- May 5 - Lower Columbia Basin Audubon Society First Saturday Bird Walk, 8:00 AM at Bateman Island, by special permission.
Arrive early (~7:45 AM).
- Peregrine Falcon males are courting the larger females.
- Ospreys return and begin readying their nests near water where fish are abundant.
- Evening Grosbeaks return to bird feeding stations for sunflower seed treats.
- Migratory departures - Snow Geese, American Widgeon, Surf Scoter, Dunlin, Ruby-crowned Kinglet, Gold-crowned Sparrow.
- Migratory arrivals - Western Tanager, Black-headed Grosbeak, Bullock’s Oriole, Vaux's Swift, flycatchers, Western Wood-Pewee, Swainson’s Thrush and Yellow Warbler.
- Penstemon, a favorite flower of hummingbirds, butterflies and bees, blooms.
- Black Cottonwoods shed their cottony seeds on breezy days.
- Western Tiger Swallowtail butterflies visit flowers.
- Turquoise-colored male Lazuli Buntings sing while rich brown females incubate eggs.
- Eta Aquarids meteor shower is early-May.
- International Migratory Bird Day is mid-May.