Individual study: Hawaiian goose Branta sandvicensis releases failed to establish a self-supporting population in Hawaii, USA
Black J.M., Marshall A.P., Gilburn A., Hoshide H., Medeiros J., Hodges C.N. & Katahira L. (1997) Survival, Movements, and Breeding of Released Hawaiian Geese: An Assessment of the Reintroduction Program. The Journal of Wildlife Management, 61, 1161-1173
Hawaiian geese (nene) Branta sandvicensis were reduced to 30 wild and 13 captive individuals in 1949. A large-scale captive-breeding and reintroduction programme was begun. This study reports on the programme’s impact.
Large numbers of Hawaiian geese were bred in captivity and released at one low to mid-elevation site and four high-elevation sites on Hawaii and one high-elevation site on Maui.
All geese were kept in enclosures following release and were either released before fledging, or had their wings clipped to prevent them leaving the enclosure too quickly.
Goose survival and reproduction were monitored after release and their movements recorded using individual colour rings.
Since 1949, 2,150 birds were released but this did not result in a self-sustaining wild population.
Estimated mortality rates ranged from 0-87% annually, although were generally low until droughts in 1973-86, when 1,200 released geese died. Mortality rates were lower in the lowest-altitude release site (at <1,300 m a.s.l.), with only three years between 1976 and 1983 having mortality rates over 15%. In contrast, the few geese released in uplands that survived the droughts did so by migrating away from their release site.
Over the study period there were 515 nests recorded, with 37% raising at least one gosling. Overall there were 473 goslings raised (0.92 goslings/nest), with the highest rates in lowland sites.
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