干旱区生态环境知识资源中心

Loggerhead Shrikes (Lanius ludovicianus) have declined throughout much of their range over the past few decades. Management plans to address these declines require information on habitat requirements throughout the species’ range. Despite this, there has been very little study on territory requirements or foraging habitat of Loggerhead Shrikes at the northern limits of their distribution. Here, we examined territory sizes, foraging habitat, and hunting success of shrikes in southeastern Alberta during the 1992 and 1993 breeding seasons. Territories averaged 8.5 ha (95% Minimum Convex Polygon) and were smaller in 1992 than 1993, but did not differ in size between incubation and nestling periods. Territory sizes were larger than those found in many core areas of the species’ range, perhaps because this region is more arid and supports lower prey abundance. Foraging success was highest on the highway/railway right-of-way, followed by native pastures, and was lowest in crop fields, fallow fields, and improved pastures. Despite this, shrikes foraged less often than expected on the right-of-way, perhaps because tall, dense cover makes foraging there energetically expensive. Foraging shrikes also avoided crop and fallow fields in favor of native and improved pastures. Management strategies should take into account the larger territory requirements of shrikes in this part of their distribution. Based on territory sizes and foraging habitat use, we recommend limiting habitat disturbance within approximately 250 m of nest sites and maintaining native pasture on known shrike territories.