More than 200 starlings found dead on a road in Anglesey may have taken "avoiding action", possibly from a bird of prey, and then failed to pull up in time, say police.
Officers from North Wales Police's rural crime team initially said the deaths were a mystery, following the discovery near Llyn Llywenan in Bodedern on December 10.
Most of the starlings were found on a 100-metre stretch of the road, with others on a nearby hedgerow, but none in the surrounding fields.
Police called in the Government's Animal and Plant Health Agency to examine some of the birds, and say initial post-mortem results showed they had severe internal trauma from impact.
Announcing the findings on its Twitter page, Rob Taylor, team manager at the rural crime team, said: " Please bear in mind that the full toxicology has not been received, so a final theory cannot be confirmed, but we are quite sure of the reasons and cause of deaths to the birds.
"The trauma supports the case that the birds died from impact with the road.
"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.
"We still await toxicology, but from speaking to many people, looking at the injuries and previous worldwide cases, it appears by taking avoiding flight action the murmuration has flown towards the ground and pulled up, but some have not made it.
"Thank you to the many calls and emails we received on this case from around the world.
"Some theories were truly incredible and out of this world. We can only work on hard evidence, previous cases and professional opinion."