The blackpoll warbler accomplishes a mighty big feat for such a little bird.

Scientists documented how this songbird that weighs 12g completes an arduous non-stop flight over the Atlantic Ocean from forests in New England and eastern Canada to Caribbean islands as it migrates each autumn towards its South American wintering grounds.

By placing miniature backpacks with geolocators on the birds, the researchers determined they flew an average of nearly 2,540km over two to three days.

“No other bird this size migrates for this long in one go. It is truly one of the most amazing migratory feats ever recorded,” said ecologist Ryan Norris of the University of Guelph in Ontario, describing “a fly-or-die journey”.

They landed in Puerto Rico and Hispaniola, resting for a couple of days to a couple of weeks before flying to Colombia and Venezuela.

The spring return flight follows a predominantly overland route through Florida and up the US East Coast.

The research resolves a half-century mystery about blackpoll warbler migration. There had been indirect evidence they were performing this transoceanic migration – for example, blackpolls landing on ships in the Atlantic under bad weather conditions.

But could they really complete such a journey considering a water landing would kill them?

“Some doubted that such a herculean flight would be physiologically and physically possible for a songbird weighing 12g,” said Vermont Cente for Ecostudies ornithologist Chris Rimmer.

Blackpolls, with 20cm wingspans, have distinctive yellow legs and are speckled with black, white and grey feathers with two white wing stripes, a white chin and cheeks, and a black ‘cap’ atop the head.

Before migrating, they gorge themselves to build strength and shrink many of their digestive organs to minimise any part of the anatomy not needed during an extended flight.

The research appears in the journal Biology Letters.