The Wildfowl Trust's second expedition to central Iceland, 1953

Abstract

Accurate measurements of the population of the Pink-footed Goose Anser brachyrhynchus by the marking and sampling method required ringing of these geese on a much larger scale than had previously been achieved. The success of the Trust's 1951 expedition to the Pinkfoot breeding-colony in bjrsrver, near the Hofsjkull icecap, suggested that techniques of capture then discovered might be very successful if developed and used throughout the period of about four weeks when the adult geese are flightless through moult and the young have not yet grown their wings. A party of eight, including three Icelanders, spent 29 days in this oasis of vegetation in the central highlands. 4144 adult geese and 4861 goslings were caught. 260 of the adults carried rings put on in previous years and marking methods are described in some detail. The size of the breeding colony in mid-July 1953 is estimated from local recapture data at 8200 adults and 10,200 goslings. Recaptures provide evidence that comparatively few one-year-old geese were captured, and that two-year-olds were present in numbers and distributed throughout the colony, rather than assembled in non-breeding flocks, but it is considered unlikely that two-year-olds breed successfully. The numbers of predators present in the area in 1953 was smaller than in 1951. Attempts to measure gosling losses are described. None of the methods used is very precise, but it appears that in both 1953 and 1951 the losses between hatching and entry into the measurable British population in mid-October amounted to about three-fifths of the goslings hatched. The casualties occur mainly in the first two or three weeks of life and immediately on arrival in Britain (in late September and the first week of October). Losses of this magnitude are consistent with the estimated replacement rate necessary to maintain the species at its present level of numbers. The length of the flightless period is thought to be rather shorter than was previously believed--about 25 days. A number of abnormal geese which were caught are described. Examination of some birds for evidence of fungal respiratory disease was negative. Three new species of birds were added to the list of 32 seen in the area in 1951, and 44 new species of plants to the list of 108 then found. A collection of plants was preserved for the British Museum, (Natural History).