Swifts Fly High on Moonlit Nights

We know that swifts spend a lot of their lives in the air. The common swift, for example, is the record-holder for the longest flight time without landing – a mind-boggling ten months in the air. Now ornithologists have learned that some swifts also fly high, up to three miles high, especially on moonlit nights.

“It’s a completely new discovery,” says Anders Hedenström, an avian ecologist at Lund University and lead author of the research, and he’s not kidding. High altitude flights in sync with the moon’s cycle had never before been observed in birds.

The scientists tagged seven black swifts (Cypseloides niger) with tracking devices and recorded their movements over two years. “We discovered that the black swift does not land a single time during their eight and a half month long migration, so they stay in the air the entire time,” says Hedenström.

The birds flew at low altitudes during the day and ascended to 5,000 feet or so at night. During a full or large moon, the swifts soared up to 13,000 to 16,000 feet above ground. Why they do this remains a mystery. The researchers were lucky enough to monitor the high fliers during a total lunar eclipse, when the birds descended rapidly to lower altitudes in the darkness, then rose again when the moon returned.

Swifts feed on insects when they’re in flight; they even mate and sleep while in the sky. They tend to have higher survival rates than other bird species, possibly because they can avoid predators and parasites by staying above it all.

See the range of the black swift, and hear its call, here: xeno-canto.org/species/Cypseloides-niger.

Photo creditt: Zak Pohlen & Rob Sparks