The RSPB is investigating the death of thousands of common migratory birds at sea after fishermen reported seeing hundreds drop from the sky into the waters of England's south coast.
According to the Daily Mail, the fishermen said the birds were seemingly exhausted and disorientated.
One skipper told the conservation charity: 'While fishing about 10 miles south of Portsmouth, we witnessed thousands of garden birds disorientated, land on the sea and most drowning.
'Species included goldcrests, robins, thrushes and blackbirds. The sky was thick with garden birds. I estimate I saw 500 birds die and that was just in our 300-yard sphere.
'On the way home we just saw dead songbirds in the water: it was a harrowing sight.'
It is believed the birds were killed by a combination of fog and heavy winds around the coast at the end of October.
Martin Harper, conservation director of the RSPB, said: 'The scale of these reports are truly shocking, and it has the potential to adversely affect the status of species which may be declining for other reasons.'
At the same time, the east coast, from Northumberland to Kent, has seen perhaps millions of birds arrive, including redwings, fieldfares, bramblings and blackbirds. It is possible that these may have been the lucky survivors that managed to make it across the North Sea from Scandinavia in difficult conditions.
The RSPB said many others may have perished before making the landfall.
Speaking to BBC4's Material World programme, Graham Madge of the RSPB said: 'What we seem to have is what ornithologists call a classic 'fall' where you get a concentrated period of migration that basically dumped a lot of birds along the east coast.
'We think that these birds left Scandinavia in good weather conditions, which is what birds are evolved to do, and they were drifting along the North Sea where they encountered the foggy conditions that we had a few weeks ago.'
Mr Madge said that after the 'fantastic sight' of thousands of birds arriving on the east coast, fishermen along the south coast reported birds dying, just a couple of days later.
'We started receiving reports from fishermen along the south coast ... saying that there boat was surrounded by hundreds of birds many of which were just so tired and disorientated that they dropped into the sea.
'This is particularly unusual; it's birds like thrushes, robins and a whole variety of other species that can be very good long distance migrants.'
The RSPB warns that exhausted birds that have made it to Britain will be looking for food and may visit gardens. It said that now is the time to start topping up bird tables and feeders.
'These birds need all the help they can get, so gardeners and farmers can also help birds by not cutting hedgerows laden with much-needed berries,' said Ian Hayward, of the RSPB's enquiries team.
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