Second-brooding in semi-captive Barnacle Geese

Abstract

Five different pairs of Barnacle Geese Branta leucopsis from a flock of 200 free-flying birds at the Wildfowl Trust in southern England each produced a second clutch of eggs while rearing goslings from the first clutch. 'Second-brooding' occurred in five of the six years 1980 to 1985. Only two of the pairs were closely related and one of the males originated from an egg taken from the wild. In two cases, the second clutch was incubated to hatching and goslings from the two broods reared as one family. This phenomenon, hitherto unrecorded in geese, could never occur in arctic-breeding geese in the wild because of the shortness of the season and limited food supply. It is suggested that a superabundant food supply enables these geese quickly to regain breeding condition following the hatching of the first clutch. This evidently over-rides the suppressing effects of parental hormones. An unnatural photoperiodic cycle at southerly latitides may also contribute by causing a failure of the geese to become photo-refractory after completing one nesting cycle.