Food selection by chicks: Effects of colour,density and frequency of food types

Previous studies have shown that birds, including 3-day old chicks, show frequency-dependent selection when feeding on a food population made up of two types. Two experiments using 5-day old chicks are described here. In one, foods of three colours were presented in their three pairwise combinations, at five different relative frequencies. It was found that measures of selection were transitive: that is, selection of red versus yellow could be predicted from selection for red versus green and for green versus yellow. Selection was not frequency-dependent. In the second experiment, total food density, as well as relative frequency, was varied. Selection was density-dependent, being strongest at the middle one of the three densities. It was also irregularly frequency-dependent, being weaker at one (inter-mediate) frequency than at the other four, among which there was little variation.