Prey of the Loggerhead Shrike in West Texas

• In Event: Conservation Ecology Oral Session & Section Meeting

Abstract

While the ecological impacts of apex predators are well known, the trophic effect of secondary consumers (“mesopredators”) is less well known and more difficult to quantify. Loggerhead shrikes are small predatory birds that are common secondary consumers in open habitats throughout the United States. Loggerhead shrikes are generalist predators on arthropods and small vertebrates and important selective agents on these animals. We surveyed an active shrike larder (a barbed wire fence) in West Texas once per month during 2014-2017 to quantify the seasonal abundance and identity of shrike prey. We also studied prey turnover time weekly during 2017 to estimate the total number of prey impaled at this location. 1295 individual prey items were collected during 34 surveys. Shrikes preyed upon 15 orders of arthropods and 13 species of amphibians and reptiles, and several unidentified species of small mammals and birds. Incidence and diversity of impaled prey was highest during October-December. Orthopterans (mostly grasshoppers) were the most abundant impaled prey (average 18 found imapled per survey), followed by Coleopterans (average 14 found per survey) and lizards (average 6 per survey). Our estimates of predation rates suggest impaled prey turnover time at this larder is rapid, so that our monthly collections exemplify less than one week of predation on average by the local population of shrikes. In addition, shrikes often consume prey immediately and only impale a small subset of their prey. Therefore, the number of prey killed by shrikes is considerably higher than the total numbers reported here.

Authors

• Sean Graham, Sul Ross State University

• Morgan Seiler, Sul Ross State University

• Crystal Kelehear, Sul Ross State University