Winter diet, seed preferences and foraging behavior of Henslow\u27s Sparrows (Ammodramus henslowii) in southeastern Louisiana

Henslow\u27s Sparrow (Ammodramus henslowii) is a grassland bird whose population is declining throughout its range, mainly due to habitat loss. The Longleaf Pine forest ecosystems in which Henslow\u27s Sparrows spend their winters are reduced to 5% of their former range. The winter ecology of Henslow\u27s Sparrow remains understudied, especially regarding important aspects of diet and foraging behavior. To determine winter diet, I collected fecal samples from Henslow\u27s Sparrows during banding operations in southeastern Louisiana pine savannas from October 2003-March 2004 and October 2004-April 2005. I then analyzed the samples for presence of seeds and arthropod parts, identified them to the lowest classification possible, and then used both multivariate and univariate techniques to look for variations in diet due to a savannas burn history, month of year and their interaction. I also conducted multiple-offer and simple-offer seed preference experiments on captive Henslow\u27s Sparrows in December 2004 and February 2005 to test a variety of seed types found at differing abundances within the study sites. Commonly consumed seeds included Scleria spp., Rhynchospora spp., the category including Dichanthelium spp. and Panicum spp., and the combined category of Aristida spp., Schizachyrium spp. and Andropogon spp. Frequently consumed arthropods included Arachnids and insects from the orders Coleoptera, Hymenoptera, Hemiptera and Orthoptera. Diets varied significantly among months, most likely due to resource availability and timing of seed senescence. Results of seed preference experiments suggest that Henslow\u27s Sparrows preferred Dichanthelium angustifolium, Muhlenbergia expansa and Eupatorium leucolepis while they avoided Schizachyrium scoparium. Ctenium aromaticum and Panicum anceps appeared to be secondarily preferred food items