The scarlet tanager is described as being a somewhat secretive bird (2), and prefers to spend its time high up in the forest canopy (2) (4) (6). This striking bird is a strong flier, and is capable of long, continuous flight (3). In fact, the scarlet tanager is the most migratory of all tanager species in terms of the distance it travels (3).
Migration occurs primarily at night (3) (6), with the scarlet tanager departing from its wintering grounds from around February, although the exact timing of departure varies depending on the location (3). The scarlet tanager flies across the Gulf of Mexico, reaching the breeding grounds by late April or early May (6). Following the breeding season, which lasts from May to July (7), the birds migrate southwards again in the autumn (6) (7), either singly or in small flocks (6).
Male scarlet tanagers arrive on the breeding site first (3) (7), and establish territories which they advertise by singing almost continuously from a high, conspicuous perch (3). The scarlet tanager is believed to be seasonally monogamous, and is not thought to have the same mate in successive years (3).
The female scarlet tanager selects the nest site (3) (7), which is almost always on a horizontal tree branch (2) (4), and builds the nest alone (3) (6) (7). The nest is usually a rather flimsy, shallow, open cup (2) (4) (7) formed mainly of twigs, rootlets and plant stems (2) (6) (7). Finer materials such as grasses are used to line the nest (6) (7).
The scarlet tanager only produces one brood per season (6) (7), which contains between two and five eggs (7), with four being the most common (3) (6). The eggs of the scarlet tanager are bluish-green to light blue in colour (2) (3) (6) (7), and are speckled with brown, chestnut-red or purplish-red spots. This spotting is usually more concentrated at the larger end of the egg (3) (6) (7).
Incubation of the eggs is carried out by the female scarlet tanager, who is fed on the nest by the male (3) (6) (7). The incubation period is between 12 and 14 days (3) (7), after which time the helpless, orange-skinned young hatch (3). Fledging time ranges from about 10 days (6) to 15 days (7).
The diet of the scarlet tanager consists mainly of insects (3) (4) (6), particularly during the breeding season (3) (7), although fruit from a wide variety of trees is also frequently eaten (3) (4) (6) (7). The scarlet tanager gleans insects from leaves and fruit (2) (3) (6) (7), or catches them on the wing (2) (4) (6). Preferred insect prey includes bees, wasps, caterpillars and moths (3) (6) (7), but spiders and dragonflies are also consumed (7). Young scarlet tanagers are fed insects and fruit (3) (7) by both the male and the female (3) (6) (7).