The pomarine jaeger was believed to be the only one of its species on Pelican Island, which is around 15kms from the far-north Queensland coast, before it became a snack.

Pomarine jaegers breed in the Arctic but migrate across the globe.

While the species is found in Australia, they typically stick to the more southern areas on the eastern coast.

Department of Environment, Science and Innovation senior ranger Lee Hess said they had been monitoring the crocodile's behaviour as it was also new to the island.

"We were lucky enough to take photos and videos of the crocodile as it crawled from the ocean, but what we didn't know is it set its sights on the bird," Mr Hess said.

"I'm not sure if [the pomarine jaeger] had ever seen a crocodile before and wasn't attuned to the danger.

"Unfortunately it was a long way to fly to end up like this."

It's believed this is the first recorded interaction between a pomarine jaeger and an estuarine crocodile.