Abstract
The author observed on the egg-laying by Cuckoo Cuculus canolus in the nest of the foster-parents the Bull-headed Shrike Lanius bucephalus, at 11th June 1977, in Shiojiri city central Honshu. The results obtained were as follows;
1) The female Cuckoo deposited her egg directly in the nest of the foster-parents.
2) It took only two seconds to deposit her egg there.
3) The egg was laid at 17:41.
4) The author did not observe that the female Cuckoo took away the eggs of the foster-parents.
5) It was observed that the pair of the Cuckoo might cooperate each other in the egg-laying.
