Prey Choice by Three Insectivorous Grassland Birds: Reevaluating Opportunism

Abstract

Assemblages of breeding grassland birds have typically been considered dietary opportunists. We studied prey selection by an assemblage of three breeding insectivores grasshopper sparrows, lark sparrows, and western meadowlarks ― in the Sandhills grasslands of Nebraska, USA and we contrast three foraging models with a null model of opportunism. Handling times and %-chitin varied among prey taxa. The profitability (grams of non-chitin intake/handling time) of acridids, a major part of the diet of all three birds, declined with body size of grasshoppers. We measured Selectivities by comparing arthropods recovered from avian guts with those recovered from sweep sampling. Birds preferred some prey taxa (e.g., acridids, tettigoniids, small Coleoptera) over others (e.g., Homoptera, Hymenoptera, spiders)