Seed Selection By Pigeons

The food preferences of 59 captive Pigeons Columbia livia were tested in a series of experiments in which each bird was given a 25 g. seed mixture. This consisted of 5 g. each of Maize, Millet, Grain (Wheat, Oats and Barley), and two varieties of Field Pea (Big Peas and Small Peas). There was a wide range of individual variation. Most birds preferred Peas, and took little Maize; however, others actually preferred minority seeds such as Maize. These individual preferences were stable over short periods, though there were gradual, long-term changes in birds tested repeatedly over a period of four months. There were also individual differences in feeding technique, though these could not be correlated with the differences in seed preference. The origins of these individual variations are discussed. It was not possible to relate them to individual differences in bill size, nor to the proportions of the seeds in the birds' normal feed. When the total quantity of the experimental seed mixture was increased from 25 g. to 50 g., the birds increased their total intake while keeping constant the proportions of the different seeds in it. Since the seeds differ in nutritional composition, it is suggested that the birds were maintaining a nutritionally balanced diet. It is possible that the variations in seed preference may reflect individual differences in metabolism. Individual birds also maintained a constant ratio of Big Peas to Small Peas in their seed intake, even though these differ little, if at all, in nutritional content. It is suggested that such apparently arbitrary food choices might increase the efficiency of the birds' food-finding tactics. Some ecological implications are briefly outlined. If feeding is controlled by the quality as well as the quantity of available food, this could influence the extent to which the birds exploit their environment, and the degree to which their numbers are limited by the food supply.