First of Season (FOS) Birds

One of the joys of birding is to keep track of the changes in birdlife through the seasons. The first bird of each returning migratory bird species that a birder sees is considered a First of Season (FOS) sighting. FOS sightings can be of northbound migrants or arriving breeding species in spring, southbound migrants in fall, or arriving wintering birds in late fall.

Today on my four mile walk, a heard a FOS Eastern Phoebe near one of the bridges over the Perkiomen Creek near my house. I've written before about how these birds are probably direct descendants of the phoebes that John James Audubon watched closely at his farm 20 miles downstream on this same creek. They leave for the winter, but its nice to see them back.