our results indicate that many patterns of species richness considered to be fragmentation effects may be general consequences of patch discontinuity and are ubiquitous in naturally heterogeneous systems. There was no evidence for the effects of patch shape and distance to contiguous woodland in juniper woodland, suggesting edge effects and dependence upon regional species pools are characteristics of fragmented agricultural systems. Natural patch mosaics may provide benchmarks for evaluating fragmentation effects and managing forests by mimicking natural landscape patterns

Habitat quality and geometry affect patch occupancy of two Orthopteran species

Impacts of habitat loss and fragmentation on distribution and population size of many taxa are well established. In contrast, less is known about the role of within-patch habitat quality for the spatial dynamics of species, even though within-patch habitat quality may substantially influence the dynamics of population networks. We studied occurrence patterns of two Orthopteran species in relation to size, isolation and quality of habitat patches in an intensively managed agricultural landscape (16.65 km(2)) in the Swiss lowland. Occurrence of field crickets (Gryllus campestris) was positively related to patch size and negatively to the distance to the nearest occupied patch, two measures of patch geometry. Moreover, field crickets were more likely to occur in extensively managed meadows, meadows used at low intensity and meadows dominated by Poa pratensis, three measures of patch quality. Occurrence of the large gold grasshopper (Chrysochraon dispar) was negatively related to two measures of patch geometry, distance to the nearest occupied patch and perimeter index (ratio of perimeter length to patch area). Further, large gold grasshoppers were more likely to occupy patches close to water and patches with vegetation left uncut over winter, two measures of patch quality. Finally, examination of patch occupancy dynamics of field crickets revealed that patches colonized in 2009 and patches occupied in both 2005 and 2009 were larger, better connected and of other quality than patches remaining unoccupied and patches from which the species disappeared. The strong relationships between Orthopteran occurrence and aspects of patch geometry found in this study support the "area-and-isolation paradigm". Additionally, our study reveals the importance of patch quality for occurrence patterns of both species, and for patch occupancy dynamics in the field cricket. An increased understanding of patch occupancy patterns may be gained if inference is based on variables related to both habitat geometry and quality