Scarlet Tanager male
Some birds with exceptionally brilliant, conspicuous plumage elude detection and maintain their privacy right in our midst. American tanagers, like most other neotropical migrants — birds that winter in the tropics and breed in North America — migrate at night when hawks and falcons sleep. Cooler air and lighter winds make their marathon journey less physically taxing, and they can use the daytime to forage for food.
Scarlet Tanager male
Tanagers arrive on their breeding grounds under cloak of darkness and, despite gaudy feathers, get busy with nesting activities unnoticed by most human observers. Even savvy birders who recognize the burry songs of tanagers (often compared to a robin with a sore throat) may be hard-taxed to find the brilliantly colored singer among the leaves.
By the time they arrive, their hormonal levels are peaking. Males almost instantly start claiming and defending territories. The male Scarlet Tanager‘s display is the most elaborate, performed from within tree branches below where the female is perched. Opening his wings and stretching his neck forward, he makes his brilliant red back appear as long and large as possible to contrast with his black wings and tail.
As soon as he arrives on the breeding grounds in spring, the male Western Tanager starts singing his throaty, robin-like song from a high perch to advertise his territorial claim. Pairs may have already formed, since the female often starts building a nest as soon as she arrives. Females sing, too, but usually only after the eggs have hatched.
The Western Tanager nests high in a tree, usually on top of a branch well away from the trunk or hidden in a clump of pine needles. The female builds a flimsy, shallow cup of twigs, grasses, hair, or fine plant fibers and incubates for about 13 days.
Scarlet Tanagers arrive right as trees are starting to leaf out. Males have only a few days to claim a territory before females arrive, and try to attract their mate before the foliage grows dense, blocking the females’ view. Fortunately, females make fast decisions and quickly get down to business.
A rare sight, this Summer Tanager nest contains three eggs. The nest is an open cup of dry grass or other plant fibers, located high in a cluster of leaves or the fork of a horizontal branch, often hanging over a road, dry creek bed, or other opening.
In all three tanager species, the female takes three or four days to build the nest. Males don’t assist but sing frequently and bring the female food, reinforcing their pair bond, just as a human who isn’t good at home improvement projects might play music and bring pizza for the spouse doing the work.
Tanager nests are typically set so high in trees, in branches away from the trunk, that they are hard to observe, and so there are gaps in our data. We know that Scarlet and Summer Tanagers start incubating the eggs as soon as the last egg is laid; that’s probably true of Western Tanagers too.
Males make frequent food runs while the females incubate. The eggs hatch in 13 or 14 days. The chicks have a bit of fuzzy down and their eyes are sealed shut. If one is suddenly touched, or if the nest is tapped (as by a parent alighting on it), the chick pops up, mouth open, like a little jack-in-the-box. Usually both adults feed the young, though some males give food to the female to pass to the chicks. Feeding bouts start at first light and continue all day, about every 10 or 15 minutes.
Tanagers eat a lot of fruit, in both the tropics and the north, but during nesting season need a lot of protein, which they get from insects and other small invertebrates. The Summer Tanager specializes in bees and wasps. Its bill, longer than that of its relatives, may help protect its face from stings when it snatches large wasps. All three tanager species catch caterpillars and other insects with ease. Tanagers catch the bulk of their meals high in leafy trees, where they conduct most of their activities.
Newly hatched. A Summer Tanager pair at their nest with begging nestlings. Altricial, the young depend entirely on their parents for food and protection. Their eyes remain closed for five to six days after hatching, and their gapes are edged with yellow flanges.
Feeding time. This Scarlet Tanager pair has just fed one of three nestlings. The young have sparse grayish down on their orange skin, yellow gapes, and closed eyes.
The nestlings grow quickly. Pinfeathers start erupting by the second day, and their eyes start opening on about their fifth day. By seven days old, their feet are strong. If a predator scares them out of the nest at this point, they may be able to survive if they land on a branch or can hop into a low shrub, because their parents will hear their begging sounds and continue to feed them even off the nest. Their chances of surviving grow each day that they safely stay in the nest; the luckiest don’t leave until 12 days old.
8 days old. A male Western Tanager passes a beakful of caterpillars and a fly pupa to his mate as they feed their young. Both parents feed the young, but the male sometimes passes the food to the female if both are present. The nestlings’ eyes open about 7 days after they hatch.
9 days old. Western Tanager nestlings are fed by their father. In addition to larvae, they are fed adult insects as large as dragonflies, and berries, if available.
Housekeeping. A male Western Tanager removes a fecal sac from the nest. For the first 4 days after hatching, the adults eat the fecal sacs, then switch to carrying them away. Older nestlings defecate over the edge of the nest, and their parents grab the sacs so they won’t attract predators.
Ready to fledge. A 10-day-old Western Tanager nestling tries out its wings while standing on the nest rim. These young fledged the day after the photo was taken.
When the young birds fledge, they remain on their parents’ territory and continue to be fed by them for at least a couple of weeks. At first they’re poorly coordinated and sit quietly, preening their still-developing feathers and studying the world around them, sometimes snapping at nearby insects. As they begin flying more strongly, they figure out how to find their own food.
Male Scarlet Tanagers molt into brilliant red feathers in late winter in the tropics. They molt into yellow feathers after breeding, between July and September.
How do tanagers learn their migratory routes? Many nocturnal migrants learn star patterns during their nestling and/or fledgling stage. In planetariums, scientists have discovered that nestlings and fledglings of some species identify the star that is always seen in the same place (Polaris, also known as the North Star), and use that to identify north. Many nocturnal migrants have also been shown to have tiny bits of magnetite in their brains, giving them an actual built-in compass. Birds such as tanagers may be depending mostly on star patterns when the sky is visible, and using their built-in compass as a backup.
It’s unlikely that tanagers migrate in family units, so the young birds must orient and navigate on their own during their first migration. As do many fruit-eating birds, Scarlet and Western Tanagers associate in flocks on their wintering grounds, so young may figure out where to go and how to survive in the tropics by listening for and observing other tanagers.
