Sex and Age Differences in Site Fidelity, Food Resource Tracking, and Body Condition of Wintering Kirtland's Warblers (Setophaga kirtlandii) in the Bahamas. Ornithological Monographs No. 80. Distribution of nonbreeding migrant birds in relation to variation in food availability has been hypothesized to result from the interaction of dominance hierarchies and variable movement responses, which together may have sex- and age-specific consequences.