Foraging Rates of Starlings in Two Habitats

FIGURE5. Order of selection of red and yellow peanuts in the evening.One pile of 20 red (black dots) and 20 yellow (white dots) peanuts was set out. ber of tests by shaking of red shells appeared to decrease with each session, as well as the number of initial selections being red.Following these five learning sessions, we tested the birds for their initial color selection from only five green and five red peanuts.The pile of peanuts was restored to its original composition after every two selections.The purpose of this test was to determine how long the birds would continue to select green over red when provided with no differential reward for green.Within 48 h after the last learning session, the birds reverted to their natural color preference (Table 1).Our findings support those of earlier studies of avian color preference in demonstrating that color serves as an important discriminator stimulus in the FORAGING RATES OF STARLINGS IN TWO HABITATSC. BARBARA BROWNSMITH Williamson and Gray (Condor 77:84-89, 1975) found that Starlings (Sturnus vulgaris) forage in at least four types of habitat.Starlings thus seemed a good species with which to study foraging behavior selection of food (Grant, Am.Nat.100:85, 1966; Collias and Collias, Condor 70:273, 1968; Miller and Miller, Condor ' 73:309, 1971).By not varying the position or quality of the food supply, we found that Steller' s Jays exhibit a natural order of color preference of red, yellow, blue and green; this order was the same regardless of how many different colors of peanuts were set out.This preference scheme becomes more important when competition for food is increased.As might be expected for an omnivorous bird with opportunistic feeding habits (Hardy, Condor 76: 102, 1974; Alcock, Behaviour 46: 174, 1973), we found that the jays could readily be trained to adopt an inverted color preference scheme in response to a short-term negative stimulus.Furthermore, they tended to persist in using this inverted scheme after termination of the negative stimulus.Because we did not mark individual birds, we do not know the constancy of the members of the population under observation.Demonstration of short-term learning by the birds, however, indicates that for the most part we saw the same individuals on each visit.This particular color preference scheme may, of course, pertain only during the summer season within the locale of this study.Our observations demonstrate, nevertheless, that the jays use this scheme as one of their primary factors in selecting food.They depend upon it even more when competition is keener and abandon it only on a short-term basis if there is a differential reward for doing so.Our findings thus indicate that Steller' s Jays, either innately or as a result of long-term experience, are more likely to take advantage of a potential food source if it is red or yellow rather than blue or green.If, however, they encounter a desirable food with a color low on their natural color preference scheme, they quickly learn to associate this color with the particular food and use it as one of the primary visual cues in their search for this food supply.