Domestic Mallard

Description:

Mallard-sized pair of ducks, assumed male (darker) and female (lighter). Gray heads and necks, yellow-orange beaks, brown/buff chest fading to white further back on the body, but with gray (light gray) tail feathers.

Habitat:

Pond near a volcanic black sand beach, tropical climate (Hawaii).

Notes:

I've looked on Hawaiian bird sites, and Wikipedia and can't find anything that looks quite like these to identify them. I'm told ducks inter-breed easily, so maybe they're the result of that, but the pair seem so perfectly matched (apparent male/female darker/lighter combination, I thought there might be a specific species for this).