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Drowning has emerged as a common cause of death for young starlingsAndy Mason/BTO

Scientists are baffled as to why young common starlings have been drowning in groups. Wild birds die relatively rarely from drowning, and usually only in single cases. However, starlings have been spotted having drowned in groups of 10 or more on at least 12 occasions between 1993 and 2013.

Dr Becki Lawson, lead author of the study published in Scientific Reports, commented: "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."

Researchers found all of the incidents took place in spring and early summer and there was no underlying cause of death. "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, in order to better understand why," Lawson said.

Rob Robinson, co-author of the paper published in Nature and Associate Director of Research at the British Trust for Ornithology (BTO), added: "Starlings are a Red-listed species in the UK, under threat from issues including loss of nesting sites and a lack of insect food sources - so much so that their population has declined 79% in the past 25 years. Whilst drowning is an unexpected cause of death, it's not thought to be a conservation threat as - fortunately - these incidents are currently relatively rare.

"However, 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."

Although the experts are saying that providing water sources for wild birds in one's garden is still recommended, they implore the public to add a sloping exit or ramp to water features for an easy exit.