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Résumé :
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Barnacle geese wintering in Ireland and Scotland comprise the population breeding in east Greenland. This has increased from 11,800 to 23,970 between 1957 and 1973. However, numbers wintering in Ireland have remained stable at approximately 4,400. Differential breeding success in Greenland of Scottish and Irish birds may account for this difference. Ringing recoveries suggest that these have different breeding grounds. A thirteen-year study on the Inishkea Islands, Co. Mayo, which hold over 50% of the Irish birds has revealed a population fluctuating between 1,530 and 2,800 geese, with mean rates of recruitment and loss at 7.8% and 8.3% per annum. Overall, the mean brood size is 1.91 and the proportion of first winter birds 6.5%. There are significant positive correlations between mean brood size and both number and percentage of first winter birds; also between temperature on the wintering ground and mean brood size the following summer. It is suggested that availability of wintering grounds and temperature, through its effect on production of winter food, may be critical factors controlling breeding success in the Irish population. Sociological factors impinging on the population are considered, and it is concluded that barnacle geese should remain protected.
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