with comments on aging criteria The molt cycle of the Arctic Tern

Molt-data from museum specimens of Arctic Terns (Sterna paradisaea) were analyzed and considered in relation to other life-history aspects. Differences in shape and color of outer tail feathers were reliable indicators of age class, allowing second-year birds to be distinguished from third-year birds, and second-and third-year birds from after-third-year birds. No differences in molt pattern were found between subadult age classes, or between subadult and adult age classes. The duration of primary molt was estimated at 99 d for adults and 221 d for subadults. This difference in time allotted to molt probably results from constraints imposed on adults by migration and breeding. Adults replace all their flight feathers on the wintering grounds, whereas subadults often complete this molt in tropical latitudes where they summer. Arctic Terns appear to exhibit the second inner primary molt featured by most other Sterna species.

The molt cycle of the Arctic Tern, with comments on aging criteria Academic Article