Meeting Abstract
30.1 Monday, Jan. 5 Latitudinal Variation in Winter Immune Function in a Differential Migrant O’NEAL, DM*; SWANGER, L; KETTERSON, ED; Indiana University; Indiana University; Indiana University daoneal@indiana.edu
Sex differences in migratory behavior (differential migration) can give rise to sexual segregation during the non-breeding season. The dark-eyed junco (Junco hyemalis) is one such differential migrant with females moving farther south in the winter than males. Northern latitudes are traditionally characterized by extreme temperature drops and unpredictable food resources due to snow cover, and both these conditions may increase metabolic needs and the frequency of potentially stressful competitive interactions. Additionally, disease prevalence is generally lower in northern locations, as colder temperatures restrict the growth, development, and persistence of parasites, mites, and vectors carrying disease. Combined, these factors suggest reduced immune function at northern latitudes. Recent winter warming, however, has reduced prolonged snow cover, and possibly increased available winter food resources and disease prevalence, possibly affecting latitudinal variation in immune function. In this study we evaluated innate immune function in free-living juncos during winter across a latitudinal gradient including Michigan, Indiana, and Mississippi. We asked whether immune function was correlated with climate factors associated with winter latitudes including average winter temperature, average snowfall, lowest temperature recorded, and maximum winter snow depth. Birds were captured at baited mist nets and potter traps between December 1st (the cessation of autumn migration) and March 1st (the start of spring migration). Upon capture birds were aged and sexed using morphological measures and a small blood sample was collected for innate immune measures. Preliminary results indicate latitudinal differences in immune function but the role of climate in these differences appears to be more complex than anticipated.
