Biology and survival of the immature Puffin Fratercula arctica

The biology and survival of Puffins were studied in northeast Scotland. Puffins usually bred first when aged four or five years but returned for several seasons prior to this. Young birds were probably prevented from returning earlier in the season because they moult their primaries in the spring and early summer. As they got older, they came to the colony earlier in the year, displayed and tried to get a burrow. Younger immatures may summer in specific areas away from the colonies.
Many immatures visited colonies other than where they were hatched. This was particularly marked in July of their third year. Up to 23% of Puffins of both sexes permanently emigrated and it is suggested that such behaviour is widespread among auks.
About 60 % of fledglings returned to the natal colonies and 30% of fledglings appeared to reach breeding age (although the true figure will be higher as this does not include birds which emigrated). Adult survival was c. 96% per annum. The population could theoretically increase by c. 7% but the observed rate of increase was c. 9% per annum.