The effect of rearing experience on subsequent behavioural traits in Hawaiian Geese Branta sandvicensis: Implications for the recovery programme

Abstract

The risk of the Nene Branta sandvicensis becoming extinct has been minimized by the release of over 2,000 captive-reared geese, but the population (now at 500) is yet to achieve a self-sustaining status. The majority of birds released have been reared in gosling-only groups, thus missing out on the opportunity to learn social and feeding skills from adults. In this paper we test the hypothesis that rearing experience affects the subsequent behavioural traits of Nene goslings. We raised 42 goslings under four conditions: a gosling group not exposed to adults, a gosling group exposed to adults from 16 days onward, three groups in view of “foster” adults for 14 days, and four groups reared continuously by parents. All birds were eventually released into an 8 ha pen where a flock of adult Nene roamed. The method by which Nene goslings were raised had a significant effect on dominance, flock integration, and vigilance. Parent-reared birds were dominant to and more vigilant than goslings raised without parents or goslings reared in sight of adults. Parent-reared birds also integrated into the adult flock sooner than other goslings. Growth rate and final body size were not affected by rearing regime (with or without parents or foster parents). In future, managers should provide goslings with as much “parental” experience as possible in order to equip them with appropriate skills to cope once released in the wild. © 1992, Birdlife International. All rights reserved.