Summertime gets hot out there, and birds have unique challenges to avoid overheating. We call birds and mammals “warm-blooded” but we really mean is they are endotherms: they must maintain a constant body temperature regardless of ambient conditions. Typical bird internal temperatures are constantly within a few degrees of 105°F (41°C), which improves their chances of survival. They can be active throughout the day, the year, and all over the world. Their fast metabolism also means nerve impulses are faster, and their muscle strength and physical endurance are greater, for their size. So it’s worth it, even if that constant body temperature is challenging to maintain.
Most of the time ambient temperatures are lower than that and birds have a variety of strategies to deal with cold conditions. But occasionally conditions are too hot and a bird will die without a way to keep cool (proteins start denaturing above 104°F, and that scrambles not just muscle tissue but also skin, nerve, bone tissue, enzymes and more). You can probably relate to their dilemma. The outside temperature doesn’t need to be 98.6° F (37°C) for us humans to feel uncomfortable or develop heatstroke, and unlike us, birds can’t go inside and turn on the AC.
Some reasons why birds are especially vulnerable:
- birds are tremendously active and quick-moving which generates much internal heat
- birds are busy constantly and that increases the likelihood of being out in the sun, where they will get many degrees hotter. A surface receiving direct sunlight absorbs energy, raising the temperature — true for a thermometer or a creature’s body.
- summer is still nesting season for many birds, when they are busier than usual, foraging for many, coming and going
- birds are small, which means they have relatively large surface area over which to absorb ambient heat
- birds cannot sweat, like mammals, so they cannot cool off by evaporation
- birds are covered in insulating feathers making it difficult to expose skin where air can blow body heat away
So, how do they keep cool?
1. Panting allows evaporative cooling across respiratory tissues. You may have seen birds with their beak open on hot days — that exposes moist tissue. For water to evaporate from a surface it must absorb heat energy from that surface, which is why wet skin feels cooler than dry skin, and why high humidity slows that way down, the air unable to take up any more water vapor.
The Great Blue Heron below is not only panting but spreading its wings to help cool down its body.
GBH
Some birds increase evaporative cooling with gular fluttering, a vibration of their neck skin. Birds who tend to be out in the open much of the day either feeding or roosting will do that, such as cormorants, pelicans, boobies, anhingas, frigate-birds, herons, owls, doves, roadrunners, nightjars, and groundbirds.
.
2. Bare skin on birds’ feet, legs beak and even eye-rings is another place for evaporative cooling.
hen Wild Turkey and poults
Some birds, like vultures and storks, will even excrete fluid onto their legs to increase that (technical term: Urohidrosis). The white on the lower legs of this White Stork is excretion.
White Stork
Keel-billed toucan
Toucans have blood vessels in their bill where heat loss can be actively increased or decreased depending on outside temperature.
For a thermal image of a toucan cooling off, see photo here:
A Bird With a Big Air-Conditioning Bill
3. Bathing not only helps birds get clean but it also gets water down between feathers to their skin, where evaporative cooling can take place. Sitting in water dissipates body heat into cool water. Birds often fluff up and flutter their feathers after a bath to increase that.
baby Red Crossbills
4. On hot days birds become inactive during the middle of the day. Many will hunker down in the shade of foliage. Early mornings and evenings are busiest on summer days.
Red breasted sapsucker
5. Some birds will soar at a higher altitude where the air is cooler. They’re still in the sun but air cools significantly with elevation. Raptors and some other birds can easily soar up 5000 feet where the air is 20°F cooler.
Bald eagles soar up to 10,000 feet
You can help in a few ways:
1. Set up birdbaths, misters or fountains. They should be shallow (1-2”) with a rim or objects to stand on. Very important: keep them clean and filled! Dirty water will spread disease. Anyone who has birdbaths knows how quickly they get dirty — birds are bathing after all! And all that splashing empties out a bath in no time. In summer especially birdbaths should be monitored daily. Sometimes I need to refill twice in a day.
The sound of moving water is a magnet to birdies. Of my three birdbaths, the “fountain” gets significantly more traffic than the still ones. It’s brought birds into the yard I didn’t previously see, such as warblers. I’m still playing around with how to set it up best for the birds. Since I can’t dump it out to clean and refill, I treat it regularly with an enzyme mix that breaks down organic debris.
.
2. Landscape your yard with shrubs and trees, which provide a shady refuge in summer for birds to wait out the heat of the day. Avoid pruning and limbing at this season not just to protect nests but to maintain foliage for birds.
House Wren in Twinberry
3. Growing flowering and fruiting plants in your yard provides nearby food so birds don’t have to do as much flying far afield. Birdfeeders help too, although again they must be kept clean so they help more than harm. Choose foods that won’t go bad quickly in the hot sun, or rotate them out.
Red-breasted nuthatch with Black oil sunflower seed
Some sources for more info:
How Do Wild Birds Keep Cool in Summer?
How to Help Birds Beat the Heat
How are you and your local birdies holding up in this summer heat? What’s up in your birdy world lately?
