With a gazillion Mallards around the area, and each one of them moulting twice a year, one might expect to see them undergo this loss and regrowth of feathers with considerable frequency. Yet, I cannot recall having seen a Mallard in the process of moulting prior to Thursday.
When the female Mallard moults, she replaces her worn feathers with new ones having the same pattern. The transition is inconspicuous.
The male, however, switches between his breeding plumage and his eclipse plumage (during which time, he looks like a female). It is a big shift and during the transition, he should look distinctly anomalous.
So, why is this odd duck rarely seen?
Answer: He hides.
When a male Mallard moults, he loses all of his flight feathers simultaneously. His flightless state leaves him particularly vulnerable to predators. So just prior to moulting, he goes into seclusion, often hiding in a marsh. He is loath to reappear until in his breeding finery.
The odd-looking head and neck of Thursday’s male Mallard (foreground) reveals him to be only part way through the moult into breeding plumage. The colourful water results from the reflection of the fall foliage beyond them.