Birds and mammals like us, are homeothermic. We often say “” is a misnomer as tuna and lizards and worms and tuna can be warm blooded at times. Better to say homeothermic which means which means that mammals and birds maintain a fairly constant body temperature at all times. To do that we have to use a lot of energy to maintain that temperature and shiver to stay warm or sweat to cool off when necessary. Birds have a bit higher metabolism than mammals, are generally smaller, and use more energy to warm up or cool down as necessary.
The world has been experiencing record high temperatures lately. Government and private agencies are making efforts to see that the homeless, the elderly, and poor have some way to escape the heat and humidity. A heat wave in Europe a few years ago killed hundreds of people. Global warming is making our environment hatter each year.
What about the birds caught in this heat? How do they cope with it? Unlike mammals, birds have no sweat glands. Mammals, like us, exude droplets of water from our sweat glands with little physiological effort. If birds had sweat glands that emitted moisture, their feathers would mat down from the moisture and they would be unable to fly. Instead, they cool themselves primarily by panting. Breathing in and out rapidly removes moisture from the lungs and throat, and like sweating, the loss of moisture off these tissues serves to cool them. The panting of birds works as well to cool them, up to a point. When we exercise, we heat up and sweat more. When birds pant, they use energy which generates even more body heat, requiring even more panting and more energy use. The House Sparrow breathes 57 times a minute at 900 F and 160 times a minute at 1100 . The point of diminishing returns comes quickly, and birds die fairly quickly in high temperatures. Some poultry raisers, in the event of a disease epidemic among their collection of birds which cannot be contained any other way, kill the birds simply by raising the temperature in the birds’ environment to a lethal level.
Besides panting, birds do have a few other mechanisms to prevent overheating. They can lose a bit of body heat off their skin by raising their wings and body feathers. Birds avoid the sun by resting in the hottest part of the day, or if incubating eggs in the open, they orient their back to the sun. They will also shade the eggs or young. Albatrosses raise their feet off the ground and spread their wings to shade their feet. The Herring Gull orients the white part of its body towards the sun to reflect heat. The Wood Stork, when hot, directs its liquid excrement onto its long legs. Cooling with liquid excrement is way is called urohydrosis. The domestic chicken splashes water over its comb and wattles. The Egyptian Plover wets its belly in puddles and cools itself and its eggs and the sand around the nest. Pelicans and cormorants vibrate their large throat pouches (called gular fluttering).
I received an e-mail the other day from some New Yorkers, asking what to do about the pigeons nesting outside their office windows. The parent birds are panting endlessly and the chicks are dying. It’s hot in many places. Birds don’t need feeders in the summer, but a bird bath would be a welcome addition to your yard.