The Development of Filial Behavior in Ducklings

Abstract

1. It has been shown previously that tendency of ducklings (Anas platyyhynchos) to approach a moving object upon first exposure declines within a few days after hatching. The reasons for this decline were investigated here. 2. The stability of body temperature in resting ducklings increased in the first 5 days after hatching, but during this time the difference in temperature stability between resting and rapidly walking birds was negligible. It is concluded that changes with age in the temperature stability of resting birds do not influence approach tendencies. 3. Large injections of androgen, but not estrogen, inhibited approach-responses of ducklings. A natural increase in circulating androgen might have similar effects. 4. Ducklings exposed to auditory stimulation resembling duck calls for as long as 2 1/2 days after hatching approached a moving model in a silent test no less than ducklings reared in auditory isolation. It is concluded that the vocalizations of other ducks do not inhibit the approach of ducklings to a visual stimulus. 5. Ducklings exposed to visual stimulation from a fluorescent bulb for two days after hatching were less likely to approach an intermittent light source of low contrast than birds reared in darkness. It is concluded that the inhibition depends in part on the brightness of stimulation. 6. Ducklings exposed to each other socially, but prevented from tactile contact, approached a moving model no less than birds reared in visual isolation. The finding of previous studies that unrestricted social contact inhibits approach-responses suggests that bodily contact between ducklings may contribute to the decline of initial approach-responses. 7. It is concluded that the sensitive period for imprinting ends as a result of both imprinting itself and an unspecific effect of photic stimulation.