Birds have a variety of strategies for dealing with hot weather. Their main priority is preventing overheating, but they also need access to food and water sources. The specific actions a bird takes to stay comfortable in the heat depends on the species and individual circumstances.
Finding Shade and Cooler Areas
One of the simplest things birds do is seek out cooler microclimates. Shaded areas, whether from trees, buildings, or other structures, give birds respite from the blazing sun. Birds may also frequent cooler areas near sources of water, like ponds, streams, puddles, and bird baths. Wetlands, lakeshores, and coastlines tend to be cooler than open fields due to the cooling effect of the water.
Some birds, like vultures, urubus, gulls, pelicans and cormorants, have bare areas of skin on their heads and necks. This allows them to dissipate heat more efficiently. The blood vessels in the skin of their necks bring heat from their bodies to the surface where the naked skin promotes heat loss.
Altering Behavior and Activity
Many species adjust their general activity levels on hot days to conserve energy and moisture. They may spend more time perched or roosting quietly in shady spots. Birds tend to limit unnecessary flight and foraging during the hottest parts of the day, having quick bursts of activity in the cooler morning and evening hours. Hot temperatures may suppress territorial displays, courtship activities, and loud vocalizations.
Some birds practice heat avoidance by migrating to cooler climates, heading north or to higher elevations. Numerous North American songbirds and shorebirds migrate north to breed during the warmer months. Hummingbirds in Southwestern deserts migrate to higher mountain elevations for the summer.
Respiration and Panting
Unlike humans, birds do not have sweat glands all over their bodies to cool down with perspiration. However, they can still use evaporation to lower their body temperature through a process called gular fluttering or panting. Many species, especially large ones like vultures, pelicans, and storks, flutter the tissues of their throat and mouth to increase air circulation and evaporative cooling.
Changing Perches and Nest Sites
Some birds may move their nesting sites to cooler areas, rebuilding nests in shadier spots or closer to water. Birds that nest in tree cavities and enclosed nest boxes can overheat, so they may switch to more open, breezy nests during hot weather. Birds that build hanging nests often orient the entrance downwards in hot climates so rising heat can escape instead of becoming trapped inside.
Altering Nesting Times and Habits
Hot temperatures can lead birds to adjust their breeding chronology and habitat choices. Desert species in the southwestern U.S. tend to nest earlier in the year to avoid the harshest heat. Some birds may have shorter incubation and nestling periods in hot weather to get offspring fledged before conditions become severe. Parents may modify brooding postures to reduce contact with eggs and nestlings during the heat of the day, then resume close contact at cooler times.
Wetting Feathers and Skin
Birds keep themselves cool by wetting their feathers and bare skin patches. Splashing in water sources helps transfer moisture for evaporative cooling. Some species, like storks, herons, and ibises, may defecate on their legs to wet their skin with a cooling layer of moisture. Pelicans, cormorants, and some raptors wet their bellies and breast feathers by wing-flagging, holding damp wings away from their bodies to maximize air circulation.
Changing Foraging Strategies and Diet
Extreme heat often reduces insect activity levels, a food source many birds rely on. Birds may expand their foraging ranges and consume different prey in hot weather. Seed-eating birds are better adapted to heat since seeds remain available even when insects are scarce. Some birds switch their diet to eat more fruits and nectar, which contain more moisture. Hummingbirds get most of their hydration needs from flower nectar.
Efficient Kidney Function
Birds have highly efficient kidneys that allow them to conserve moisture in their urine and feces. Their kidneys recover water and electrolytes from urine before excretion, producing a hyperosmotic urine that requires less water. Birds’ feces consists of a combination of urine and solid waste in the form of uric acid, which allows additional water conservation compared to mammals.
Other Physiological Adaptations
Some desert bird species, like sandgrouse, can absorb water directly through their skin and feathers from pools and damp surroundings. Being lightweight allows birds to become airborne quickly to move into cooler conditions. Many hot climate species have higher metabolic rates, which generates more internal heat, but allows them to dump heat faster when ambient temperatures drop.
Drinking More Water
Accessing adequate drinking water is one of the most critical survival needs for birds in hot weather. Species living in arid environments get a large proportion of their daily water intake from food and metabolic water. But most birds must also drink regularly when it is extremely hot. Providing clean, fresh drinking water helps birds avoid dangerous dehydration.
Heat Stress and Mortality
If birds cannot cool down adequately through their various adaptations, they may suffer from potentially fatal heat stress. Severe heat waves can cause catastrophic mass mortality events, especially for vulnerable species like waterfowl, shorebirds, and colonial nesting birds. Providing shaded, moist conditions is the best way to reduce heat deaths during extreme heat.
Conclusion
Birds have an impressive array of behavioral and physiological adaptations to deal with hot weather and prevent overheating. Seeking shade, minimizing activity, panting, wetting their feathers, adjusting nest sites and habitats, shifting foraging patterns, and drinking more water are some of the key strategies birds use to stay cool. Understanding how birds respond to high temperatures can help us support their survival during heat waves and extreme heat events exacerbated by climate change.