An adult tropical kingbird is long and weighs. The head is pale gray, with a darker eye mask, an orange crown stripe, and a heavy gray bill. The back is grayish-green, and the wing and forked tail are brown. The throat is pale gray, becoming olive on the breast, with the rest of the underparts being yellow. The sexes are similar, but young birds have pale buff edges on the wing coverts. Tropical Kingbirds appear to be monogamous. In most parts of the species' range, they are permanent residents and remain together in pairs year-round. The call is a high-pitched twittering trill, tree-e-e-e-e-e-e, with a more complex version sung by the male at dawn. Their breeding habitat is semi-open areas with trees and shrubs, including gardens and roadsides. Tropical kingbirds like to observe their surroundings from a prominent open perch, usually high in a tree, undertaking long flights to acrobatically catch insects in mid-air, sometimes hovering to pick food off vegetation. They also eat some fruit from such diverse species as tamanqueiro, the Annonaceae, Cymbopetalum mayanum and gumbo-limbo ; foraging for these even in disturbed habitat. As they keep mainly to the upper levels of trees, they find little profit in following mixed-species feeding flocks in the understory. These birds aggressively defend their territory against intruders, even much larger birds such as magnificent frigatebirds, toucans, caracaras or hawks. In a study in Parque Nacional de La Macarena of Colombia, parasitism by microfilariae and trypanosomas was infrequently recorded in tropical kingbirds. The male and female inspect potential sites together before selecting a site, typically a fork or crotch high in a tree but sometimes just a few feet above water. The female builds a bulky, sloppy-looking, shallow nest of vines, rootlets, twigs, weeds, and grasses; it is unlined or lined with hair. Nests average about 5.2 inches across and 3 inches tall, with interior cup about 3 inches across and 1.6 inches deep. The female incubates the typical clutch of two to four eggs for approximately 16 days, and the nestlings fledge in another 18 or 19 days. The eggs are whitish or pale pink with variable amounts of dark blotching. The tropical kingbird is one of the most widespread and conspicuous inhabitants of open forest, forest edge, scrub and agricultural land from the southwestern United States south to Argentina. As a result, the bird is considered as being of Least Concern and their population is increasing, according to the IUCN. According to Partners in Flight, global estimates of tropical kingbird breeding population is around 200 million. They rate the species as 4 out of 20 on the continental concern scale, indicating that this species is of low conservation concern.
