Cases of mass-drownings by thirsty starlings have prompted a warning to bird lovers from scientists.
Garden owners with ponds or bird baths were urged to add sloping exits or ramps to water features to avoid more accidental tragedies.
Drowning is rare among birds and when it does occur normally involves individuals rather than groups of animals.
But a new British study of 12 drowning incidents involving starlings between 1993 and 2013 found that on ten occasions more than ten birds died together.
Most victims were young inexperienced birds just a few months old, and all the deaths occurred during the spring and early summer. In every case there was no evidence of underlying fatal disease.
Lead researcher Dr Becki Lawson, a wildlife vet at the Zoological Society of London (ZSL) said: “Drowning appears to be a more common cause of death amongst younger birds, as they may be inexperienced in identifying water hazards. This combined with the fact that starlings are a highly social species could potentially explain why multiple birds drown together.
“Members of the public from around Great Britain have been instrumental in bringing this unexpected cause of starling mortality to our attention by reporting these incidents.
“With starling numbers declining in general across the UK, we need to learn more about how and where these phenomena happen.”
Starlings are a threatened “red-listed” species in the UK, largely because of loss of nesting sites and insect food sources.
In the past 25 years, the UK population has declined by 79 per cent, according to Rob Robinson, study co-author and associate director of research at the British Trust for Ornithology.
He added: “We still need to better understand factors such as disease that might be contributing to this decline.
“We would therefore ask people to keep up the good work by reporting incidents of starling death, whatever the apparent cause, via the Garden Wildlife Health website.” Writing in the journal Scientific Reports, the researchers described the starling drowning incidents as “striking”.
It was possible the birds were mistaking bodies of water as solid surfaces, they said. Most of the drownings involved still water which may look solid as it reflected light.