Aptly named for its primarily dark slate gray plumage, the adult Plumbeous Kite is also distinctive for the white barring on its tail and extensive rufous patches on the primaries. When folded, the long, pointed wings extend beyond the relatively long tail. The bill is black and hooked, the legs are orange, and the claws are black. The eyes of adult Plumbeous Kites are a deep blood-red in color. Adult males are around 23 cm in length and 279 grams in weight, with females slightly larger. Apart from the difference in size, adult males and females are similar.
Immature kites have gray upperparts and whitish underparts with heavy, dark gray brown streaking. The rufous wing patches are absent, but the primaries often have some touches of reddish-brown. The bill is black with a yellow cere.
The Plumbeous Kite is highly similar to and thus difficult to distinguish from its congener, Mississippi Kite (Ictinia mississippiensis).
Plumbeous and Mississippi (Ictinia mississippiensis) kites are highly similar to one another, and are the only two species in the genus Ictinia. Based on morphology and behavior, the two have been considered by some to be conspecific (Sutton 1944) and by others to form a superspecies (Thioallay 1994). Although the breeding ranges of the two do not overlap, the Mississippi Kite migrates south and winters within the range of Plumbeous Kite (Peters 1931).
Both the Plumbeous and Mississippi kites are overall slate gray and share a similar shape, having a broad, round head and a compact body. Plumbeous Kite, however, is generally darker and has a shorter tail. Plumbeous Kite also tends to have more extensive and noticeable rufous wing patches, and lacks the white or whitish upper surface to the secondaries of adult Mississippi Kite. The tail is usually truncate in Plumbeous Kite but slightly forked in Mississippi Kite. Plumbeous Kite also has been described to have brighter feet. Among immatures, Mississippi Kite has a whiter, less heavily streaked chin, as well as broader brown - as opposed to grey - streaking in the underparts. Immature Mississippi Kites also have more “concealed white on the scapulars and wing coverts” (Sutton 1944).
The calls of Plumbeous and Mississippi kites are very similar (Sutton 1994), although the second note in the latter seems to be held for a longer time.
The following description is based on Ridgway and Friedmann (1950):
Adult: Sexes similar. Head, chin, throat, nape and underparts range from gull gray to dark gull gray. The undertail coverts are darker slate gray. Lores and circumocular region are black. Scapulars, interscapulars, and rump are slate to dark slate. The upperwing coverts and uppertail coverts are slightly glossy plumbeous black. The outermost primary is blackish slate, and the inner webs of the next six primaries are rufous. The innermost primaries and secondaries also are blackish. The plumbeous-black rectrices are marked by three white bars across the inner webs except on the median pair, which is simply black in color. Males and females differ only in size, with females being the larger of the two.
Juvenile: The top and sides of the head are streaked black and white. The remaining upperparts, wings, and tail are gray black to black, with white-tipped feathers. The tail is like that of the adults, but where the adults have rufous patches on the wings, the young have whitish patches, mottled with fuscous. The entire underparts are whitish, narrowly streaked with fuscous on the chin and throat, and more broadly streaked on the chest and middle of the abdomen. The streaks turn into bars on the flanks, thighs, and undertail coverts. The underwing coverts are also whitish with fuscous barring.
Nestlings: Natal down is reported to be white.
Bill black, cere bluish-black. The iris is a carmine-red. The tarsus and toes are a deep reddish orange or reddish yellow, and the claws are black.
Juveniles differ in that the cere is red-orange, the iris is a pale brown, and the legs and feet tend to be more yellow.
Total length: 33-37 cm (Howell and Webb 1995), 34.5-37 cm (Ridgely and Greenfield 2001b), 36 cm (Hilty and Brown 1986); wingspan: 84-94 cm (Howell and Webb 1995).
Mensural data (mm) for Ictinia plumbea (Ridgway and Friedmann 1950)
| || || mean || range |
| wing (mm) || male (n = 13) || 298.2 || 270- 313 |
| || female (n = 11) || 301.6 || 274-320.5 |
| tail (mm) || male (n = 13) || 148.5 || 123-167 |
| || female (n = 11) || 145.3 || 139-161 |
| culmen from cere (mm) || male (n = 13) || 16.6 || 15.5-18 |
| || female (n = 11) || 17.1 || 16-19.5 |
| tarsus (mm) || male (n = 13) || 38.5 || 37-42.2 |
| || female (n = 11) || 37.7 || 34-42 |
| middle toe without claw (mm) || male (n = 13) || 26.8 || 26-27.5 |
| || female (n = 11) || 26.3 || 24-29 |
Mass: male, mean 243 g (range 190-297 g, n = 16; Haverschmidt and Mees 1994); female, mean 257 g (range 232-294 g, n = 7; Haverschmidt and Mees 1994).