Structural and mechanical differences between original and replaced feathers in Blackcaps Sylvia atricapilla

Abstract

Many bird species are able to replace accidentally lost feathers out of the normal moulting periods, but whether such replaced feathers are able to restore the original mechanical properties of the plumage has not been evaluated before. In this study we analysed the structure and mechanical behaviour of the original and replaced feathers of 12 blackcaps Sylvia atricapilla. Replaced feathers showed wider rachis and greater density of barbs, but were lighter, shorter and less stiff than original feathers. These results suggest that replaced feathers are not able to fully restore the original functionality of feathers.