Hundreds of birds found dead on a road may have been killed trying to escape a bird of prey, police have said.
More than 200 starlings were found dead on Anglesey on 11 December.
One of the birds had a tag from Lithuania, 1,032 miles (1,662 km) from where it was found dead.
North Wales Police’s Rural Crime unit said investigations supported the theory they had hit the ground trying to avoid a predator.
Initial post-mortem examinations by the Animal Plant and Health Agency suggested the starlings had died on impact with the road.
One had a ring on its left leg and was ringed in 2015 Ventes Ragas, Lithuania, making it four years old.
“It’s highly likely the murmuration took avoiding action whilst airborne, from possibly a bird of prey with the rear of the group not pulling up in time and striking the ground,” a tweet from the unit said.
Mystery had surrounded the death of the birds with one starling expert suggesting they could have been disorientated by sun reflected from a wet road.
At the time Dafydd Edwards, whose partner found the birds, said it was as if “they had dropped down dead from the sky”.
The force said it was waiting for further toxicology results before a final theory could be confirmed.