Beaks, Bones, and Bird Songs by Roger Lederer

Author:Roger Lederer
Language: eng
Format: epub
Publisher: Timber Press
Published: 2016-07-16T16:00:00+00:00

DEALING WITH HEAT

Heat stress (hyperthermia)—elevated body temperature—appears, overall, to be more severe than cold stress (hypothermia) in birds. Overheating is a common problem faced by poultry producers, as too high an ambient temperature causes a loss of body and egg weight and poor quality meat. But overheating is also a concern for wild birds, more so now with increasing global temperatures. In January 2009, thousands of birds, mostly parrots, died in Carnarvon, Western Australia, when the temperature reached 113°F; the following year 208 Carnaby’s Black Cockatoos, an endangered species, were found dead when the temperature hit 118°F. A small bird can lose 5 percent of its weight every hour at that temperature, leading to dehydration and eventually death in a matter of hours.

Birds have many morphological and physiological adaptations that allow them to respond to a range of temperatures and survive with little or no stress. As the ambient temperature increases, physiological mechanisms approach their limits and behavioral mechanisms come into play. Here are some of those adaptations and mechanisms for surviving the heat:

BILLS THAT RADIATE HEAT The toucan’s bill has always been fascinating but it was made even more so when a new role for the Toco Toucan’s bill was revealed in 2009 via infrared thermography. With a large and colorful bill used for picking fruit and capturing small animals, this tropical South American bird also employs its beak to radiate body heat. The surface area of the bill covering is about half of the body’s total surface area, uninsulated, and well supplied with superficial blood vessels. While flying, the toucan might increase its metabolic heat production by a factor of 10–12, so in a warm tropical environment the bill is an important source of heat loss. Another indication that the bill radiates heat is the toucan’s common practice of tucking its bill under a wing and folding its tail forward over the bill while at rest to reduce heat loss. Relative to its body size, the Toco Toucan has the largest radiator in the animal world, even compared to the ears of elephants.

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