The importance of mature conifers to red crossbills in southeast Alaska

Abstract

Red crossbills ( Loxia curvirostra) in southeast Alaska feed mostly on seeds in the cones of western hemlock ( Tsuga heterophylla) and Sitka spruce ( Picea sitchensis). During a year of poor cone production, red crossbills did not forage in young stands. Within mature stands, crossbills tended to forage preferentially on trees with large cone crops. These favored trees were also the larger and older trees because cone production increases with tree size. The avoidance of young stands is especially pronounced during poor seed years and may be related to the absence of mature trees containing numerous cones with many seeds. We suggest that mature stands are critical for maintaining crossbill populations and possibly other conifer seed-eating species.