Nest Building Puzzle:

Tree Swallows nest in tree cavities, but will also use manmade nesting boxes. They feed on small, aerial insects that they catch in their mouths during acrobatic flight. They breed in open habitats such as fields and wetlands, usually adjacent to water.

https://www.allaboutbirds.org/guide/Tree_Swallow/id

A Tree Swallow entertained me in the morning as I watched her attempt to maneuver a long piece of nesting material, more than double the length of her body, into a hole that was only 1.5 inches in diameter. She made 6 fly-in attempts while I watched from a distance.

After each unsuccessful attempt, she flew back to the same branch on a nearby tree where her mate was supervising the activity. (He didn't offer to help.)

The determined bird sized up the situation one last time and managed to get most of the twig into the hole. One more piece of the nest puzzle was complete!