The white-tailed kite is a mostly white, falcon-shaped, raptor fifteen to seventeen inches long. The adults have pale gray backs and upper wings, with the head, under-parts and long tail all white. (2). The underwing coverts are black as are the scapulars on the back (3).
There is little difference between the sexes, except the females tend to have darker backs than males (3). The short legs and feet are yellow, the bill black and the eyes red (3). Young kites have brownish areas on the breast and back, a dark band on a pale gray tail (2) and yellow eyes (3). Molts occur from summer to fall and possibly longer, with the primaries being renewed starting from the inner feathers (3).
Although kites are normally mostly silent, three different calls have been identified during the nesting period (8). The most common call is “keep” (3), emitted singly, or repetitively at intervals of a second or two (3). This call is used for occasions involving territorial maintenance, pair recognition or notification and interaction with young. A second call, “eegrack” (3) often repeated many times, is used mostly for functions involving pairing, incubation, and the feeding of older chicks. A third territorial call, “grrrkk”, also repetitive, is used when chasing away intruders (3).