New research shows that the Andean condor is capable of soaring more than 100 mi (160 km) without flapping its wings. The research, led by Professor Emily Shepard of Swansea University and Dr. Sergio Lambertucci of the Universidad Nacional del Comahue in Argentina, indicates that the world's heaviest soaring bird, which weighs up to 15 kg (33 lb), only flaps its wings one percent of the time it's in flight.
For many people, a bird's a bird, but if you conduct a careful study of how they fly, the variety of ways they flap their wings is impressive, to say the least. Birds live in a surprisingly wide range of environments and have occupied ecological niches ranging from those associated with insects to large land-based carnivores. When some fly, they flap their wings continuously to stay in the air, others swoop and glide, and some twist and wheel in bewildering maneuvers as they chase down mosquitoes in the twilight.
Perhaps the most majestic are the soaring birds. These can include ones like the albatross that can cover thousands of miles on their great migrations, and raptors like hawks and eagles that ride on the thermals as they scan the ground and water for some small animal or fish that's been nominated for lunch.
The question is, how does a heavyweight like the Andean condor manage to stay aloft? Found in the Andes mountains along the Pacific coast of South America, the Andean condor is not only heavy, it has a wingspan of almost 3.3 m (11 ft), which is exceeded only by that of four seabirds. However, where the seabirds live by catching fish, the condor feeds on large carrion like deer and cattle that it lives in rough country.
To find out more about how the Andean condor flies, the team used high-tech flight-recorders to track how often the birds flapped their wings or made turns in the air as they searched for food. What it discovered was that 75 percent of all flapping occurred when the condor was taking off. Once airborne, the bird would soar for a long time as it sought out updrafts and rising thermals to help it gain and maintain altitude.
According to the team, one bird managed to go for five hours without flapping as it passed the 100-mile mark.
"Watching birds from kites to eagles fly, you might wonder if they ever flap," says study author Dr. Hannah Williams, now at the Max Planck Institute for Animal Behaviour. "This question is important, because by the time birds are as big as condors, theory tells us they are dependent on soaring to get around. Our results revealed the amount the birds flapped didn’t change substantially with the weather.
"This suggests that decisions about when and where to land are crucial, as not only do condors need to be able to take off again, but unnecessary landings will add significantly to their overall flight costs."
One significant point was that the birds the team studied weren't fully mature, which suggests that these energy-saving techniques of soaring are adapted by the condors even when very young. Aside from taking off, the condors only flapped when their glides between thermals were likely to bring them close to the ground.
"This is a critical time as birds need to find rising air to avoid an unplanned landing," says Lambertucc. "These risks are higher when moving between thermal updrafts. Thermals can behave like lava lamps, with bubbles of air rising intermittently from the ground when the air is warm enough. Birds may therefore arrive in the right place for a thermal, but at the wrong time. This is a nice example of where the behavior of the birds can provide insight into the behavior of the air."
The findings were published in the Proceedings of the National Academy of Sciences.
Source: Swansea University