Looks like a Yellow Warbler hard at work building a nest. In reality this warbler was caught in the act of stealing nesting material from an Eastern Kingbird nest. Within a 50 yard radius there are at least 4 nests belonging to 4 different species of birds. Just a short walk down the same trail is a Baltimore Oriole nest. A 30 second stroll from the Kingbird nest is yet another nest (species unknown but warblers can be spotted flitting about nearby).

Another photographer, Saul, pointed out the Kingbird nest to me....although I likely would have found it in due time. The nest itself is blended in well with the surroundings and not easy to see but the Kingbirds are very active and would eventually have led me or anybody else to the nest site.

Just a mere hop skip from this nest is a Yellow-bellied Sapsucker nest and a Great Crested Flycatcher nest practically right next to each other. A Tree Swallow nest is in the same group of trees. If you walk slowly down this trail you'll eventually see it as the birds tend to hang around pretty much in the open.

For more info about Petrie Island see: http://www.fallingbrook.com/petrieisland/birdlist.htm