WINTER TERRITORIES AND NIGHT ROOSTS OF NORTHERN SHRIKES IN IDAHO

To study the winter ecology of Northern Shrikes in southwest Idaho, I observed the activities of six color-banded and six radio-tagged shrik es over the winters of 1988-1989 and 1989-1990. These shrikes occupied winter territories that averaged 216 ha in size (minimum convex polyg on method). Over one-half of the activity of each shrike was confined to a core area of approximately 50 ha. Five of nine individual Norther n Shrikes perched in or hunted within mesic areas significantly more t han expected and four of the nine utilized grasslands significantly le ss than expected. Linear habitats such as riparian corridors and rimro ck outcroppings appeared to be important to wintering shrikes since th e former provided night roost habitat whereas the latter provided warm and productive areas for prey populations. I located 10 night roosts of Northern Shrikes. All were in deciduous shrubs with many small stem s. Shrikes may depend upon these roosts for thermal protection and esc ape from predators.