Conned by a Cuckoo

By Philippa Hadlow

Reading time: 12 minutes

In 1940, Theodor Geisel, AKA Dr Seuss, created Mayzie, the lazy bird who tricked Horton the Elephant into sitting on her nest.

In Horton Hatches the Egg, Mayzie takes a sneaky trip to balmy Palm Beach while Horton is left to keep her egg warm until hatch day. Horton’s adamant he’s up for the job: “An elephant’s faithful, one hundred percent.”

I wonder if Dr Seuss’ inspiration came from the cuckoo. Like Mayzie, cuckoo birds are notoriously deceptive. It’s no wonder the term “cuckold” came about to describe the human translation of that trickery. The Old French 13th-century adaptation of the word refers to the illicit affair of a married woman. Her liaison results in the birth of a child that her cuckolded husband raises as his own. A typical cuckold will go through life blissfully unaware that his dear offspring is, in fact, that of a stranger.

By Philippa Hadlow

Reading time: 12 minutes

In 1940, Theodor Geisel, AKA Dr Seuss, created Mayzie, the lazy bird who tricked Horton the Elephant into sitting on her nest.

In Horton Hatches the Egg, Mayzie takes a sneaky trip to balmy Palm Beach while Horton is left to keep her egg warm until hatch day. Horton’s adamant he’s up for the job: “An elephant’s faithful, one hundred percent.”

I wonder if Dr Seuss’ inspiration came from the cuckoo. Like Mayzie, cuckoo birds are notoriously deceptive. It’s no wonder the term “cuckold” came about to describe the human translation of that trickery. The Old French 13th-century adaptation of the word refers to the illicit affair of a married woman. Her liaison results in the birth of a child that her cuckolded husband raises as his own. A typical cuckold will go through life blissfully unaware that his dear offspring is, in fact, that of a stranger.

While you might think a cuckold lives in “cloud-cuckoo-land” (first coined in The Birds, by Aristophanes, 414 BC) and is just a bit “cuckoo” (first literary reference to being crazy in My Man Jeeves, P. G. Wodehouse, 1919), the avian version is anything but. In fact, of 150 species of cuckoo, around 60 are members of the Cuculinae subfamily and indulge in clever trickery of their own. They are known as brood parasites and lay eggs in other birds’ nests for these (mostly) hospitable birds to incubate, hatch, and raise.

Cuckoos have been practising nest bullying tactics for centuries and have them down to a fine, evolutionary art. The cuckoo has evolved to know which host best provides security and care of her offspring in a process called natal philopatry or habitat imprinting. This term refers to the cuckoo’s ability to recognise the phenotypes of host nests and distinguish them from those of another potential host species. She will then return to the same area (natal territory) to continue breeding year after year.

Her actions are not just parasitic; they are callous. Once a female cuckoo has scoped out a suitable host nest, she will invade it, pull the host bird off and whip in to lay her egg. If there are already host eggs or chicks in the nest, she will eject at least one or destroy the lot before laying her own. To avoid detection, her eggs have evolved to mimic the colour and pattern of the favoured host’s eggs – which all have different species-specific designs. Replicating the unique colours of those is one tactic; producing a ‘cryptic’ egg that is darker and easier to hide in the nest is another.

Cuckoo eggs have also developed a tougher, heavier shell to withstand host rejection should it occur, and to increase the chances of damaging resident eggs when dropped from above. And because the female cuckoo holds her egg in her oviduct for an extra 24 hours, it requires less incubation once laid, offering the advantage of early hatching. This gives the parasitic nestling an opportunity for a final coup d’état.

Hoping for a feed

The un-feathered and still-blind baby cuckoo unceremoniously hoists the competing eggs onto its back and levers them over the side of the nest. Its naked wings take on an almost prehensile facility and act as tools in the quest, and its determination to get those eggs out of the nest is incredible to watch. Any host chicks who managed to avoid the ‘mother’ cuckoo’s negative attention when she laid her egg, or have since hatched may now suffer at the wings of the cuckoo chick. Smug, it can now sit and bask, open-beaked, in the devoted attention of its adopted family. The sight of a grotesquely-large cuckoo chick teetering on the tip of a wee nest and being pandered to by its tiny, exhausted foster parents is both comical and tragic.

For years, naturalists struggled to accept the idea that the cuckoo indulged in such unseemly behaviour. Early scientists were outraged at the thought and in 1787 when the originator of vaccination, Edward Jenner, produced a paper describing an accurate account of what happens to the unfortunate young of the parent bird in whose nest a cuckoo deposits her egg, he was booed by the Council of the Royal Society. Jenner’s claims were still not entirely believed until the artist Jemima Blackburn, a keen observer of birdlife, saw a blind nestling pushing out a host’s egg. Her description and illustration of this in 1871 were enough to convince Charles Darwin to revise a sixth edition of On the Origin of Species.

However, even until the early 20th century, there was speculation as to the validity of the cuckoo’s parasitical habits. A myth persisted that it laid its egg either on a stump, the barrel of a prone tree or on the leafy ground, then took the egg in its bill or claws and put it manually into the nest.

In 1918, a businessman-cum ornithologist by the name of Edgar Chance decided to take things into his own hands. His short film The Cuckoo’s Secret was the first wildlife documentary ever made and proved, without a doubt, that the mother cuckoo did indeed dart into her host’s nest to lay her egg, and that the subsequent cuckoo fledgling tossed its fellow host mates over the brink.

The costly side effects are serious if not fatal to those that succumb to the cuckoo’s gambit. Diminished numbers of their own kind due to egg ousting, nestling slaughter, heavy competition between survivors, and host bird nest abandonment ultimately means less of that species.

But it’s not all plain sailing for the cuckoo, either. Some host birds are more colour sensitive than others and, canny with it, will reject the imposter cuckoo egg. In this case, the spurned female cuckoo, in a furious fit of revenge, may destroy the remaining host eggs. Occasionally, other zealous cuckoos will do a quick flyby, spot a cuckoo egg in a host nest, and flick it out to be replaced with one of their own. Mostly, however, although the unexpected addition to the clutch and subsequent hatchling is a little on the chunky size, the conned host will generally keep the peace and question not. In their book Parasitic birds and their hosts: Studies in coevolution, 1998, Rothstein & Robinson call this adaptive acceptance “evolution lag”.

While species of Old World (African, European, and Asian) cuckoo have evolved to epitomise successful brood parasitism, its relatives in the Antipodes are equally adept. Found throughout Australasia, Indonesia, Papua New Guinea, Solomon Islands and Vanuatu, the shining bronze-cuckoo (Chrysococcyx lucidus) and the long-tailed cuckoo (Eudynamys taitensis) make their presence known in New Zealand from around October. Arriving home from a South-West Pacific winter (unlike Mayzie, Palm Beach is not a port of call), they are the only New Zealand bush birds to migrate.

While the name cuckoo is derived from Old French “cocu” as a transcription of the bird’s call, the shining cuckoo or pīpīwharauroa has no such onomatopoeic association. As a harbinger of spring, her distinctive song is keenly awaited by both ornithophiles and those weary of winter.

Ka tangi te wharauroa, ko nga karere a Mahuru,” says the Māori proverb: “If the shining cuckoo cries, it is the messenger of Spring”. That cry is worth waiting for, too – heavenly, with the first notes an upwardly-slurred repetitive and wistful whistle followed by a pause and a sweetly melancholic downwards end. Her song is enough to make you forgive all her selfish vagrancies.

She’s also rather beautiful, with an iridescent golden-green feathered back, white cheeks, and a sportily-striped breast and underbelly. True to cuckoo form, rather than waste time and effort building her own nest, she instead lays her incongruously large egg in the shadowy nest of a grey warbler (Gerygone igata) or Māori riroriro. Fifty-five percent of grey warbler nests are targeted as host birds (Davies, Nick, 2010), yet at this point, its population holds steady at a “not threatened” status.

 

The cuckoo’s egg dwarfs the warbler’s by a notable two millimetres. The female warbler possibly raises a feathered eyebrow at her prowess in producing such a beauty but is unable and uninterested in checking its provenance. And so, while there’s a sizeable size difference between Horton the Elephant and a grey warbler, the two aren’t without similarities; just like Horton and unwilling to express disloyalty, the warbler accepts the giant egg as one of her own.

The grey warbler, weighing in at only six grams compared to the 23-gram cuckoo, has her work cut out once the egg is hatched. Before that time, she’s busy gathering resources for the arduous task of cuckoo rearing ahead. Unlike her own offspring, who are independent at 28 days – if they manage to stay in the nest – it’s a 40-day haul before this fraud is ready to leave.

You might wonder about the parent imprint and potential identity crisis the baby cuckoo faces without a genetic, same-species role model to emulate. The cuckoo has evolved to counter that particular problem as well, using phenotype matching and a password-like vocal trigger that unlocks learning of species-specific cues at their first encounter with a conspecific (same species) (Hauber et al. 2000, 2001).

However, how does the young adult cuckoo know where to migrate once he is fully-fledged? Without cuckoo parents as leaders, he must somehow figure out when and where to take flight and navigate up to 5000 miles overseas to his ancestral wintering abode in the Solomon’s, guided only by an innate migration programme.

The shining cuckoo managed to come 56th in Forest and Bird’s annual Bird of the Year competition in 2018, pipping the aquatic scaup by five points. Open to international voting, the competition has encountered scandalous vote-rigging and humorous controversy from all quarters, this year no less than others with the appointment of – not a bird – but a bat as the winner. Perhaps for 2022, it’s the precocious pīpīwharauroa’s time to shine.

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