Birds chirping outside your window one day and gone the next when a heatwave hits? If you’ve noticed your feathered friends seem to vanish when temperatures soar, you’re not alone. Many backyard birdwatchers and nature lovers have pondered this phenomenon.
Read on to discover the reasons behind the disappearing acts of birds in hot weather.
Birds Migrate to Cooler Areas
Some Species Have Innate Migration Instincts
Many bird species possess an incredible innate ability to migrate long distances to escape intense heat. Research shows that birds can sense changes in day length, which triggers hormonal changes that stimulate their internal navigation systems.
Some species, like the Arctic tern, make mind-blowing round-trip migrations of over 40,000 miles annually – all because their biology compels them to pursue more comfortable temperatures!
Birds Follow Food Sources
Birds also migrate to locate vital food and nesting resources. As temperatures rise in their breeding areas, the plants and insects they rely on start to disappear. Rather than face potential starvation, resourceful birds travel to habitats where nourishment is plentiful.
For example, ruby-throated hummingbirds make a 2,000 mile journey from Canada to Central America to follow flower blooms that sustain their high-energy lifestyles.
Hot Spells Trigger Early Migrations
Typically, migration is initiated by seasonal cues. However, extremely high temperatures have been known to spur earlier than normal migratory movements. During hot spells, birds become stressed and instinctively seek relief.
A 2021 Audubon report found that ideal migration conditions occur when temperatures range between 60-84°F. Unfortunately, climate change models predict intensifying heat waves, indicating birds may be forced to migrate sooner and over longer distances in the future.
Birds Find Shelter and Shade
Midday Heat Drives Birds to Shade
When the midday sun beats down, birds will seek out shade and shelter to escape the intense heat. Many birds cannot tolerate prolonged exposure to high temperatures, as their bodies are not designed to dissipate heat effectively. Seeking shade is an important survival strategy on hot, sunny days.
Tree canopies offer an oasis of shade that provides welcome relief from the blazing sun. Birds will flock to trees to rest under their leafy branches during the hottest part of the day. The difference in temperature between the sun and the shade can be as much as 20-30 degrees Fahrenheit.
What a respite for a tiny bird! They can pant to cool down as they take a break from foraging.
In addition to trees, birds will use any structure or object that casts a shadow for shade. Bushes, cactuses, and manmade structures like porches or even park benches are fair game as a shady spot. Birds have even been seen spreading out their wings and holding them over their heads, using their own bodies as shade umbrellas!
Birds Use Tree Canopy for Relief
Birds rely heavily on trees for shade and shelter from intense midday heat. The leafy canopy of dense trees provides invaluable respite from the blazing sun. Under a tree’s umbrella of foliage, the temperature can be reduced by up to 20 degrees compared to unshaded areas.
Small birds like chickadees and nuthatches will gather together in flocks under the cool shade of trees during peak heat. Warblers and tanagers also seek shelter among the rustling leaves when the sun is at its zenith.
The trees’ layered branches diffuse the harsh sunlight, allowing these birds a chance to rest and recuperate.
In hot climates like deserts and chaparral ecosystems, the shade of trees can mean the difference between life and death for birds during extreme heat waves. Specific shade trees like the palo verde and mesquite trees act as critical oases for birds like cactus wrens and curve-billed thrashers when desert temperatures skyrocket over 110°F.
Birds Seek Shelter in Underground Burrows
Some clever birds have figured out how to escape the intense midday heat by sheltering in underground burrows and cavities. Burrowing owls, for example, take over prairie dog burrows and other rodent holes to ride out scorching summer days in subterranean coolness.
The burrow acts as a natural air-conditioned refuge that maintains a stable, cool temperature even when outside conditions turn infernal. While the desert surface bakes under the blazing sun, the temperature just a few feet underground hovers around a comfortable 60-70°F. What a perfect hideaway!
Other birds like kingfishers and bank swallows dig their own burrows into dirt cliffs and embankments near water. These self-made bunkers offer protection not just from heat, but also from predators and storms.
Even roosting communally in large numbers, bank swallows can keep their burrows a balmy 84°F when outside temperatures soar over 100°F in the blistering sun.
Birds Adjust Behaviors to Deal with Heat
Altering Feeding Patterns and Habits
When the mercury rises, birds will often adjust their feeding patterns and habits to deal with the heat. Many species will start to forage earlier in the morning or later in the evening when temperatures are cooler.
For example, hummingbirds typically feed most actively in the early morning and late afternoon during hot summer days. Some birds may also expand their diet during heat waves, consuming more juicy fruits or insects with higher water content to meet their hydration needs.
Species that eat seeds or nuts may switch to consuming more greens, buds, and berries as well. According to research from the Cornell Lab of Ornithology, American goldfinches increase their consumption of plant sources of water by up to 50% during periods of extreme heat.
Changing Nesting Locations
Birds have some ability to adjust where they nest during periods of hot weather. Tree and cavity nesting species may move to shadier, cooler areas. According to a 2017 article from Audubon Magazine, one study of mountain bluebird boxes found that bluebirds chose cooler north-facing nest boxes over warmer south-facing ones once temperatures rose over 77°F.
Some open nesting birds may add more insulation to their nests or choose nest sites that offer more shade from the sun. One study found that pied flycatchers built nests with more insulating materials during hot years.
Birds may also begin nesting earlier than usual to allow young birds to leave the nest before peak summer heat arrives.
Engaging in Heat Dissipation Activities
When the mercury climbs, birds rely on specialized behaviors to release excess body heat and avoid overheating. Panting is one common heat dissipation technique, increasing evaporation. Some species, like mourning doves, have special blood vessels in their wings called rete mirabile that facilitate heat loss when the wings are extended.
According to the Audubon article, birds may hold their wings away from their bodies to aid cooling by evaporation. Seeking shade and bathing frequently in water can also help birds dump excess heat. Interestingly, a 2020 study found that some birds living in hot, arid environments allow their body temperatures to rise significantly during the daytime, then lower their temperatures at night – possibly an adaptation to conserve water.
Extreme Heat Can Be Deadly for Birds
Rising temperatures brought on by climate change pose a severe threat to many species of birds. Extreme heat events can quickly take a devastating toll on both migratory and non-migratory bird populations if they cannot find reprieve.
Heat Stress Takes a Toll
Prolonged exposure to sweltering temperatures can overwhelm birds’ ability to thermoregulate. When core body temperatures rise past sustainable levels, irreparable cellular damage and death can occur. Smaller birds are particularly susceptible as they must work harder to stay cool.
Birds primarily regulate their temperature through respiratory evaporation and panting. However, these cooling mechanisms become ineffective past critical heat indexes. Seeking shade provides minimal relief on extremely hot days.
Without access to water for bathing and rehydration, fatal overheating can happen rapidly.
Dehydration is a Major Threat
The loss of bodily fluids through accelerated respiration, panting, and defecation poses another life-threatening risk. Studies show dehydration directly intensifies the impacts of heat stress on avian physiology.
As climate change alters precipitation patterns, drought conditions are becoming more widespread. Reduced water availability further compounds the dangers hotter temperatures present to birds. Species dependent on ephemeral desert water sources are especially imperiled when hot spells desiccate the landscape.
Heat Impacts Reproduction and Offspring
Beyond direct mortality dangers, extreme temperatures also threaten birds’ reproductive capacity. Exposure to intense heat can damage egg cells and decrease sperm counts. Nestlings and hatched chicks are also highly vulnerable to overheating and dehydration.
Hotter seasonal norms are already linked to smaller clutch sizes, higher infertility rates, and more frequent abandonment of nests. Continued warming could devastate future generations. Studies project multiple common species face extinction by 2100 if adaptation measures falter.
With heatwaves intensifying due to climate change, birds will likely continue struggling through warmer breeding seasons and summers. Providing more shade, nest boxes, and access to water can help counteract some hazards.
But curbing emissions remains imperative to give wild avian populations a fighting chance.
Conclusion
In summary, birds tend to disappear in sweltering temperatures due to innate migration patterns, seeking shelter and shade, adjusting behaviors to deal with heat, and the direct impacts of extreme heat on avian physiology.
Understanding why our feathered friends temporarily vacate their usual habitats can help bird lovers support backyard birds during weather extremes. Providing fresh water, shade sources, and native plants with seeds and fruits birds rely on can help ensure they return when more normal temperatures prevail.
