A transcription of the intertitles doubles as a synopsis:

The Cuckoo has excited the attention of naturalists since Aristotle (B.C. 384). Various theories have been advanced as to its habits but it remained for Mr. Edgar Chance to obtain direct evidence on points which have baffled observers for thousands of years.

The Cuckoo returns to England every Spring from Africa, where she spends the winter. The female shirks the duties of a mother bird by depositing her eggs one at a time in the nests of other birds - her 'dupes'.

She prefers to get her eggs hatched, and her offspring reared, by the same species of foster-bird as that by which she herself was reared. This Cuckoo's dupes were Meadow Pipits, commonly called Titlarks, here seen at their nest on the ground.

Four years close study of a particular Cuckoo by Mr. Edgar Chance, member of the British Ornithologists Club, enabled him to foretell accurately when she would lay each egg and exactly which nest she would select to receive it.

In his place of concealment, Mr. Chance was able to watch the useless protests of the Titlarks on the arrival of the Cuckoo.

Having selected her dupes the Cuckoo sits motionless on a tree, sometimes for hours, concentrating on her intended victims. At the critical moment for laying the egg she glides down to the nest...

...takes one of the titlark's eggs in her beak, sits on the nest for a few seconds to lay, then flies off to an adjacent tree to eat the stolen egg. N.B. These are the only occasions on record a cuckoo has been photographed in the act of laying.

Trouble for a second home. Forty-eight hours later she lays in another nest. In 1920, this cuckoo laid 21 eggs, the greatest number ever recorded.

Two more days and nights have passed and the cuckoo again slips down to lay in a third nest, to the distress of the helpless owners. In eight seconds the egg is laid.

Not yet three days old and still blind, the young cuckoo ejects from the nest any unhatched eggs by working them with his wings, one at a time, into a hollow in his back and pushing them over the edge.

He next attempts to eject the young tit-larks in the same manner, but is interrupted by the return of the mother.

Not realising the tragedy so narrowly averted, and with no apparent alarm at the dangerous position of her offspring, the mother settles down contentedly.

When again alone, the young Cuckoo puts forth a mighty effort, and after an exhausting struggle ejects his foster brothers from the nest.

The mother returns, and, with an amazing inability to realise what has happened to her babies, and the death that speedily awaits them, feeds them for the last time and settles down to tend the usurper.

Nine days later the young cuckoo, in sole possession and receiving all the tit-bits, has outgrown the nest.

Three weeks old. The youngster is ready to fly, but is still carefully nursed by the tit-larks. They are very particular about removing the ordure which is encased in a white wrapping.

The pugnacity and fearlessness displayed by so young a bird are remarkable.

Mother on baby's back... Though now ready to start in life the usurper still demands to be fed.

The work completed, Mr. Chance is congratulated on his unique achievement. He has secured, for the first time, a record of the Cuckoo laying, and also added many new facts to our knowledge of the Life History of the Cuckoo.

You can read the whole story at your leisure in Mr Chance's book:- 'THE CUCKOO'S SECRET' published by SIDGWICK & JACKSON LTD., 3 Adam St, London. W.C.2.