Influence of Incubation Calls on Post-hatching Responses of Pheasant Chicks

Ring-necked Pheasant (Phasianus colchicus) chicks exposed to a hen incubation vocalization during the final week of incubation showed stronger attraction to feeding and caution calls than expected by chance when tested one, three and five days post-hatching. Control chicks incubated in silence did not differ from chance in response to the caution call. Largest differences between experimental and control chicks for positive responses to the caution call occurred at one and three days post-hatching. Differences for positive response to the feeding call were greatest at one and five days post-hatching. Correct pecking behavior in response to feeding calls was greater at all test ages in chicks exposed to incubation calls than in control chicks. However, when tested on the caution call, control chicks responded with correct hiding behavior more often than experimentals at one day of age. Correct behavior in response to the caution call greatly increased in experimental chicks at three days post-hatching but not in controls. By five days post-hatching, experimentals and controls were nearly equal. Calls by the incubating hen pheasant act to sensitize and predispose embryonic chicks for proper responses to calls that they will hear after hatching. Stages of post-hatching development and learning possibly have some modifying influence on the timing of responsiveness to post-hatching calls. Kuo (1921, 1932) was the first to suggest hat at least some features of apparently innate behavior of neonatal animals might be the result of experiences that occurred during late embryonic stages. Exposure of developing embryos to various sounds including self-auditory stimulation, sound stimulation by siblings and extra-egg sound sources has been shown to affect recognition of parent calls after hatching (Gottlieb 1965, 1971, 1974, 1975a, b, c, 1978) in domestic chickens (Gallus gallus var. domesticus), domestic Pekin ducks (Anas platyrhynchos var. domesticus) and Wood Ducks (Aix sponsa). Mallard (Anus platyrhynchos) ducklings also show post-hatching recognition of, and attraction to, calls heard during the late embryonic stage (Hess 1972, 1973). Bailey and Ralph (1975) found increased attraction for and movement toward sounds heard during late incubation in Ring-necked Pheasant chicks (Phasianus colchicus). Semi-precocious Laughing Gull (Larus atricillu) chicks respond to calls of the natural parents, but not to strange parents, if the chicks have had prior experience with the calls of their parents (Beer 1970, Impekoven 1976). Early post-hatching exposure of Ring-billed Gull (Larus delawarensis) chicks to feeding vocalizations of adults increases recognition of individual adults (Evans 1980). Perinatal exposure to parental calls in Common Murre (Uris aalge) chicks determines recognition of the parents and enhances preference for the parent-specific calls in choice tests (Tschanz 1968). However, in these studies, whether prenatal, perinatal or postnatal exposure to calls, preference and recognition was for the same sound heard during initial exposure and might be considered as associative learning (Bailey and Ralph 1975). Incubating Ring-necked Pheasant hens vocalize throughout most of the 23-day incubation period with a variety of low-frequency, low-intensity calls. Field observations and recording of incubating hen pheasants revealed an increase in some of these calls and a decrease in others as hatch approached. The call most frequently given by incubating hens during the final week of incubation can be described as a “mew” sound of low frequency, relatively long duration and modulated downwards (Fig. la). Pheasant chicks are brooded on the nest for 24 to 48 h before the hen leaves and vocalizes to the chicks, who then follow. The calls that the hen gave during incubation are replaced by other calls, which were never given during incubation. These post-hatching calls-a feeding or brood-gathering call (Fig. 1 b) and caution call (Fig. lc)-are obeyed correctly by the chicks the first time the hen gives them (Simmons 1975). Heinz and Gysel (1970) have documented the various adult pheasant calls including feeding and caution calls. Heinz (1973) found, in the laboratory, that day-old pheasant chicks were attracted equally to the feeding call (brood gathering call) and the caution calls. However,