International Cuckoo Day: Common Cuckoo

The 20th April 2026 is International Cuckoo Day. To mark this, and the 350th anniversary of the publication of Francis Willughby’s Ornithologia, this post will focus on part of the description of the Common Cuckoo in Ornithologia.

Willughby knew this bird by the name of Cuckow or Cuculus. In 1758, Linnaeus gave it the taxonomical binominal name of Cuculus canorus, which remains its modern name.

The Cuckoo in Francis Willughby's Ornithologia

In Ornithologia, the Cuckoo’s length was given as 12 inches from the tip of the bill to the end of the tail. It was described that the feet were yellow. The upper mandible of the bill was somewhat hooked and longer than the lower. For the most part, the upper side was of a dark or blackish colour, whilst the underside was a pale or whitish yellow. It was written that the irises of the eyes were of a hazel colour, not yellow as Ulisse Aldrovandi had written. However, it is now known that juveniles have dark brown eyes that become yellow when they reach adulthood. In Ornithologia, it was also written that the edges of the eyelids were yellow. The nostrils were round, wide, and raised above the surface of the bill. Willughby commented that he had not seen another bird with nostrils like this. Today, the elevated nostrils are considered a characteristic identification feature of all the species of the Cuckoo family.

Juvenile Cuckoo, 2024, by Andrey Gulivanov, CC-BY-SA 2.0, via Wikimedia Commons

In Ornithologia, it was written that the throat, breast, and belly were white, with transverse dark lines, which were not interrupted. The black lines were thicker upon the throat, and had less white between them. The feathers of the head were of a dark brown colour with white edges. On the head were one or two white spots. The feathers on the middle of the neck and back, and also the long scapular feathers, were brown with a tincture of red and whitish edges. Today, it is known that all of these aspects of the feathers clearly identify the bird they examined as a juvenile. It was also written in Ornithologia that the rump was ash coloured. Today, it is known that as the juvenile ages the brown-red colour of the juvenile plumage will gradually change to a grey colour.

There were 19 flight feathers in the wings, the larger of which were blacker. The interior vanes of the outermost had long, transverse, white spots and the tips of all were white. All from the second had their exterior vanes spotted with red. Today, these red spots are known to be a feature of juvenile plumage. The covert feathers of the wings were of the same colour with those on the back, but the outermost were darker.

It ate caterpillars and other insects.

Further Reading: John Ray, Francis Willughby's Ornithologia, 1678, p.97, T10.

Carl Linnaeus, Systema Naturae, 10th edition, p.110-1.

Author - Debbie Jordan, Middleton Hall Volunteer.

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