Scientists say that common swifts can apparently fly around the world for as long as 10 months straight in a year.

As part of a new study, researchers from Lund University in Sweden monitored the birds' flight activity using tracking devices and followed their migratory routes from Sweden to Central Africa.

The birds come to the ground during breeding season in Sweden. However, scientists observed how more than 99 percent of the swifts spent the rest of the 10 months of the year constantly flying. Some birds may dwell on the ground for some period. However, once they learn how to fly, most of them remain suspended in flight.

During the day, the birds can conserve energy by using warm air currents to help them fly, making this the lowest flight activity in a day.

How do these birds sleep? It is still unclear to scientists how swifts catch any rest, let alone sleep. However, they suggest that they can fall into slumber during long and slow descents during flight, especially during dawn and dusk.

 According to the lead author of the study, Anders Hedenstrom of Lund University, common swifts leave their breeding grounds in August to migrate to Central Africa's rainforests via a West Africa route. They never touch the ground until they return for breeding season, which is about 10 months later.

Some of the birds may roost for a brief period during the night in the middle of winter but some never landed on the ground during this time, Hedenstrom said.

Scientists say the distance that these swifts fly during their entire life spans is equal to several round trips to the moon.

Apart from this remarkable life spent mid-air flying around the world, swifts also have longer life spans compared to other bird species. There are recorded individuals reaching the ripe old age of 20.

To date, scientists say that no other bird species can match the swift, even if some remain in flight for a few months.

This new study was published in the journal Current Biology.