The males have bright red crowns, chests, and underparts, with brownish wings and tails.

They also practice within-species brood parasitism, whereby females lay their eggs in the nest of another individual.

Females build shallow open cup nests and incubate the brown-speckled whitish eggs.

The overall population numbers are in the millions, thus the International Union for Conservation of Nature considers it a species of least concern.

The tyrant flycatcher family, Tyrannidae, is a group of passerine birds present only in the Americas; its members are generally drab in coloration.

The identification was based on specimens brought back by Charles Darwin on the second voyage of HMS Beagle, which lasted from 1831 to 1836.

[4][5] The species was then designated as Pyrocephalus rubinus by the English zoologist George Robert Gray in 1840, based on Darwin's specimen taken from James Island.

[11]: 278  The common name comes from its vibrant coloration and its membership in the flycatcher family, which is reflected in its insect-rich diet.

The flight feathers and wing coverts are slightly paler gray, which create a barring effect.

[2] Worn feathers are replaced by molting, which takes between 62 and 79 days and begins in July, lasting until September.

A 2013 study determined that monsoon rain patterns do not affect molting, as had been previously expected.

[2] The flight song is given by males who fly high above the canopy, and is described as a pt-pt-pre-ee-een by the Cornell Lab.

Their wings may also be used to create a whirring noise while perch hopping or during territorial displays, though this is practiced infrequently.

North American populations generally migrate by late August and return between February and April.

[2] Vermilion flycatchers are generally solitary, though they may form small flocks of not more than five individuals during winter.

They spend most of their time in trees perching, landing on the ground only rarely to catch insects.

They also practice intra-specific brood parasitism, where females lay their eggs in the nest of another vermilion flycatcher.

Courtship involves the male fluffing his crest and chest feathers, fanning the tail, and engaging in a fluttery flight while singing to a female.

[22] Egg-laying begins in March and runs through June; eggs are laid once a day in the early morning.

Re-using nests saves time and energy but perhaps at the cost of a higher parasite load.

[2][23] The vermilion flycatcher feeds mostly on insects such as flies, grasshoppers and beetles—though the exact composition of the diet is poorly studied.

Unusual reports of predation include by a scrub-jay, and a group of live nestlings eaten by fire ants.

Yearly nesting success (the percentage of laid eggs which were raised to fledglings) in a Texas study varied from 59 to 80%.

[28] Avian pox viruses and crop canker (caused by Trichomanes gallinae) may have directly contributed to the extinction of the Galapagos sister species.

This acts as an indicator of genetic fitness to potential mates, as a bright male is using his diet-based coloration to show off his ability to survive and catch food.

[31][32] The Audubon Society of Tucson, Arizona, publishes an eponymous journal named for the vermilion flycatcher.

Once prolific in southern California, it has become increasingly rare, although it is expanding into new areas such as Florida and Oklahoma.

Vermilion flycatchers have adapted to human structures by increasingly nesting in parks and golf courses.

A prime example is along the Lower Colorado River Valley, where changes in water management combined with the destruction of cottonwood-willow riparian habitat have led to the loss of almost all breeding and foraging areas.

[2] The San Cristóbal flycatcher, which was once considered part of the species, was endemic to the Galápagos Islands but went extinct sometime between 1987 and 2012.