Aim Our objective was to identify the distribution of the endangered golden-cheeked warbler (Setophaga chrysoparia) in fragmented oak–juniper woodlands by applying a geoadditive semiparametric occupancy model to better assist decision-makers in identifying suitable habitat across the species breeding range on which conservation or mitigation activities can be focused and thus prioritize management and conservation planning. Location Texas, USA. Methods We used repeated double-observer detection/non-detection surveys of randomly selected (n = 287) patches of potential habitat to evaluate warbler patch-scale presence across the species breeding range. We used a geoadditive semiparametric occupancy model with remotely sensed habitat metrics (patch size and landscape composition) to predict patch-scale occupancy of golden-cheeked warblers in the fragmented oak–juniper woodlands of central Texas, USA. Results Our spatially explicit model indicated that golden-cheeked warbler patch occupancy declined from south to north within the breeding range concomitant with reductions in the availability of large habitat patches. We found that 59% of woodland patches, primarily in the northern and central portions of the warbler’s range, were predicted to have occupancy probabilities ≤0.10 with only 3% of patches predicted to have occupancy probabilities >0.90. Our model exhibited high prediction accuracy (area under curve = 0.91) when validated using independently collected warbler occurrence data. Main conclusions We have identified a distinct spatial occurrence gradient for golden-cheeked warblers as well as a relationship between two measurable landscape characteristics. Because habitat-occupancy relationships were key drivers of our model, our results can be used to identify potential areas where conservation actions supporting habitat mitigation can occur and identify areas where conservation of future potential habitat is possible. Additionally, our results can be used to focus resources on maintenance and creation of patches that are more likely to harbour viable local warbler populations.
Wildlife biologists use knowledge about wildlife‐habitat relationships to create habitat models to predict species occurrence across a landscape. Researchers attribute limitations in predictive ability of a habitat model to data deficiencies, missing parameters, error introduced by specifications of the statistical model, and natural variation. Few wildlife biologists, however, have incorporated intra‐ and interspecific interactions (e.g., conspecific attraction, competition, predator‐prey relationships) to increase predictive accuracy of habitat models. Based on our literature review and preliminary data analysis, conspecific attraction can be a primary factor influencing habitat selection in wildlife. Conspecific attraction can lead to clustered distributions of wildlife within available habitat, reducing the predictive ability of habitat models based on vegetative and geographic parameters alone. We suggest wildlife biologists consider incorporating a parameter in habitat models for the clustered distribution of individuals within available habitat and investigate the mechanisms leading to clustered distributions of species, especially conspecific attraction.
Summary 1.Research on habitat selection has focused on the role of vegetative and geologic characteristics or antagonistic behavioural interactions. 2. Conspecifics can confer information about habitat quality and provide positive densitydependent effects, suggesting habitat selection in response to the presence of conspecifics can be an adaptive strategy. 3. We conducted a manipulative field experiment investigating use of conspecific location cues for habitat selection and consequent reproductive outcomes for the endangered golden-cheeked warbler (Setophaga chrysoparia). We investigated the response in woodlands across a range of habitat canopy cover conditions typically considered suitable to unsuitable and using vocal cues presented during two time periods: pre-settlement and post-breeding. 4. Warblers showed a strong response to both pre-settlement and post-breeding conspecific cues. Territory density was greater than four times higher in treatment sample units than controls. The magnitude of response was higher for cues presented during the pre-settlement period. Positive response to conspecific cues was consistent even in previously unoccupied areas with low canopy cover typically considered unsuitable, resulting in aggregations of warblers in areas generally not considered potential habitat. 5. Pairing and reproductive success of males was not correlated with canopy cover, as commonly thought. Pairing success and fledging success increased with increasing territory density suggesting that conspecific density may be more important for habitat selection decisions than the canopy cover conditions typically thought to be most important. These results suggest the range of habitat within which birds can perform successfully may be greater than is typically observed. 6. Our results suggest the territory selection process may not be substantially influenced by competition in some systems. Settlement in response to conspecific cues produced aggregations within larger areas of similar vegetative characteristics. Understanding what cues drive habitat selection decisions and whether these cues are correlated with habitat quality is critical for conserving fitness-enhancing habitats, avoiding creation of ecological traps, generating accurate predictions of species distributions and understanding how occupancy relates to habitat suitability.
. Using LiDAR-derived vegetation metrics for high-resolution, species distribution models for conservation planning. Ecosphere 4(3):42. http://dx.doi.org/10.1890/ES12-000352.1Abstract. Advances in remotely sensed data for characterizing habitat have enabled development of spatially explicit predictive species distribution models (SDM) that can be essential tools for management. SDMs commonly use coarse-grain metrics, such as forest patch size or patch connectivity, over broad spatial extents. However, species distributions are likely driven in part by local, fine-grained habitat conditions. Conservation and management are often planned and applied locally, where coarse predictions may be uninformative or not sufficiently precise. We investigated the integration of high-resolution LiDAR (Light Detection and Ranging) with avian point sampling data to develop a detection-corrected occupancy model to quantify habitat-occurrence relationships for two species with different habitats: the endangered golden-cheeked warbler (Setophaga chrysoparia) and black-capped vireo (Vireo atricapilla) on a military installation in central Texas. We compared occupancy models that used only the more conventional, coarse remotely sensed metrics to models that also incorporated high-resolution LiDAR-derived metrics for vegetation height and canopy cover, to assess their use for predicting distributions. Models including LiDAR-derived vegetation height and canopy cover metrics were competitive for both species, and models without LiDAR-derived vegetation height had substantially lower model weights and explanatory strength. Area under curve estimates for the highest ranked models were high for warblers (0.864) and moderate for vireos (0.746). Using the best supported models for each species, we predicted the occurrence distribution for both species. The resulting predictions provide a decision support tool that enables assessment of the status, impacts, and mitigation of impacts to endangered species habitat on the installation due to land management and military training activities that is more standardized and accurate than current assessment approaches based on visual gestalt of habitat and expert opinion. Additionally, although previous species distribution models have been created for our focal species, most fail to match the grain and extent of most management actions or include local, fine-grained metrics that influence distributions. In contrast, we demonstrate that use of LiDAR with species occurrence data can provide precision and resolution at a scale that is relevant ecologically and to the operational scale of most conservation and management actions.
Conservation actions for the federally and provincially threatened Bobolink (Dolichonyx oryzivorus) in Ontario, Canada are ongoing in agricultural landscapes, including pastures. However, conditions conducive to Bobolink fledging young from breeding territories in rotationally grazed beef cattle (Bos taurus) pastures are not well understood. We tested two management strategies designed to provide habitat where Bobolink could fledge young in rotationally grazed pastures. We conducted (1) a refuge paddock experiment using a crossover design, comparing fledging success when paddocks were ungrazed in one year to when they were grazed in another year; and (2) a light spring grazing experiment. Additionally, we explored associations between fledging of young from territories with cattle stocking rate and date that cattle first entered paddocks. We used spot mapping and nest monitoring to determine if young fledged in 83 Bobolink territories in 2016 and 72 territories in 2017 on six farms in the Ottawa Valley, Ontario. In the refuge paddock experiment, 54% (N = 28) of Bobolink territories fledged young in eight ungrazed paddocks compared to 16% (N = 25) when these paddocks were grazed in another breeding season. In the light spring grazing experiment, 67% (N = 12) of territories fledged young from four paddocks that were grazed with a low stocking rate between 21 May and 03 June 2017 and not again until after 02 July. Additionally, predictions from a logistic regression model indicated that the probability of young fledging from a territory (N = 118) decreased from 0.53 to 0.04 when mid-season stocking rates increased from 0 to 174 cattle-days/ha. Our results illustrate that paddocks on rotationally grazed beef cattle farms that are ungrazed until the Bobolink breeding season is finished or grazed lightly for a brief duration soon after territories are established can provide areas that enable Bobolink to fledge young. Rotation des pâturages de b!ufs pour soutenir le succès de nidification du Goglu des prés RÉSUMÉ. Des activités de conservation visant le Goglu des prés (Dolichonyx oryzivorus), espèce menacée au niveaux fédéral et provincial en Ontario, Canada, ont cours dans les paysages agricoles, y compris les pâturages. Toutefois, on ne comprend pas bien les conditions qui favorisent l'envol des jeunes goglus de territoires de nidification situés dans des pâturages de b!ufs (Bos taurus) sous rotation. Nous avons testé deux stratégies de gestion visant à fournir de l'habitat dans lequel les goglus pouvaient mener leurs jeunes à l'envol dans des pâturages sous rotation. Nous avons effectué (1) une expérience d'enclos-refuge au moyen d'un plan d'étude croisé, comparant le succès de jeunes à l'envol lorsque des enclos ne servaient pas de pâturage une année à celui lorsque les enclos servaient de pâturage une autre année; et (2) une expérience de pâturage printanier léger. De plus, nous avons exploré les relations entre l'envol de jeunes et la densité de bétail, et la date à laquelle le bétail entrait dans l'enclos. Nous ...
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