Effects of Food Density on the Behavior and Distribution of Nonbreeding American Flamingos in Yucatan, Mexico

We sampled potential food items of American Flamingos (Phoenicopterus ruber ruber) in the Celestún Estuary, Yucatân, Mexico, from October 1992 to January 1993, to explore the influence of food density and distribution on flamingo behavior in relation to the ideal free distribution model. Food items were found in the substrate and vegetation and were dominated by four groups: gastropods (40%), muskgrass bulbils (26%), crustaceans (11%), and chironomids (10%). Overall, food was patchily distributed and food abundance decreased over time. Flocks initially concentrated in areas where food was most abundant, but appeared to deplete food resources in these areas after which they dispersed throughout the Celestún Estuary. Time spent feeding also was lower in the first two time blocks (x¯ = 26%) when food was most abundant, and then increased and remained constant (56%) in the remaining five time blocks. Mean flock size was 457, and did not differ among locations through time, except in the last time block when flocks tended to be larger (x¯ = 821). We concluded that the distribution of flamingo flocks was consistent with the ideal free model based on food density and distribution, but that major perturbations (storms) can dramatically affect flamingo distribution. However, relative payoff for individuals within flocks has yet to be determined.