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Wren-Tit Attempts Copulation with Begging Fledgling

Charles G. Sibley
Publication Information
2 (March-April)
From Field and Study

Wren-tit Attempts Copulation with Begging Fledgling.-The resemblance between the posture of a begging passerine fledgling and that of an adult female during courtship, has often been noted. Both the begging fledgling and the adult female assume a crouching position accompanied by a fluttering of the wings. The function of the posture in the fledgling is to release the feeding response of the adults. In the female the posture is usually indicative of a readiness to copulate. In many species the male of a pair feeds the crouched, fluttering female. This act of “courtship feeding” has been discussed by Lack (Auk, 57, 1940:169-178) and by Armstrong (Bird Display and Behaviour, 1947: 43-50). Courtship feeding may precede or accompany copulation.

On June 5, 1951, an adult Wren-tit (Chamaea fasciata) accompanied by two begging fledglings came to a feeding tray less than 10 feet from my point of observation. The adult fed each fledgling twice, then mounted one of the crouching, fluttering fledglings in copulatory position. It remained on the fledgling’s back for approximately 2 seconds before hopping off to resume feeding the youngsters.

This observation lends support to the belief that the pre-copulatory display of the female in many passerines is truly similar to the begging display of the fledgling. Both postures seem capable of releasing copulatory behavior in the Wren-tit.-CHARLES G. SIBLEY, San Jose State College, San Jose, California, January 15,1952. 

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