The weights and wing lengths of fledgling Atlantic Puffins Fratercula arctica on the island of Sule Skerry, Scotland were recorded in eight seasons between 1982 and 2005. Chicks in 2005 were notably underweight compared to previous years. Measurements of 38 chicks over a period of 21 days showed that chicks grew very slowly and that fledging success was low. These findings and the records of pipefish (Sygnathidae) in the diet, suggest that conditions were unusually poor for Atlantic Puffins at Sule Skerry in 2005.

The offshore island of Sule Skerry, at 59o05’N 04o24’W, lies 72 km west of Mainland Orkney and a similar distance north of Tongue, Sutherland, Scotland. Half of its 14 ha comprises a peaty plateau at about 13 m above sea level on which grows extensive Sea Mayweed Tripleurospermum maritimum. Rocky areas and cliffs surround the plateau. It is a large seabird colony, and the Seabird 2000 census estimated the population of Atlantic Puffins Fratercula arctica there at 59,500 apparently occupied burrows, making it the second largest colony in Britain and Ireland at the time (Harris & Wanless 2004). The Sule Skerry Ringing Group has made 21 visits to the island since 1975, primarily to ring a sample of adult Atlantic Puffins (hereafter ‘Puffins’) and chicks, to monitor breeding numbers and adult survival and to monitor the condition of fledglings. Whilst visits in most years were for one or two weeks, in 2005 we were present for four weeks. Here we report on measurements of fledging Puffins over a 23-year period and chick development and fledging success in 2005.

Many individuals contributed to ringing activity on Sule Skerry over the years. Adrian Blackburn and Dave Budworth led most expeditions, and without their enthusiasm and drive much of these data would not of have been collected. Kevan Brett, Alex Lewis, Tim Naylor, Dave Parsons and Jackie Savery helped with the fieldwork in 2005. Jez Blackburn encouraged writing this paper from its inception, and Mike Harris and Stuart Newson gave invaluable assistance and advice on its preparation. Finally, we thank Tycho Anker-Nilssen and Matt Parsons for their comments as referees.

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