A male Scarlet Tanager in the process of molting
This bird is molting from bright red summer plumage to greenish winter plumage, typical of August. Demanding activities like nesting, molting, and migration usually do not overlap, and birds have evolved an excellent sense of time and a strict schedule to make it all work.
■ Consider how a tanager sees the world as it moves through a lattice of slender twigs suspended above the ground. The bird gives no thought to hopping from twig to twig eighty feet up in the air, then jumping into the open air to catch a passing insect, or flying across a fifty-foot gap to the next twig. Can birds be afraid of heights? Some fear of heights is instinctive and adaptive. Walking off a cliff would be bad, so most animals, including baby birds, instinctively avoid the edge. Once a bird can fly, the cliff poses little danger, and they are comfortable balancing on the edge or even stepping off, knowing that they can spread their wings and come right back. An adult bird must have some understanding of how bad a fall could be, but at the same time confidence that it won’t fall.
A Western Tanager perched above the forest canopy
■ Preening is one of the most essential chores a bird has to do, and they spend a lot of time doing it. Typically they preen for about 10 percent of each day, but it can be over 20 percent. Some details of the bill shape of birds have evolved specifically for preening, and a few species have specialized claws for feather care. The main functions are to remove parasites and to clean and adjust the feathers. Birds have a gland at the base of their tail that produces an oil used for feather care. Preening typically involves reaching back to this preen gland, getting a little oil on the bill, and then using the bill to carefully tend to each body, wing, and tail feather from base to tip. This resets all of the barbs and straightens the feather, while also spreading oil across it. A session of preening often ends with the bird leaning forward, raising all of the feathers away from the body, and shaking like a wet dog, sending bits of dust and down floating away.
Typical preening motions
■ Many birds eat fruit, and most fruit has adapted to be eaten and dispersed by birds. The nutritious outer layer of the fruit attracts birds, and fruit up to pea-sized or even larger is easily swallowed whole by birds. Once swallowed, the fleshy part of the fruit is digested, and the hard seeds are either regurgitated or excreted, intact, usually within a few hours. In this way birds disperse seeds widely across the landscape. One study found that birds migrating from Europe carry viable seeds to the Canary Islands, across several hundred miles of ocean.
A Scarlet Tanager eating elderberries