ROOSENBERG, A.S.*; TIELEMAN, B.I. ; WILLIAMS, J.B. ; KLASING, K.C. ; Ohio State University, Columbus; University of Missouri, St. Louis; Ohio State University, Columbus; University of California, Davis: Seasonal trends in immune function of tropical house wrens

In wild avian populations, relatively little is known about variation in immunological capabilities. We studied the constitutive innate immunity within a species, among individuals of the tropical house wren, Troglodytes aedon. Constitutive innate immunity provides a first line of defense against invading pathogens, including components of both humoral and cellular immunity. We used an assay to quantify the bactericidal capacity of whole blood, providing an integrative measure of constitutive innate immunity. This assay allows a single blood sample to be taken, allowing it to be easily used in wild populations. Data was collected from residential areas of Gamboa, Panama, between April and July of 2004 and 2005. Blood was collected from both sexes of house wrens during different distinct stages of breeding. Bactericidal activity of the whole blood was measured using one to three various microorganisms: E. coli, S. aureus, and C. albicans. Phagocytosis of E. coli and blood smears were also analyzed to provide further information about the state of individual immunity. We found that the bactericidal capacity of whole blood varied consistently among individuals but that this variation was not correlated with factors such as sex, body mass or current stage in the breeding cycle. However, bactericidal killing of E. coli was positively correlated with calendar date. Among individuals of the house wren, killing ability of whole blood increased as the year progressed from the dry season into the wet season.