The most notable feature of E. forficatus is the deeply forked swallow-like tail, which distinguishes this kite species from its relatives, Mississippi kites and white-tailed kites. The structure of the tail enables this kite to fly well at low speeds. The wings are long and thin, enabling flight at high speeds as well.

Swallow-tailed kites are monomorphic. Adults have black wings with white undersides, white heads, necks, and underparts. The tail and upperparts are iridescent black, with streaks of green, purple, and bronze. Juveniles look similar to adults but with slightly streaked heads and underparts, as well as shorter white-tipped tails.

Swallow-tailed kites have a body length ranging from 49 to 65 cm. Wingspan is from 114 to 127 cm. The average weight of maled is 441 g and the average weight of females is 423 g, although females may be slightly larger in size.

Range mass: 423 to 441 g.

Range length: 49 to 65 cm.

Average length: 58 cm.

Range wingspan: 114 to 127 cm.

Average wingspan: 122 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike; female larger