Okay, continuing the previous discussion....the bill on this. bird lacks the grays of an adult male Northern Pintail, and the face and neck pattern are somewhat muted. The barring on the sides isn't anything like what is typically seen, and the tertials aren't right. The long tail isn't quite as long as it should be, and the color of the undertail isn't black. This photo was taken in January, so we aren't dealing with some weird eclipse plumage.

Pintails WILL hybridize occasionally, but what combo could this possibly be?

The reality is that this isn't a drake at all, but instead, is an old hen, one that is producing less oestrogen than normal. In ducks, oestrogen suppresses the development of male plumage (kind of the opposite of the role testosterone plays in humans, where it restricts the development of female characteristics).

In some extreme cases, female ducks will actually develop testes, and essentially become male birds after the loss of the suppressing oestrogen hormones.

This bird was photographed in 2016 at Colusa National Wildlife Refuge.