By Megan Shersby

Published: Thursday, 12 May 2022 at 12:00 am

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The common cuckoo, also known as the European cuckoo, is a remarkable and fascinating bird, migrating to the UK from Africa every spring. It’s famous for its parasitic behaviour, which is specifically brood parasitism where it does not build its own nest and raise its young, but instead tricks another bird species into doing the work for it.

Such behaviours have inspired various cultural and social references. William Shakespeare refers to the cuckoo in spring, and to cuckoldry, in Love’s Labours Lost, and the cuckoo’s call inspired the cuckoo clock.

The ‘cuckoo’ name has been used in other species’ names, referencing the parasitic behaviour. The cuckooflower (Cardamine pratensis), also known as lady’s smock, is so-called as it begins to flower when cuckoos begin to call. Queen cuckoo bumblebees usurp the nest of another bumblebee species, killing the other queen and forcing the workers to look after her young instead. The term cuckoo bee is also applied to other bee species that exhibit kleptoparasitic behaviour; laying their eggs in the nests of other bee species. In the UK, the most noticeable species are the Nomada bees, which are wasp-like in appearance and typically lay their eggs in the nests of mining bees (Andrena).

BBC Wildlife‘s Megan Shersby spoke to cuckoo expert Professor Nick Davies for an episode of the BBC Countryfile podcast. In the episode, they took a walk around the National Trust’s Wicken Fen Nature Reserve to look for reed warbler nests, listen out for cuckoos and discuss Nick’s research into the species’ behaviour.

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What is the scientific name of the cuckoo?

The scientific name of the common cuckoo, also known as the European cuckoo, is Cuculus canorus.

There are four subspecies of the common cuckoo: C. c. canorus, C. c. bakeri, C. c. bangsi and C. c. subtelephonus. 

With each subspecies, there are distinct races, which specialise in the type of host bird species that they target and the colour of the egg that they lay.

The Cuculus genus contains 11 extant species of cuckoo, including the African cuckoo (Cuculus gularis), Indian cuckoo (Cuculus micropterus) and red-chested cuckoo (Cuculus solitarius). The genus is part of the wider cuckoo family (Cuculidae).

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How to identify cuckoos

Cuckoos have a grey-blue back, head and chest, with white and dark barred underparts. Females have some pinkish-buff colouration on their chest and neck. Both males and females have a yellow ring around their eyes, a yellow base of the bill and yellow feet.

An individual can measure between 32 and 34cm in length, with a wingspan between 55 to 65cm in length and weighing between 105 and 130g.

There is a rufous (reddish-brown) colour morph.

A cuckoo can be confused with a sparrowhawk (pictured below), and in flight, with a kestrel. Studies comparing the reaction of reed warblers to taxidermy models of cuckoos and sparrowhawks found that the warblers were more aggressive to cuckoos that have their barred underparts obscured. This suggests that the cuckoo’s barring is an evolved mimicry of the sparrowhawks’ barring.

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Do both male and female cuckoos call ‘cuckoo’?

Male cuckoos deliver the familiar ‘cuck-oo’ note, used to advertise their presence on the breeding grounds to potential mates and other males.

Territorial males will call repeatedly throughout the day. The first note is higher and louder than the second, the difference between them has been described as a perfect descending minor third.

Being loners that parasitise the social systems of other species, cuckoos have less need than most birds for complex vocal communication. But they do have a little more to say than just “cuckoo.”

Only the males make the iconic two-syllable call, which is mostly deployed in competition with rivals. But they also have a three-syllable version – “cuck- cuckoo” – which seems to have more to do with attracting mate, or, if excited, a rapid ‘gowk gowk gowk’.

Females themselves produce a bubbling chuckle, ‘kwik-kwik- kwik’. This has long been suspected to mimic sparrowhawks in order to scare host species from their nests before the cuckoo lays her parasitic egg. But it also seems to be associated with the male’s three-syllable call, suggesting that both are involved in sexual communication.

This question originally appeared in BBC Wildlife, and was answered by Stuart Blackman and by Mike Toms.

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Which nests do cuckoos lay their eggs in?

Cuckoos are brood parasites, which means that they do not actually raise their own eggs. Instead, they will sneak onto another bird’s nest and lay an egg in that nest.

Female cuckoos target the nests of specific bird species. In the UK, this is usually the reed warbler, the dunnock and the meadow pipit.

On the European continent, other bird species may also be targeted, such as the European robin, garden warbler, pied wagtail and common redstart.

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How do cuckoos trick their host bird?

You might think that the female host bird, be it a robin, dunnock, or reed warbler, would spot the imposter cuckoo egg. Sometimes she does, and she uses her beak to put a hole through the shell and then ejects the egg out of the nest. But surprisingly often, that’s not the case. And there’s a number of reasons for why the cuckoo egg doesn’t get clocked as an imposter and remains in place.

When the female cuckoo visits the nest to lay her egg, she will also remove one of the host’s eggs within the nest (she may even eat the host’s egg). Thus, when the female host returns, she will have exactly the same number of eggs. The cuckoo’s visit to the nest is also very quick, to reduce the chance of being spotted by the host, and she is only there for about 10 seconds.

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