We've been watching this one since April as she sits in a tree or on a branch overhanging the pond.
Once she spots an insect, she flies off the branch, snatches the insect mid-air, and returns to the branch to eat it. This is called “hawking”, a behavior shared with other members of the flycatcher family.
Once she started flying under a deck nearby with freshly caught food items, we suspected she was feeding babies.
Sure enough, two small Phoebes peeked out over the edge of the nest.