Okay, here are the mystery feathers from last night:
I realize that was tough because there's not much context, so here are a few hints.
I encountered the feathers in a coastal grassland. Along with the feathers shown above, some had even more white:
Most of the other feathers in the area were brown with darker barred patterning. The longest feathers I found were ~5-6 inches (12-15 cm) long.
I was moving along, scanning the various feathers, trying to put together a picture of the bird's identity. Along with the tail and wing feathers shown above, there were brownish body feathers with somewhat similar colors and markings:
Then I looked ahead and spotted some feathers that clinched the identification. I think the next photos will help you figure out the identity of this medium-sized grassland bird, too:
The bright yellow and black body feathers, along with the large amount of white on the outer tail feathers, leads to Western Meadowlark (Sturnella neglecta).
I don't recall encountering meadowlark feathers before. It was fun to see the patterns up close. I also wondered what happened to it — who caught the meadowlark? A falcon? A harrier? Have you seen a predator chasing adult meadowlarks?
(I just tried to learn more about meadowlark predators. Along with falcons, I was somewhat surprised to see Great Egret and Burrowing Owl listed as possible predators on adult meadowlarks. Who knew?)