Purple Mallard?

Here's a Mallard I met last spring. But there's something odd here; instead of the green head that Mallards are known for, this one had a purple head. Or did it?

Generally speaking, Mallards can look this way in funky lighting. If you followed the Mallard around long enough, you'd eventually see the green head we're used to seeing. As you might expect, this isn't something that only happens with Mallards; people have also reported it in Northern Shovelers. Birders will sometimes see and/or get pictures of birds that show almost none of their blue, showing drab-looking Bluebirds, Blue Grosbeaks, and Indigo Buntings.

I suspect that this is partly due to the way blue coloring is produced in (almost?) all animals. Unlike most colors, when you see a blue animal you're not seeing blue pigment, you're seeing black coloring on surfaces that are structured to scatter light and appear blue. (If you grind up a blue feather from a bird finely enough, you won't see blue because you'll have destroyed this "structural blue" coloring.)

May 13, 2021 at the Raritan River Greenway
Photo 132037689, (c) jpviolette, some rights reserved (CC BY-NC)


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