Characteristics of Occupied and Unoccupied Loggerhead Shrike Territories in Southeastern Alberta

• Published in: The Journal of wildlife management 1993-04, Vol.57 (2), p.346-352
• Main Authors: David R. C. Prescott, Collister, Douglas M.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal reproduction; Animal, plant and microbial ecology; Animals; Aves; Biological and medical sciences; Birds; Breeding; Breeding sites; Demecology; Depopulation; Discriminants; Forests; Fundamental and applied biological sciences. Psychology; Grasses; Habitat loss; Habitat selection; Habitats; Lanius ludovicianus; Shrubs; Vertebrata; Wildlife habitats
• ISSN: 0022-541X; 1937-2817
• DOI: 10.2307/3809432

Population declines in loggerhead shrikes (Lanius ludovicianus) are most frequently blamed on habitat limitation. Thus, we compared structural characteristics of loggerhead shrike territories in southeastern Alberta with characteristics of visually similar, but unoccupied, sites in the same area. We predicted that if reproduction in this threatened population is limited by habitat availability, then occupied and unoccupied sites should consistently differ along ≥ 1 structural dimension. Stepwise discriminant function analysis (DFA) identified 5 of 15 habitat variables that were potential discriminators (P < 0.05) of site occupancy by shrikes. Canonical DFA showed that these 5 variables discriminated between occupied and unoccupied sites with 98.4% accuracy. Occupied sites contained a higher percentage of tall (≥20 cm) grass, and had a higher mean height of grass than unoccupied sites. We suggest that loggerhead shrikes may be limited by habitat in southeastern Alberta, and that the availability of suitable habitat for breeding could be increased by management practices that increase the prevalence of tall grass.