LOGGERHEAD SHRIKE PREDATION ON DUNE-DWELLING LIZARDS AND NESTING SUCCESS IN SOUTHEASTERN NEW MEXICO

Abstract

Predation of dunes sagebrush lizards (Sceloporus arenicolus) by loggerhead shrikes (Lanius ludovicianus) is not well-understood. The goal of this project was to determine if the frequency of dunes sagebrush lizards as prey by loggerhead shrikes was greater in areas that were fragmented by oil and gas development compared with unfragmented habitat. We deployed motion-activated game cameras at shrike nests to determine what prey was being fed at the nests, we quantified the amount of time shrikes spent hunting from power lines or other anthropogenic perches, and we collected shrike pellets to look for the presence of dunes sagebrush lizard scales. Camera data results indicate that lizards make up approximately 10% of the prey items that loggerhead shrikes take to the nest. The difference in overall lizard captures between fragmented and unfragmented habitat was not statistically significant. Power-line survey results indicate that loggerhead shrikes hunt from anthropogenic perches approximately 50% of the time. The analysis of camera-trap images allowed us to identify two individual dunes sagebrush lizards, each from a nest in fragmented habitat, and the pellet analysis documented one instance in unfragmented habitat. An opportunistic finding in a shrike food larder in unfragmented habitat documented six additional dunes sagebrush lizards that were impaled on barbed wire. These results indicate that loggerhead shrikes do sometimes predate dunes sagebrush lizards, although samples sizes were too small to determine predation rates between the habitat types.