title: Using Field Data and GIS-Derived Variables to Model Occurrence of Williamson's Sapsucker Nesting Habitat at Multiple Spatial Scales.
abstract: Williamson's sapsucker (Sphyrapicus thyroideus) is a migratory woodpecker that breeds in mixed coniferous forests in western North America. In Canada, the range of this woodpecker is restricted to three small populations in southern British Columbia, precipitating a national listing as 'Endangered' in 2005, and the need to characterize critical habitat for its survival and recovery. We compared habitat attributes between Williamson's sapsucker nest territories and random points without nests or detections of this sapsucker as part of a resource selection analysis to identify the habitat features that best explain the probability of nest occurrence in two separate geographic regions in British Columbia. We compared the relative explanatory power of generalized linear models based on field-derived and Geographic Information System (GIS) data within both a 225 m and 800 m radius of a nest or random point. The model based on field-derived variables explained the most variation in nest occurrence in the Okanagan-East Kootenay Region, whereas nest occurrence was best explained by GIS information at the 800 m scale in the Western Region. Probability of nest occurrence was strongly tied to densities of potential nest trees, which included open forests with very large (diameter at breast height, DBH, ≥57.5 cm) western larch (Larix occidentalis) trees in the Okanagan-East Kootenay Region, and very large ponderosa pine (Pinus ponderosa) and large (DBH 17.5-57.5 cm) trembling aspen (Populus tremuloides) trees in the Western Region. Our results have the potential to guide identification and protection of critical habitat as required by the Species at Risk Act in Canada, and to better manage Williamson's sapsucker habitat overall in North America. In particular, management should focus on the maintenance and recruitment of very large western larch and ponderosa pine trees.
authors.affiliation: Canadian Wildlife Service, Environment Canada, Delta, British Columbia, Canada; Centre for Applied Conservation Research, Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Drever
authors.affiliation: Okanagan Wildlife Consulting, West Kelowna, British Columbia, Canada.
authors.forename: Les W
authors.initials: LW
authors.lastname: Gyug
authors.affiliation: Centre for Applied Conservation Research, Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nielsen
authors.affiliation: Canadian Forest Products Ltd., Cranbrook, British Columbia, Canada.
authors.forename: A Kari
authors.initials: AK
authors.lastname: Stuart-Smith
authors.affiliation: Consulting Biologists, Kimberley, British Columbia, Canada.
authors.forename: I Penny
authors.initials: IP
authors.lastname: Ohanjanian
authors.affiliation: Canadian Wildlife Service, Environment Canada, Delta, British Columbia, Canada; Centre for Applied Conservation Research, Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Kathy
authors.initials: K
authors.lastname: Martin
mesh_terms: D000818:Animals; D001717:Birds; D017753:Ecosystem; D040362:Geographic Information Systems; D008962:Models, Theoretical; D009425:Nesting Behavior; D062206:Spatial Analysis