We've had several photos sent to us recently of red kites looking "worse for wear"!
Red kites moult a small number of their feathers on an annual basis, with non-breeding birds starting to moult earliest in the year (even as early as April). Parents tend to start moulting once their young have fledged in June / July.
Moulting is an energy-sapping process, it taking individual feathers 8 to 10 weeks to grow back to full size.
Many times you will spot that the gaps in the wing feathers are symmetrical (same on both sides), this is a natural occurrence helping the birds maintain their flying abilities. In general feathers will be moulted in the same pattern / order on each wing during each moult season, with moulting normally having concluded by November.
Our red kites do not migrate over large distances, though you will find them congregating in 'winter roosts'. As with many birds moulting is unusual during winter months as the birds are conserving their energy. If you see a bird with a missing feather at this time of the year it may well have been damaged by flying into something!
A section taken from © Sam Reynolds photo clearly shows at least 3 areas of regrowth on the right wing.
A great image from © Martin Roper showing asymetrical missing primary feathers near the end of the wing and regrowing secondaries (as seen) hidden from view nearer the body. We can clearly see a regrowing tail feather (retrices).
The image above from © Terence Porter, which featured in a previous News story, shows the white on primary feathers that is normally covered by the last (missing) primary feather.
And a final image from © Leon Kirkbride which appears to show a red kite with a damaged wing feather
There has been little research in to the annual moult of the red kites, but for those who would like to learn more about raptors and their moult we can suggest reading https://bioone.org/journals/ardeola/volume-65/issue-2/arla.65.2.2018.rp1/Moult-in-Birds-of-Prey--A-Review-of-Current/10.13157/arla.65.2.2018.rp1.full