The cuckoo - a remarkable creature
- Green Fingers
- Jun 8
- 14 min read
Introduction
I had intended to write about dormice, but then a cuckoo appeared. I was busy brush-cutting pathways through the bracken on my land, to give my young trees room to breathe. Yet, over the harsh rasp of the brush-cutter, I heard the cuckoo call. Cumbrian cuckoos are very noisy. When I formerly lived in the south of the UK, I was lucky to hear a cuckoo call more than twice before it fell silent. In Cumbria, the cuckoos appear more assertive. They call, and they call, and they call. There is no stopping a Cumbrian cuckoo.
The Common Cuckoo (Cuculus canorus) is one of the most recognisable birds in the British Isles and across Eurasia and is celebrated for its distinctive two-note song and unique reproductive strategy. It has captivated attention for centuries, evoking mystery and admiration in equal measure. Its call is often the harbinger of spring. Cuckoos migrate from the UK to the savannahs of tropical Africa for the winter months. That is a very long way. The shortest distance between London and a tropical African country such as Ghana or Nigeria is around 4800 kilometres (3000 miles). The distance to South Africa, which is at the southern edge of tropical Africa, is significantly longer, at around 9600 kilometres (6000 miles). Cuckoos migrate huge distances.
Adult cuckoos typically leave the UK in June, while fledglings follow later in the year. They return to the UK in late March or early April. Their numbers are a worry. In the late 20th and early 21st centuries, cuckoo numbers declined dramatically by 37%, so the bird is on the official (red) list of the UK’s most threatened species[i]. It has been on that list for more than a decade[ii].
Yet the cuckoo is more than a seasonal marker. It is an ecological specialist and evolutionary marvel. Its significance lies not only in its role as a brood parasite - more to follow - but in its broader contributions to understanding coevolution, ecological health, and cultural identity.
Brood Parasitism: An Evolutionary Strategy
The cuckoo is renowned for a breeding strategy that has fascinated scientists for more than a century. The bird is a brood parasite. Instead of building nests or rearing its own young, female cuckoos lay their eggs in the nests of other species, typically small passerines. A passerine is any bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an anisodactyl arrangement of their toes - three pointing forward and one back - which simplifies perching.
Once laid, the egg is incubated by the unsuspecting host. When hatched, the cuckoo chick instinctively ejects the host’s eggs or nestlings and monopolises the parental care of its foster species, whatever that may be. While this may appear ruthless, it is a highly effective survival strategy.
Brood parasitism is a subclass of parasitism and is a behavioural pattern of animals that rely on others to raise their young. It can be observed in particular species of birds, insects, and fish. For example, brood parasitism can be shown by the Common Moorhen (Gallinula chloropus), the Eurasian Teal (Anas crecca), the European Bitterling (Rhodeus amarus), and even some bumblebees (Bombis vestalis). A brood parasite manipulates a host, either of the same or another species, to raise its young as if it were its own, for birds usually using egg mimicry, with eggs that resemble those of the host[iii]. Brood parasitism has independently evolved in multiple avian families, but the cuckoo exemplifies one of the most sophisticated iterations. The female cuckoo carefully observes potential host nests, often mimicking the behaviour of predators or non-threatening birds to reduce suspicion while laying her egg. The egg is usually deposited within seconds, thereby driving stealth and efficiency[iv].
In European cuckoos, multiple female lineages are adapted to parasitise specific hosts. The bird lays eggs that resemble those of its target species, such as the Reed Warbler (Acrocephalus scirpaceus), Marsh Warbler (Acrocephalus palustris), or Meadow Pipit (Anthus pratensis)[v]. Cuckoo chicks are often larger and more demanding than host chicks. They exhibit exaggerated gaping displays and begging calls. Research has shown that these begging calls are acoustically matched to simulate a brood of multiple chicks, which stimulates increased feeding by the host parents[vi]. This acoustic mimicry, rather than visual resemblance, is sometimes more important in maintaining the parasitic relationship[vii]. Remarkable.
Host-Parasite Coevolution
The relationship between the cuckoo and its hosts is one of the most compelling examples of coevolution in the natural world. Host species face significant reproductive costs from parasitism and have developed a range of responses to minimise these impacts.
For example, a host may evolve egg discrimination abilities, rejecting eggs that differ from their own in shape, size, or pattern. In response, cuckoos improve their mimicry, further entrenching the cycle of adaptation and counter-adaptation[viii]. Some host species, such as the Great Reed Warbler (Acrocephalus arundinaceus), are particularly adept at spotting foreign eggs, while others, like the Dunnock (Prunella modularis), show little or no recognition.
Nest vigilance is another defensive strategy. Hosts may build dome-shaped nests with narrow entrances to prevent cuckoo access or guard their nests more frequently during laying periods. Aggressive mobbing of adult cuckoos is also common. Some birds even abandon parasitised nests altogether and opt to rebuild elsewhere. There is also local variation in egg rejection rates, depending on the prevalence of cuckoo parasitism in the area. This well demonstrates how evolutionary pressure is distributed unevenly across landscapes[ix].
Cultural Significance
The cuckoo occupies a unique place in the human imagination. For centuries, it has been a potent symbol in folklore, poetry, art, and music. Its call is arguably one of the most recognised in Europe and traditionally heralds the arrival of spring. This first hearing is still celebrated in rural traditions across many parts of the world. In some cultures, the direction of the cuckoo’s call is said to foretell fortune or misfortune, wealth or poverty, and even longevity.
1. Celtic and Irish Traditions
In Celtic mythology, the cuckoo is associated with the transition between worlds and is often linked to themes of death and rebirth. The bird's call was believed to summon the dead, and its appearance was considered an omen of change. In Irish folklore, the cuckoo heralds the arrival of summer, not so much spring, and its call has been used in various superstitions to predict longevity and fortune. For instance, hearing the cuckoo while holding money was thought to bring wealth[x].
2. Anglo-Saxon Literature
The cuckoo appears in Old English literature, notably in the Exeter Book Riddles[xi], where it was depicted as a mysterious and solitary figure. The riddle reflected the bird's enigmatic nature and its association with isolation and longing.
3. Greek and Roman Mythology
In Greek mythology, the cuckoo is linked to Hera, the goddess of marriage. Zeus, seeking to win Hera's affection, transformed himself into a cuckoo during a storm and sought refuge in her arms, leading to their union[xii]. The bird's association with spring and renewal is also evident in the Greek proverb, "One cuckoo does not make a spring," and highlights its role as a seasonal marker[xiii].
4. Indian Mythology
In Indian tradition, the cuckoo is sacred to Kamadeva, the god of love and desire. Its melodious call is associated with the onset of spring and the subsequent monsoon season and symbolises fertility and renewal.
The Jacobin cuckoo (Clamator jacobinus), which is different to the Eurasian cuckoo (Cuculus canorus ), is found in Africa and Asia, but is still a member of the cuckoo order of birds. It is partially migratory and, in India, has been considered a harbinger of the monsoon rains because of the timing of its arrival. In Indian mythology and poetry, it is known as the chātaka and is represented as a bird with a beak on its head that waits for the rains to quench its thirst[xiv]. It thus symbolises longing and unfulfilled desire.
5. Japanese Folklore
In Japan, where the Lesser Cuckoo (Cuculus poliocephalus) can be found, the bird is called hototogisu and is associated with melancholy and unrequited love. Its call is believed to represent the longing of the dead to return to the world of the living. The bird also features prominently in Japanese poetry and art. It frequently symbolises the transient nature of life and the sorrow of separation[xv].
6. African Traditions
In various African cultures, the cuckoo is associated with the arrival of the rainy season and is regarded as a symbol of fertility and abundance. Its call is interpreted as a sign of impending rain, essential for agriculture and food provision.
7. Russia
Among the Mari people of Russia, the cuckoo holds a significant place in folklore, being associated with death and the afterlife. The bird is believed to be a messenger from the spirit world, and its call is used in divination practices to predict events such as marriage and longevity[xvi].
8. British folklore
In British folklore, the cuckoo is a trickster figure, admired for its cleverness but also viewed with suspicion. Its parasitic habits have led to its association with infidelity and deceit. Here it is in Shakespeare’s Love’s Labour’s Lost:
When daisies pied, and violets blue,
And lady-smocks all silver-white,
And cuckoo-buds of yellow hue
Do paint the meadows with delight,
The cuckoo then, on every tree,
Mocks married men, for thus sings he:
'Cuckoo! Cuckoo, cuckoo!'
O word of fear,
Unpleasing to a married ear[xvii].
Symbolism and Interpretations
The cuckoo has an extensive symbolism that is interpreted in different ways. For example:
1. Harbinger of Spring
Across many cultures, the cuckoo is regarded as a herald of spring. Its arrival and distinctive call signal the end of winter and the beginning of a new season, symbolising renewal and hope.
2. Symbol of Deception
The cuckoo's brood parasitism, where it lays eggs in the nests of other birds, has led to its association with deceit and unfaithfulness. This behaviour has influenced language and literature, with terms such as cuckold deriving from the bird's name.
3. Emblem of Longing and Melancholy
In many traditions, the cuckoo embodies themes of longing, sorrow, and unfulfilled desire. Its solitary nature and haunting call evoke feelings of melancholy, thereby making it a powerful symbol in poetry and art.
The bird’s symbolism extends into music and literature. On Hearing the First Cuckoo in Springis a tone poem composed in 1912 by Frederick Delius[xviii]. It was first performed in Leipzig on 23 October 1913. The piece opens with a slow three-bar sequence. Its first theme is an exchange of cuckoo calls, first for oboe, then for divided strings. The second theme is scored for first violins, and is taken from a Norwegian folk song, In Ola Valley. The clarinet returns with the cuckoo calls before the piece ends. I have listened to the piece multiple times, and even I can hear the cuckoo. Do give it a go.
Meanwhile, it is not only Shakespeare but poets such as Wordsworth[xix] and John Clare[xx] have also written evocatively about the cuckoo. They noted its fleeting presence and mysterious life cycle.
The Cuckoo’s Name
The cuckoo’s name has been given to plenty of things. These include:
1. Cuckoo Flower (Cardamine pratensis)
The cuckoo flower, also known as lady’s smock, is a common wildflower that blooms in spring in damp meadows across the British Isles. The association with the cuckoo arises from the flower's flowering period, which coincides with the first calls of the male cuckoo, typically in April[xxi].
In folklore, the cuckoo flower is regarded as a symbol of the renewal of life after winter. However, in some traditions, particularly in northern England, it was considered unlucky to pick the flower, possibly because of its association with fertility and maidenhood[xxii].
2. Cuckoo Spit
Cuckoo spit refers to the frothy white substance found on the stems of plants in spring and early summer. This foam is produced by the nymphs of froghoppers (Cercopoidea) and is a protective habitat[xxiii]. The term cuckoo spit arises not from any relation to the bird itself, but because it appears during the same seasonal window as the cuckoo’s return.
Traditional beliefs attributed cuckoo spit to the bird directly or saw it as a sign of impending rain or the presence of spirits. While these associations lack empirical support, they persist in regional lore[xxiv].
3. Cuckoo Pint (Arum maculatum)
Cuckoo pint, also known as lords-and-ladies, is a woodland plant with a striking spathe and spadix, often interpreted symbolically as phallic. The name “pint” is thought to be derived from the Middle English pyntel, meaning penis[xxv]. The prefix “cuckoo” again likely refers to the plant's appearance in spring.
This plant has a strong presence in folk traditions linked to fertility, sexuality, and taboo. It was sometimes used in ancient rites, though its toxic sap made it dangerous to handle. The plant’s many vulgar folk names, including dead man’s fingers and parson-in-the-pulpit, reflect its sensual symbolism[xxvi].
4. Cuckoo Bee
The term cuckoo bee is applied to species of bees, such as those in the genus Nomada, which do not build nests of their own but instead lay their eggs in the nests of other bee species. The analogy with the cuckoo’s parasitism is well documented in the entomological literature[xxvii].
5. Cuckoo Wrasse (Labrus mixtus)
The cuckoo wrasse is a brightly coloured fish found in North Atlantic waters. The origin of the name is unclear, but it is possibly a reference to the fish’s colourful appearance, metaphorically linking it with the exoticism often associated with the cuckoo[xxviii]. There are no strong mythological connections, but it reflects the bird’s association with the peculiar.
6. Cuckoo Clock
The cuckoo clock, which originated in the Black Forest region of Germany in the 18th century, incorporates a mechanical cuckoo that appears at regular intervals to mark the time. It is a cultural object rather than a naturally occurring phenomenon but plays on the widespread recognition of the cuckoo’s call as a measure of seasonal change[xxix].
7. Cuckoo Land
Cuckoo land is an idiom that signifies fancifulness, delusion, or unreality - “they are in cloud cuckoo land”. It derives from a medieval tradition, particularly from the fictional land of Cucania, where cuckoos were thought to sing all year[xxx].
8. Cuckoo’s Nest
Cuckoo’s nest also entered popular language as a term for a place of madness or a psychiatric institution. It was famously used in Ken Kesey’s One Flew Over the Cuckoo’s Nest[xxxi]. The link to madness probably stems from the use of “cuckoo” as a colloquial synonym for insanity, which was already in use by the 16th century[xxxii].
Conservation and Environmental Indicators
Beyond cultural and evolutionary interest, the Common Cuckoo has significant ecological importance. As a migratory species that relies on a complex network of habitats and host species, the cuckoo is particularly vulnerable to environmental changes. This is likely why it has suffered serious population declines, especially in the United Kingdom.
Habitat loss, changes in agricultural practices, and declining populations of host species are among the primary causes of these declines. Because the cuckoo is so intricately linked to its hosts, any factor that affects host abundance or distribution can have cascading effects on cuckoo populations. In this sense, the cuckoo serves as an umbrella species for monitoring ecosystem health.
Climate change has further complicated the picture. Migratory birds, including the cuckoo, have changed their arrival and departure times from and to their various lands of origin. This desynchronises their breeding cycles with those of their host species. This mismatch reduces the success of parasitism and leads to further population pressures[xxxiii].
Studies have found that cuckoos tend to thrive in areas of high avian biodiversity. Their presence is often positively correlated with overall bird richness, suggesting that protecting cuckoo habitat can benefit a wider array of species. This makes the cuckoo a valuable indicator species, guiding conservation efforts in fragmented and changing landscapes[xxxiv].
Citizen science projects, such as the British Trust for Ornithology’s “Cuckoo Tracking Project”, have provided invaluable data on cuckoo migration routes and behaviour. These studies have also revealed that British cuckoos spend their winters primarily in Central Africa and follow distinct migratory corridors. Conservation strategies must therefore be international in scope, and encompass breeding grounds, stopover sites, and wintering habitats[xxxv].
For the future, and indeed for the present, these are hugely essential studies. I have no desire to lose the cuckoo.
***
References
[i] Birds of Conservation Concern 5. https://www.bto.org/sites/default/files/publications/bocc-5-a5-4pp-single-pages.pdf. Accessed 1 June 2025.
[ii] Heart of England Forest. Can you clock a cuckoo? 9 April 2019. See https://heartofenglandforest.org/news/can-you-clock-cuckoo#:~:text=A%20changing%20world,journey%20before%20crossing%20the%20desert.. Accessed 1 June 2025.
[iii] Wikipedia. See https://en.wikipedia.org/wiki/Brood_parasitism. Accessed 1 June 2025.
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[xviii] YouTube. Frederik Delius – On Hearing the First Cuckoo in Spring. https://www.youtube.com/watch?v=3xHIhcstxUM. Accessed 4 June 2025.
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