Mallard with Blue/grey bill (1 Viewer)

Hi,

Couple of weeks ago I was scanning a flock of Mallard on a pond and came across two with blue-grey bills instead of the usual dull yellow. The bill colour was the only unusual thing about those birds, they were close enough to see well and the light was good too. Anyone seen this before?

Cw

Did your bird look like the one attached?

I may be wrong but I assumed birds with a duller bill were immature males.

Yip, that's him alright. Yea, they could be immature males but I checked out my Collins guide at the time and didn't see any mention of blue bills.
Nice pic.

Cw

Here's a C&P from BWPi about bare part colouration in mallard

Adult Male
Iris dark brown. Bill olive-green to bright yellow, occasionally pale blue or green-blue (dullest in eclipse), culmen and tip dull black. Foot orange-red.

Adult Female
Iris and foot like adult ♂. Bill dull yellow-orange to olive-brown, culmen, upper sides, and tip dark horn; some dark dots along edge of upper mandible.

Downy Young
Iris brown. Bill flesh, spotted black; nail pink-white. Foot dark olive-grey.

Juvenile
Iris dark brown. Bill red-horn, becoming darker when older; in ♀ sides paler, often small dots along edge of upper mandible. Foot dull flesh or yellow to yellow-orange, webs darker. (Bauer and Glutz von Blotzheim 1968; Lebret 1961; Schiøler 1925; Witherby et al. 1939; RMNH, ZMA.)

Cheers Keith.