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The Ontogeny of Impaling Behaviour in the Loggerhead Shrike, Lanius Ludovicianus L

1972; Brill; Volume: 42; Issue: 3-4 Linguagem: Inglês

10.1163/156853972x00284

1568-539X

Susan M. Smith,

Animal Nutrition and Physiology

Abstract 1 . The ontogeny of impaling (including wedging) behaviour by Loggerhead Shrikes was studied both in wild and in captive birds. 2. The earliest elements of impaling: "dabbing" and "dragging" behaviour, are described. 3. Field work was done in central Washington state; most of the data were obtained from two broods totalling 13 birds. Laboratory work was done on more than 60 hand-reared birds. 4. There did not appear to be any attempt by the parents to demonstrate impaling to either nestlings or fledglings. The young normally did not observe adults impaling food until they were past the age at which they start impaling by themselves. 5. The ontogeny of impaling under natural conditions was found to be essentially Identical to that of hand-reared birds that had been raised in cages containing natural branches. 6. The earliest dragging behaviour by both captive and wild birds was done as soon as the food was obtained, whether or not the bird was within reach of a thorn or fork. 7. The motor patterns of impaling (dragging behaviour) appeared in every young shrike by the age of 26 days. However, a period of trial-and-error behaviour was apparently necessary before these motions were directed towards a suitable place (i.e., thorn or fork). 8. Observational learning is not involved; birds that had been reared in the absence of any impaling device until they were at least 75 days old failed to use thorn branches when provided, regardless of whether or not they had had the opportunity to observe older birds impaling and wedging in an adjacent cage. 9. It is, therefore, concluded that personal experience with impaling devices is necessary for the appearance of the orientation component of impaling in Loggerhead Shrikes. Furthermore, this experience must occur within a "critical period" whose boundaries are roughly 20 to 70 days after hatching. 10. Hence, in this species, the orientation component of impaling is apparently normally learned by a process similar to imprinting.