Effects of supplementary feeding on provisioning and growth rates of Atlantic Puffin Fratercula arctica chicks in North Norway

After many years of a gradual change in chick diet and a supposed deterioration in feeding conditions, chicks of Atlantic Puffins Fratercula arctica were fed 50 g supplementary food per day (capelin Mallotus villosus) to test if they grew faster than control chicks, thus indicating that conditions really were suboptimal. Growth rates were, however, approximately the same as for control chicks through a near halving of provisioning rate by the experimental parents. This suggests that feeding conditions, despite a large change in diet composition, were still adequate for normal breeding.