The Blue-gray Gnatcatcher (Polioptila caerulea) is a very small songbird, 3.9–5.1 inches in length, Adult males are blue-gray on the upper parts with white underparts, have a slender dark bill, and a long black tail edged in white. Females are less blue, while juveniles are greenish-gray. Both sexes have a white eye ring. Breeding males have a black V on the forehead.
They forage actively in trees or shrubs, mainly eating insects, insect eggs and spiders. They may hover over foliage (gleaning), or fly to catch insects in flight (hawking).
The tail is often held upright while defending territory or searching for food.
The songs (and calls) are often heard on breeding grounds and occasionally heard other times of the year. Calls: "zkreee, zkreee, zkreee", Songs: "szpree zpree spreeeeey spree spre sprzrreeeee"