Think of a dog on a hot summer's day. Chances are your mind's eye will see a pink tongue lolling, busily moving air to generate some handy evaporative cooling. Think of a bird in a similar situation and a glistening tongue doesn't really come to mind.
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But birds pant too, and they do it for the same reason as dogs. While dogs can sweat a little, birds can't sweat at all. For them, panting is a last resort.
Birds are hot little creatures. Their normal body temperature sits between 39 and 43 degrees Celsius; much hotter than mammals. So what happens when you're naturally super-hot, wearing a feather doona, and a hot day in summer hits 45 degrees?
Unfortunately, like everyone else, birds have to obey the laws of physics. Energy can neither be created nor destroyed. If the air is 45 degrees, you're going to wind up at a similar or higher temperature, unless you send your heat somewhere else.
Birds have five options.
The first two are linked. Radiation and convection send heat out into the air, which expands and rises, moving away. You can spread your wings to expose the sparsely feathered skin beneath, and increase the blood flow to your wattles, combs and feet.
A breeze helps too. But none of this works if the air is hotter than you are.
Or you can try conduction. Just snuggle up to a cooler object, like a wall or the ground, and transfer across some heat. Pretty effective, as long as there's something cool around.
And you can poop out heat if you have to, but it doesn't work well and there's only so much pooping you can do before you run into trouble.
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Which leaves using heat to evaporate water.
Like dogs, birds do it via their respiratory system, some even flutter the muscles in their throat to help. But evaporated water needs to be replaced, and if it's too hot the amount of heat that needs to be shed can exceed the physiological capabilities of the bird.
Heat waves in Australia regularly lead to bird deaths through dehydration and hyperthermia. This worsens during drought years. Small birds are particularly at risk.
As the climate becomes hotter, what can we do to help?
For wild birds, it's essential that we protect their natural habitat; dense vegetation, rock formations and watercourses provide shade and a cooler environment to seek refuge in.
For domestic birds, we need to ensure access to cool water and cool areas. Even the fine mist from a hose can be a lifesaver.
We should all do our bit to reduce our carbon footprint in a warming world. Our feathered friends will thank us.
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