GCSpyder’s study of the Oriental Pied Hornbill (Anthracoceros albirostris) flying over Singapore’s Changi Village shows the wear and tear of the tail feather as well as the moulting of the flight feathers.
An undamaged feather has the barbs firmly attached one to another, resulting in a smooth, continuous surface of the vanes. Many of the tail feathers in the image show damage through wear and tear, resulting in gaps in the vanes.
Worn out feathers are replaced continuously, as seen in the flight feathers. The gaps around where the primary flight feathers meet with the secondary flight feathers in both wings are points of moulting. Here, the old feathers have been discarded and new ones are actively growing. This is symmetrical moulting, to provide balance while in flight. Asymmetrical moulting, where moulting occurs in one wing only, seen in the Brahminy Kite (Haliastur indus intermedius) that earlier had a fight and probably lost its feathers through fright moult, is unusual.
As flight feathers play important roles in flying, they are usually replaced one or two at a time.
This post is a cooperative effort between NaturePixels.org and BESG to bring the study of bird behaviour through photography to a wider audience.