I came across a pair of Bushtits building their characteristic hanging-sock nest. Construction was well along, but there were still gaps in the weaving of moss, spider webs and other materials.
Here is the male, bringing carrying something soft and fluffy looking. Lichen? Innards of a lost stuffy? He took it inside, and a few seconds later darted out.
He was followed by the female. (Notice the pale eye? Males' eyes are dark.) She was in and out in a flash
The male returned, carrying a...caterpillar? There are young already? Rearing while still building? Renos are hard when there's Lego and Polly Pocket all over the place. (Speaking from experience.)
A closer look shows the object in his bill isn't animal. I'm not sure what it is, but it seems to more for building than eating.
On it went, taking turns, back and forth. The nest was just off a trail in a park, about 8 feet up, not as secure as one would hope. I figured I had given them enough unwanted attention so wished them luck and continued on my way.