Ravens
Common Ravens preening
A bird can’t preen its own head with its bill, so they use their feet to clean head feathers. In a few social species, like ravens, flock-mates preen each other.
Common Ravens preening
A bird can’t preen its own head with its bill, so they use their feet to clean head feathers. In a few social species, like ravens, flock-mates preen each other.
■ One of Aesop’s fables, “The Crow and the Pitcher,” tells the story of a thirsty crow that finds a pitcher with some water, but the water is out of reach in the bottom. By dropping pebbles into the pitcher, the crow is able to raise the water level and get a drink. This has inspired modern experiments testing various species in the crow family. Presented with a tasty treat floating deep inside a tube, the birds were able to solve the problem. They understood the value of large rocks over small, understood the right number of stones, understood that a tube of sawdust would not react to stones, and so on. The most accomplished species—the New Caledonian Crow of the South Pacific—showed a level of understanding of this problem similar to that of a five- to seven-year-old human.
A raven solving the puzzle
■ It seems counterintuitive that so many birds in hot climates are black, but studies have found that the advantages outweigh the disadvantages. Dark feathers do get hotter than white feathers, but because feathers provide such good insulation very little of that heat reaches the skin. In a light breeze, birds with black feathers actually stay cooler than white birds, because the dark feathers absorb light and heat at the surface, where it can easily radiate back to the air. White feathers allow light to penetrate into the feathers, closer to the skin, where heat is not so easily transferred back to the air. In addition, black feathers are more resistant to wear and help block UV radiation. Being black might also allow birds to be inconspicuous when resting in the shade, but conspicuous to their flock-mates when they are active.
Common Raven
■ Every bird is covered with feathers, and almost every feather on an individual bird is different, specialized in length, shape, and structure to match whatever function is needed at that position. Feathers around the head are all quite specialized, with tiny feathers around the eyes, feathers modified into bristles at the base of the bill, and longer feathers on the throat. Among the most specialized are the feathers that cover the ear opening. These must allow sound to pass through but also protect against debris and create a streamlined surface over the ear for air to flow across as smoothly and quietly as possible. The noise of air turbulence can reach 100 decibels in our ears at speeds as low as 25 miles per hour, the normal flight speed for most birds. That much noise makes it very difficult to hear anything else, and causes hearing damage in humans with long-term exposure. A smooth ear covering helps birds avoid both of those problems.
Some of the specialized feathers around the face; the ear covert feather is at the lower right.