Typical Ruby-throated Hummingbird call and sound of wings, at a feeder, August, PA.
Agonistic call (Aug, PA)
Sound of wings during the dive display in front of a female, where the male moves to and fro in a U-shaped arc (May, PA).
The Rufous Hummingbird chip is a higher squeaky chup, recalling junco (imm female, Jan, PA).
Anna's Hummingbird is similar but higher and harder (Delaware's first record, Dec).
Broad-tailed Hummingbird, a finch-like call (adult male with wing noise, June, CO).