THE PECKING RESPONSE OF YOUNG ARCTIC TERNS STERNA MACRURA AND THE ADAPTTVENESS OF THE “RELEASING MECHANISM”

• Published in: Ibis
• Main Authors: Quine, D. A., Cullen, J. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1964
• Subjects: Arctic; The Beak; Arctic tern
• Online Access: http://dx.doi.org/10.1111/j.1474-919x.1964.tb03693.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1474-919X.1964.tb03693.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1474-919X.1964.tb03693.x

Summary Experiments were made using models to analyse the stimuli evoking the pecking behaviour of young Arctic Terns, with comparative tests on Herring Gulls in one year. Some of the findings for the Arctic Tern may be summarized as follows. The chicks pecked at red, blue and silver more than at orange, yellow, green, black and white, and the response was increased by adding a contrasting spot to a beak. A plain red beak, the natural colour in the breeding season, was pecked less than one tipped with black, the colour in the winter. Chicks responded more to the beak models when a “fish” was attached (Fig. 1). Under natural conditions the chicks swallow their food, chiefly the sandeel Ammodytes , head first, and this is facilitated by the chicks pecking more at the head than the tail end of the fish. The stimuli by which head and tail are distinguished were found to be the pattern of the eye and tail‐fin rather than the shape of head and tail. The view that the selectiveness of the tern chicks is adapted specifically to the feeding situation is discussed critically, using the comparative results from the Herring Gull tests, and it is argued that while this is not the case for some of the stimuli effective in evoking the pecking (e.g. movement), whose adaptive significance concerns the general efficiency of the eye, it could well be responsible for some of the selectiveness found (e.g. high response to blue, low response to tail‐fin patterns). Comparison of the two species suggests that the Arctic Tern is specially adapted to respond to fish‐like objects attached to the beak. In the Herring Gull the ability to distinguish the head and tail of a fish appears to anticipate the time when the chick requires it.