[Article déjà publié le 31 mars 2024]
Birds are endurance animals capable of withstanding prolonged physical effort to cover long distances by flying. Wild species are obviously more accustomed to flying than domestic species.
Among these birds, migratory species are those that can fly the furthest for the longest time. However, these animals do not migrate for pleasure, but to survive. When they no longer find enough food in winter, they move towards warmer horizons where food is more abundant.
Such a journey is obviously taxing for the birds and not all individuals arrive at their destination. Those who succeed must then find food to recover their strength and prepare to migrate in the other direction when spring arrives.
Researchers followed around ten swifts during their migration
The swift holds the world record for the longest flight without landing once. Welsh ornithologist Ronald Lockley first suggested it in the 1970s. However, it took a few decades before other researchers confirmed this theory in 2016.
Researchers from Lund University in Sweden published their study in the journal Current Biology. They tested Ronald Lockley’s theory by following 13 adult black swifts during their migration.
The birds were equipped with accelerometers and tiny data loggers that monitored their flight activity. Light level sensors made it possible to locate birds.
The researchers were thus able to follow several birds for several years. They migrated from Sweden to the south of the Sahara at the beginning of winter. The study results confirmed that swifts spend much of their time in the air.
10 months to fly, this is the record held by the swift
Specifically, the monitored birds only spent two regular months on Earth. They take advantage of this period to settle down, reproduce and incubate their eggs. Nonetheless, the swifts spent the remaining 10 months flying.
Researchers estimate that the birds studied spent more than 99.5% of their time flying. Some still landed a few times for short periods during these 10 months.
Three of the swifts studied remained in the air during the 10 months of their migration. They therefore demonstrate excellent physical endurance even though they weigh only 40 grams on average.
Migratory birds that land occasionally do not have the same feathers as long-haulers
Finally, the researchers were able to differentiate between long-haulers and those who landed more regularly by observing their feathers. Birds that occasionally landed did not molt their flight feathers.
Flight feathers are the larger wings that point outward and backward on the wing. On the contrary, the birds that flew without stopping had all molted and therefore had new flight feathers.
To explain this incredible phenomenon, the researchers point out that “black swifts have evolved to become highly efficient flyers, with streamlined body shapes and long, narrow wings, generating lift force at low cost.”
Migratory swifts feed by crunching insects in mid-flight. Researchers also believe they are capable of sleeping while gliding, probably while descending.
Source : Current Biology
