The famous frigatebird is known for being able to fly continuously for weeks or even months, a lot more than other birds that can only do it for a couple of days. They can fly at altitudes of 2,000 feet and quickly go down to sea level. Frigatebirds are a family of seabirds that are mostly found in tropical environments. Most of them have black plumage, and males have a distinctive red pouch, which they use to attract their mates.
It is no wonder that they can fly son high since their bodies are carefully designed for that matter. Their stretched wings can reach up to 7.5 feet long, which would credit Frigatebirds as the birds with the largest wing to body weight ratio of any species.
Flight Duration: Months
But even if they have massive and light wings, it is hard to conceive how these birds can sustain flight for months. Ornithologist Henry Weimerskirch tracked 80 frigatebirds of the Fregata minor species to analyze why they can fly for so long.
Weimerskirch published his study in the journal Science and revealed that frigatebirds could take advantage of the ocean’s air currents, so they can fly for extended periods of time without having to stop to rest. He and his team compared their behavior to that of a roller-coaster, “relying on thermals and winds to soar within a 50- to 600-meter altitude band under cumulus clouds and then glide over kilometers at low energy costs.”
He noted that these birds although they cannot swim, they feed on fish and nothing else. The reason they can’t swim is that their feathers lack the oily protection that allows other birds, such as ducks, not to get soaked when they submerge in water. This allows frigatebirds to be lighter and to, of course, sustain greater and longer flights.
The secret? Air currents
The team tracked the birds using lightweight solar-powered GPS trackers and monitored their heart rate and flight patterns from 2011 to 2016. Some specimens managed to fly for up to 56 days, hovering over hundreds of miles of miles with just one wing flap every six minutes. The air currents managed to lift the birds over two miles into the sky without them having to flap their wings to gain altitude, only to remain balanced.
Weimerskirch claimed that they were able to tell that frigatebirds do this intentionally, and he also noted that it is admirable that these birds can survive thousands of feet above sea level, where oxygen is scarce, and water starts to freeze.
One of the patterns followed by frigatebirds and that the team managed to capture is that these birds tend to remain in the proximity of doldrums. These are zones below the equator where winds are calm. Sailboats are known to be trapped in doldrums because this is when two trade winds meet so that wind currents can disappear completely.
The edges of doldrums are where different air currents merge. In the Indian Ocean, there are many, as the research team noted it. Frigatebirds locate these doldrums and then pass onto the updrafts, and they get lifted miles away in just a couple of minutes. These currents are reliable and are teeming with cumulus clouds, which also tend to indicate the updrafts that can be used by these birds.
Frigatebirds fly trajectories of over 400 miles each day, while looking for food for only a couple hours. This shows that their caloric output is very low, which is fascinating as they can take advantage of natural events to complete impressive flight paths. It was shown that the bird’s heart rate was able to remain at low frequencies when flying at high altitude, just as if it was resting on its nest, proving that they do not “fly,” instead, these birds “glide” and relax their bodies.
Low energy, sustainable and lightweight
Because frigatebirds use much less energy than other birds to reach high altitudes, this may allow for some development in aeronautics. Perhaps taking advantage of wind currents will render lightweight aircraft sustainable for longer and higher flights. The main issue towards a practical end to the frigatebirds’ behavior is that their bodies and wings are very light, which plays a significant role in their flight abilities. The bones of frigatebirds are pneumatic, meaning that they are filled with air. Their bones make up only 5 percent of their body weight. It is also worth noting that, because of their wing to body ratio, frigatebirds have a hard time taking off, which may indicate another reason why they take into surfing air currents for boosting their flight.
The main issue towards a practical end to the frigatebirds’ behavior is that their bodies and wings are very light, which plays a significant role in their flight abilities. The bones of frigatebirds are pneumatic, meaning that they are filled with air. Their bones make up only 5 percent of their body weight. It is also worth noting that, because of their wing to body ratio, frigatebirds have a hard time taking off, which may indicate another reason why they choose to surf air currents for boosting their flight.
Researchers wondered if frigatebirds were able to get any sleep while they were flying, which should be the case, since the longest registered flight of the tracked specimens was an astounding 56 days, practically two months without stopping to rest on earth. We humans still complain about 5 and 6-hour flights, waiting in lines, and about the mediocre in-flight service, while these majestic animals spend days in high altitude without spending energy, nor landing or looking for a mate.
Source: Science