Studies on the population of barnacle geese Branta leucopsis wintering on the Inishkea Islands, Co. Mayo. I. Population dynamics 1961-1983.

The Greenland breeding population of barnacle geese wintering on the Inishkea Islands has remained remarkably stable during the period 1961-1983 against a background of overall population growth of 4.2% per annum in the Greenland stock. The carrying capacity of the islands, under the present land use regime, has been reached for some time. The Inishkea wintering population is characterised by constant low productivity and a low rate of loss of geese. Islay (Scotland) wintering geese are twice as productive as Inishkea birds and the percentage of successful breeding adults is twice as high. The Islay population shows a slightly higher 'loss' or assumed mortality. Against this background, numbers on Islay have increased by 6.7% per annum, the fastest rate within the wintering range. However, changes are now occurring (declining productivity and increasing mortality) which may lead to a long term decline in numbers on Islay. On Inishkea the family parties maintain their integrity over the winter period and show no evidence of break up. The proportion of first winter birds is variable throughout the winter and may show significant increase or decrease between October and April. -from Authors