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The life cycle of the Upland Goose Chloëphaga picta in the Falkland Islands
Author(s) -
Summers Ronald W.
Publication year - 1983
Publication title -
ibis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 80
eISSN - 1474-919X
pISSN - 0019-1019
DOI - 10.1111/j.1474-919x.1983.tb03146.x
Subject(s) - fledge , brood , flock , breed , biology , goose , nest (protein structural motif) , population , avian clutch size , zoology , moulting , hatching , ecology , geography , reproduction , larva , demography , biochemistry , sociology
Upland Geese Chloëphaga picta were studied between 1977 and 1980, primarily around Darwin, East Falkland, in order to describe their breeding biology, moulting and adult survival. The population of breeding birds in a valley reached a peak from mid‐September to late November when nesting took place. The average territory length was 240 m in five valleys. Breeding adults generally returned to breed in the same territory each year and with the same mate. Nests were on the ground, usually amongst whitegrass Cortaderiapilosa. The mean clutch size was 6‐1, brood size was 5‐1 and fledged family 3–9. Incubation took 30 days and the fledgling period was about 70 days. Most broods were raised in the nesting territory. Growth of goslings is described. The breeding success between laying and fledging was 0–34 (in 1977) and 0–29(in 1978), giving an annual production of 21 and 1–8 young per breeding pair. Fledglings remained in family parties through the autumn and winter and were evicted by their parents in early spring. Some siblings stayed together for short periods and then joined other non‐breeders. Females started pairing at ten months of age and most were paired at 17–18 months. Some bred for the first time at 23 months. Males started pairing at about 20 months of age. Flightless moult (shedding) took place at ponds or in sheltered inlets of the sea, in flocks of up to several hundred birds. Flightless birds were found between 14 November and 11 February, though 50% were flightless between 26 November and 2 January. Individuals were flightless for 36 days. First‐year birds were more synchronized in shedding than adults. The percentage of first‐year males (in the male component) varied from 16‐5 to 45‐9% in shedding flocks, and significantly more males were present in some flocks. The flocks were composed of first‐year and second‐year birds too young to breed and failed breeders. The percentage of a shedding population which returned to the same site in successive years was 25‐3 and 15‐1% at two localities. The moult of other feather tracts is described. The annual survival rate of breeding adults was 82%. A model of the population dynamics is presented. The current level of culling to control the goose population is less than the number which must die each year to maintain a stable population.