Nenagh Guardian 5th May, 1880 p.2(abridged)
It is a popular belief that we should hear the cuckoo about the 21st of April and that whatever you are doing the first time that you hear the cuckoo, the same you will be doing most frequently through the year. Another belief is that an unmarried person will remain single as many years as the cuckoo utters its call when first heard.
The cuckoo was often celebrated in the medieval poetry of all ages and all languages, and was looked upon as possessing some share of supernatural knowledge. In some parts it seems to have been an article of belief that it was one of the gods who took the form of the bird. It was considered a crime to kill it. Its most singular quality in this superstitious lore was the power it had of telling how long people would live.
The notion which couples the name of the cuckoo with the character of the man whose wife is unfaithful to him appeared to have been derived from the Romans and is first found in the middle ages in France. The opinion that the cuckoo makes no nest of its own, but lays its eggs in that of another bird, who brought up the cuckoo to the detriment of its offspring was well-known to the ancients and is mentioned by Aristotle and Pliny.