VARIATION IN LOGGERHEAD SHRIKE NEST COMPOSITION BETWEEN 2 SHRUB SPECIES IN SOUTHWEST IDAHO

Loggerhead Shrike (Lanius ludovicianus) nests constructed in sagebrush (Artemisia tridentata) and greasewood (Sarcobatus vermiculatus) shrub s contained different proportions (by weight) of nest material of diff erent thicknesses. Nests constructed in dense greasewood shrubs contai ned fewer medium and large sticks, typically used in construction of t he nest substructure, than nests built in relatively open sagebrush. I n contrast, there was no difference in quantity of lining-fibers, twig s, and small sticks used in nests constructed in these shrubs. These d ifferences can be attributed to different nest-stabilization requireme nts imposed on breeding shrikes by structurally dissimilar nesting sub strates and imply plasticity in shrike nest-building behavior.