When Do Birds Soar?
Birds soar by using columns of rising air called thermals to gain altitude without flapping their wings. Thermals form when the sun heats up the earth’s surface, causing the air above it to rise. As this warm air rises, cooler air moves in to take its place, creating an updraft that birds can ride to gain elevation.
Times of Day When Thermals Form
Thermals typically form during the warmer parts of the day when solar radiation is strongest. The most common times for thermal formation are:
- Mid-morning – After the sun has warmed the ground for a few hours, thermals start developing, often peaking around 10-11am.
- Early afternoon – The sun continues heating the earth, creating strong thermals from around 1-4pm.
- Late afternoon – Just before sunset, the ground radiates heat back into the air, causing thermals to redevelop.
Birds will adjust their soaring patterns to take advantage of thermals during these peak heating periods each day.
Weather Conditions for Thermal Formation
Certain weather conditions promote better thermal formation:
- Sunny days – Direct sunlight warms the ground most efficiently.
- Light wind – Gusty winds break up thermals, so light breezes under 10mph are optimal.
- Dry air – Humidity hampers thermal formation, so dry conditions are preferable.
- Flat terrain – Smooth, flat ground heats consistently to create strong thermals.
Birds are most likely to soar on sunny days with clear skies, light winds, and low humidity over flat landscapes like prairies or deserts. Cloudy or rainy days inhibit thermals.
Seasonal Differences in Thermals
The strength and timing of thermals also varies throughout the year:
Season | Thermal Pattern |
---|---|
Summer | Strong, consistent thermals form early and last late in the day due to extended daylight and peak sun angle. |
Spring & Fall | Decent thermals form but may be weaker and more intermittent as temperatures are cooler. |
Winter | Weaker, sporadic thermals form only during the midday peak heating hours on sunny days. |
Soaring conditions are optimal for birds during the summer and much more limited in winter. Some migratory birds rely heavily on summer thermals for long distance travel.
How Birds Use Thermals to Soar
Birds have adapted specialized skills and behaviors to ride thermals efficiently:
- They circle upward in a spiral pattern to stay within the rising column of warm air.
- They adjust their speed, angle of bank, and position to center themselves in the thermal core.
- They spread their wings and feathers to maximize lift.
- They may flap occasionally to gain altitude as needed.
A variety of birds utilize thermalling techniques, including large raptors, storks, pelicans, and some small songbirds like swifts. Birds with larger wingspans can soak up more lift to soar better. Here are some well-known thermal soaring experts:
Turkey Vultures
Turkey vultures are supremely adapted for soaring. They opt to flap only about 1% of flying time, relying on thermals for the other 99%. Their large 6ft wingspan provides substantial lift surface area. Turkey vultures can stay aloft for hours, soaring high and far with barely a flap.
Hawks & Eagles
Many hawks and eagles are expert thermal riders as well. Red-tailed hawks, for example, maximize lift by fanning their tail feathers into a broad, rounded shape while soaring. Large golden eagles and bald eagles can lock their wings straight and drift effortlessly on thermals. Powerful raptors like these only need to flap occasionally to push higher in rising columns of air.
White Pelicans
One might not expect a 9ft wingspan waterbird to be a thermal ace, but pelicans are incredibly proficient soarers. They utilize thermals to traverse vast distances during migration, typically flapping just 20% of flight time. Pelicans fly in orderly lines or V-formations, surfing rising air together for efficiency.
Common Swifts
Unlike most songbirds, swifts have adapted to become expert thermal riders. They have long, curved wings ideal for catching lift. Swifts even sleep while gliding and soaring on thermals and updrafts! During migration, swifts may remain aloft for months, eating, mating, and sleeping all while airborne.
Soaring for Energy Efficiency
Thermalling and soaring provides huge efficiency benefits for birds:
- Gliding burns 10x less energy than flapping flight.
- Riding updrafts allows birds to fly faster and farther.
- Less energy spent on flying means more resources for breeding and raising young.
Birds that rely heavily on soaring like vultures and pelicans would struggle to stay airborne for extended periods without exploiting thermals and wind patterns.
Migrating birds also capitalize on thermals and other helpful wind patterns to travel immense distances. Here are some incredible migration feats powered partially by soaring flight:
Bird | Annual Migration Distance |
---|---|
Arctic Tern | 25,000 miles |
Swainson’s Hawk | 14,000 miles |
Ruby-throated Hummingbird | 2,000 miles |
Without the energy savings from soaring on thermals and other winds, these migrations would be impossible!
Threats to Soaring Birds
Since many birds rely so extensively on updrafts and thermals for energy-efficient travel, threats to these aerial “highways” pose serious risks:
- Wind turbines – Turbine blades can destabilize thermals and create dangerous turbulence.
- Deforestation – Clearing forests disrupts wind patterns and removes thermal triggers like shade and updrafts.
- Urbanization – Buildings and paved surfaces inhibit ground heating and thermal formation.
- Climate change – Shifting weather may alter historical wind patterns and thermal hotspots.
Conservation efforts aimed at protecting soaring bird habitats and migration routes will be critical going forward. Soaring birds serve as important barometers for overall ecosystem health. Their reliance on natural wind phenomena highlights the need to better understand and safeguard these invaluable aerial resources.
Conclusion
To gain lift and elevation without wing flapping, birds utilize columns of rising warm air called thermals that form when the sun heats the earth’s surface. Peak thermal conditions occur on sunny days with light winds and dry air, typically mid-morning to early afternoon. Soaring on thermals allows efficient long-distance travel during migration for many birds like hawks, eagles, pelicans, and swifts that are adapted for gliding flight. As urbanization and climate change threaten to disrupt natural wind patterns, conservation of aerial habitats will be crucial for protecting soaring birds worldwide.