eWestern Birds
The Quarterly Journal of Western Field Ornithologists
A Noninvasive Technique for Sampling Food Availability for Foliage-Gleaning Birds
Joseph J. Fontaine and Karie L. Decker
ABSTRACT: We describe a noninvasive modification to the technique of branch-clipping for sampling arthropods and evaluate its efficacy for studying food resources for a foliage-gleaning warbler breeding in the sky islands of southern Arizona. In the foliage-area method, arthropod abundance is measured on individual branches, and search area is controlled for by estimating surface area with a shadowed grid, analogous to canopy cover being estimated with a densiometer. Our technique enables repeated sampling of the same branch, which can limit sampling error and facilitates detailed studies of phenology across seasons and over multiple years. Overall it required less effort than traditional approaches, but because of the logistical challenges associated with sampling tree canopies, it is best suited for studies of species that forage relatively low to the ground. The foliage-area method does not alter the habitat, making it ideally suited for studies in protected areas, when foliage is limiting, or for work with food crops or endangered plant species..
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