Distribution and Habitat Selection of Canyon Wrens, Lower Salmon River, Idaho

Abstract

Because canyon wrens (Catherpes mexicanus) are among the least-studied avian species in North America, we sought to obtain detailed data on distribution and habitat use. We studied canyon wrens in Idaho's Lower Salmon River Gorge from 1996 to 1998. Our objectives were to (1) describe the pattern of canyon wren distribution by community type, (2) quantify macro- and microhabitat use and selection, and (3) test the hypothesis that temperature fluctuations in nest cavities differed from those in randomly selected cavities. Distribution of wrens was not random. We observed 65% of canyon wrens (of a sample of 1,622) in narrow, rocky canyons, which composed only 42% of the study area; 35% were observed in steeply sloping grasslands with occasional rock outcroppings. Wrens selected canyon habitats 69% more than expected based on availability. Macrohabitat was dominated by 76% more large rocks (>1 m diameter) and 71% less vegetation than expected based on availability. Large rock differentiated best between microhabitat used by wrens and available microhabitat. Temperature fluctuations in nest cavities were 98% less extreme than those recorded at randomly selected sites. Most canyon wren habitats were resistant to typical environmental changes and perturbations; therefore, we see little need for habitat management. Further study is warranted to determine impacts of recreational use near nesting and foraging areas.