The ecology and conservation of a small endemic population of red crossbill

Knowledge of the ecological factors that influence avian habitat use is critical for making proper management decisions. This is particularly true for species whose populations are limited by the availability of suitable habitat. The South Hills crossbill (Loxia curvirostra complex) is endemic to the South Hills and Albion Mountains of southern Idaho, and is locally adapted for foraging on the distinctive cones of lodgepole pine (Pinus contorta latifolia) in these two ranges. The South Hills crossbill is presumably limited to this area because its bill is poorly adapted relative to that of other crossbills for foraging on other conifers elsewhere. Given the limited suitable habitat available, its conservation is of concern.;In order to improve our understanding of South Hills crossbill ecology and make informed management recommendations, I quantified food resource availability, nest site selection, and habitat preferences. An estimate of seasonal variation in energy demands for this crossbill demonstrated that seed predation by this species likely drives the seasonal variation in seed availability, causing the crossbill population to be regulated. Documentation of the characteristics of preferred nest sites indicated that South Hills crossbills most often nested in mature, relatively open conifer stands dominated by lodgepole pine, with high foliage densities in the upper canopy. An analysis of habitat features at different spatial scales and comparison with crossbill abundance and evidence of crossbill cone predation indicated that South Hills crossbills were most abundant year-round in relatively open, mature lodgepole pine stands, which likely provided increased food profitability and protection from potential predators.;The long-term survival of the South Hills crossbill is reliant on the maintenance of robust lodgepole pine stands. Given our current knowledge, this is most likely to be achieved by (1) protecting healthy lodgepole stands from timber harvest, (2) expanding lodgepole pine reforestation and establishing relatively open reforested patches in order to maximize seedling survival and growth rate, (3) mitigating fire danger by reducing understory fuel loads, and (4) minimizing the potential for pine bark beetle infestations and arboreal disease outbreaks by reducing the density of overcrowded stands and removing infected trees.