The Post-Fledging Mortality of the Kittiwake

I. The inscriptions on rings used on the Kittiwake (Risa tridactyla) become illegible after 2 years.In addition, the rings lose nearly so per cent. of their initial weight each year.2. The annual adult mortality of the Kittiwake has been estimated as 12.4 per cent.± 2.2 per cent., based on the return of colour-ringed breeding birds to the North Shields colony, and as 7 per cent, from ringed adult birds at the Farne Islands.3. The mortality in the first year of life is 21 per cent.4. It has been deduced that most female Kittiwakes breed for the first time when 3 or 4 years old.