Timing and extent of primary moult in breeding Black-legged Kittiwakes Rissa tridactyla at different colonies in the north-east Atlantic

Timing of moult of the inner primaries by breeding Black-legged Kittiwakes is very similar among colonies ranging from southern England to northern Norway, but can be much later at very high-latitude colonies, such as at Svalbard, where breeding is delayed by the late spring thaw. Breeding adult Black-legged Kittiwakes almost all replaced the first and second (innermost) primary feathers on their wings while breeding.