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by Giovana on set.19, 2012, under japan
Birds pant to beat summer’s high heat
Have you noticed any birds with their mouths hanging open lately?
I watched three crows perched in a tree over a downtown sidewalk. The jaws of all three looked locked in some odd, open mouth position. My car thermometer read 97 degrees.
A photograph of the Forster terns featured with last Sunday Birdlife column showed all three terns with mouths wide open and tongues raised. The temperature was in the high 90s.
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An open mouthed American robin walked across my parched brown lawn in search of food. And the mockingbirds have been sitting around with gaping mouths as they guard the unripe berries in pokeweed patches.
The barred owl on display at Ijams Nature Center was holding its mouth open and fluttering its throat. A barred owl open mouth looks a lot like a wide toothless grin.
We had a month long heat wave. An open mouth is one sign that a bird might be overheating and working to lower its body temperature.
Birds lack sweat glands, so they don sweat to cool off like people do. Birds pant like dogs. By opening its mouth and breathing faster, a bird increases the airflow. This causes more moisture to evaporate from the mouth, tongue, throat and respiratory tract.
Evaporation of moisture has a cooling effect on the body. However, a bird can lose an awful lot of water that has to be replaced.
Larger birds such as herons, cormorants and pelicans flutter the upper throat to increase the evaporative cooling process even more. Some small birds which usually have higher body temperatures than large birds lose moisture through their skin.
Like people, birds are able to maintain their internal body temperature as the environmental temperature increases or decreases, but only within limits. A bird body temperature may vary a bit during the day.
Once the environmental temperature rises above about 92 degrees, a bird body may start to overheat and lose water. A bird will pant or take other actions move around less or seek the shade to reduce its body temperature. Birds ruffle and raise their body feathers so hot air close to the skin can escape. We see fewer birds when it hot because birds are less active in order to stay cool and conserve water.
The internal body temperature of different bird species ranges from a low of about 98.6 degrees in penguins to a high of about 112 degrees in hummingbirds and swifts. Small birds are likely to overheat if the environmental temperature is higher than their body temperature. A cardinal temperature is about 109 degrees. An environmental temperature above 113 degrees can be deadly to some bird species.
Birds also give off excess body heat through their unfeathered legs and feet. Leg arteries dilate and carry more blood to the legs and feet, which heat up. The heat from the warm blood radiates out away from the body. If a pigeon body is experimentally warmed, the temperature of its feet can rise more than 50 degrees while its body temperature remains constant.
A refreshing dip in a birdbath helps a bird keep cool. Water is far more effective than air in transferring heat away from the body. Water will cool a bird legs four times faster than air. Birdbaths also help provide the extra drinking water that birds need to beat the heat.
