A West Midlands businessman with a passion for part-time bird watching uncovered key clues about the predatory cuckoo in an early nature film.
The work of Edgar Chance during the 1920s is featured in Cuckoo, a film for the BBC's Natural World series to be screened on Friday.
The documentary uses archive footage and new photography to explore how European cuckoos manage to lay their eggs in the nests of other birds - who then feed the mighty chicks as their own.
Mr Chance carried out "meticulous preparatory studies" at Pound Green Common in Worcestershire, filmmaker Mike Birkhead said.
He then employed Oliver Pike, a wildlife film pioneer, to capture the cuckoo's activities in what the British Film Institute said was the first film to show a cuckoo laying an egg in a nest.
David Noble, principal ecologist for monitoring with the British Trust for Ornithology, said Mr Chance demonstrated how the cuckoo's "timing was critical".
"There was a lot of speculation and some ideas had been around about the cuckoo's behaviour, but he took the first photographs," he said.
The cuckoo chick usually grows bigger than its adopted parents
The bird dupes her victims by laying only one egg in each nest - and at a time which allows the chick to hatch at the same time as the resident brood, to ensure it gets fed.
Mr Noble, who studied cuckoos for his PHD, said the chicks instinctively pushed eggs and other chicks out of the nests.
He said: "They are fascinating to ornithologists because of what they get away with. They never raise their own young and, because of how they have evolved, they never see their real parents."
He said there were many interesting aspects, such as why the foster parents continued to feed a bird which could be "five times as big" as themselves.
Prof Nick Davies, a zoologist at Cambridge University , told the programme Mr Chance achieved "some brilliant observations" and showed for the first time how a cuckoo laid her eggs.
Children helped Edgar Chance by watching nests in Pound Green Common
"Egg collectors in the 19th Century knew that cuckoos could lay a variety of egg colours and that those colours tended to match the host they chose as a victim," he said.
"Nobody really knew how the cuckoo laid its egg [until] and in what, I think, is one of the greatest bird watchings ever done - Edgar Chance."
Mr Chance asked local children to watch nests around Pound Green Common so he could work out the ones the cuckoo was most likely to visit next. Then Mr Pike was able to position his cameras to catch the best shots.
Mr Chance was from the family that founded the Chance and Hunt glass-making and chemicals firm in Oldbury, West Midlands.
Chance and Hunt said he was its manager between World War I and World War II.
Chance and Hunt, which is now based in Runcorn, Cheshire, said its former boss became known as Cuckoo Chance because of his pioneering research.
Scientists have been intrigued as to why the host birds are duped
He even named his daughter Cardamine - the Latin name for cuckoo flower.
Mr Chance was also an expert on birds' eggs and was considered to have one of the best collections in the country at a time when the hobby was deemed acceptable. In 1954 it became illegal to take birds' eggs from the wild.
He aimed to gather the highest number of eggs from a single cuckoo in one season, Mike Birkhead Associates said. And achieved his aim with a haul of 25 eggs in 1922 with Cuckoo A - the star of Oliver Pike's film.
Gwyneth Jones, of the Pound Green Commoners' Association which looks after the common, said Mr Chance probably came to the Worcestershire green to escape city life.
"I suspect like many people from Birmingham he came out here for holidays," she said.
She said the 52-acre common was still popular for bird watchers and cuckoos were still seen.
But the cuckoo traditionally parasitized on meadow pipits on the common which had largely gone because of overgrowth, she said.
Mrs Jones, who lives in a cottage on the common once owned by her grandfather, said the land had been restored over the past 10 years.
"We hope the clearing of a lot of bracken and re-seeding of heather will bring back ground-nesting birds as well as more cuckoos," she added.
Cuckoo with be screened on BBC Two at 2000 GMT on Friday 9 January
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