Assessing the impact of colour-ring codes on parameter estimates from Cormack–Jolly–Seber models: a test with the Yellow-legged Gull (Larus michahellis)

Abstract

The type of ring (i.e. its colour combination: the colour of the alphanumeric characters and the base colour of the ring) used in population dynamics studies could have an effect on parameters such as resighting probability (p); for instance, we might expect a lower p value when using rings with white characters than when using rings with dark characters. We performed an experiment using two types of colour rings (white or black characters on a dark base) in Yellow-legged Gulls in order to test our hypothesis. To do this, we used Cormack–Jolly–Seber (CJS) models incorporating variation in p among the birds. We obtained no evidence supporting an effect of type of ring on either survival or p.