There are certain birds that are ‘household names’: everyone knows them, because their appearance or behaviour is embedded within our childhood memories and cultural history. The robin, for example, with its rosy red uniform, or the striking black and white magpie, forever associated (probably erroneously) with having a fondness for shiny items.

The cuckoo is another of these birds. As they are seldom seen, it’s not their appearance that has won them a coveted place in the national psyche. It can be attributed to two things – their distinctive ‘cuck-coo’ call, and their reputation for treachery during the breeding season.

Cuckoos are summer migrants from Africa and arrive in Britain in late March to early April. Their simple two-note song has for centuries been associated with the arrival of spring, and many a celebrated wordsmith has been inspired by their melodic call.

The cuckoo’s apparent villainy has also secured it a starring role in the works of literature’s great and good: Shakespeare wrote of the bird arousing fear in married men in Love’s Labours Lost. The cuckoo’s seemingly deviant behaviour spawned the word ‘cuckold’, describing the husband of an adulterous wife, which appeared in written form as early as 1250.

It has long been known that after breeding, the female cuckoo searches for a suitable ‘host’ nest in which to lay her eggs and then leaves the parenting of her offspring to the unsuspecting owner. But it was not until more recently, in the nineteenth and twentieth centuries, that the cuckoo’s behaviour, and how it actually managed to get away with it, was more fully understood.

Cuckoos will only lay their eggs in the nests of a particular selection of host birds. In Britain, these are, in 90 per cent of cases, dunnock, reed warblers, meadow pipit, robin and pied wagtail. But in the late nineteenth century, two German ornithologists went further and found that female cuckoos specialise in parasitising only one particular host species. That is, there are a number of different ‘races’, or gentes, of cuckoo – reed warbler specialists, dunnock specialists, and so on.

A century or so later, in the 1980s, two British biologists expanded on this discovery. They found that many cuckoos have evolved to produce eggs that are almost identical in appearance to their host birds to prevent them from being rejected. Thus, a cuckoo that ‘specialises’ in reed warblers will lay a green egg, while a meadow pipit specialist will lay speckled white and brown eggs.

Once a host nest has been located – that is, one that is full of eggs – the female cuckoo will wait until the owner has vacated it and will swoop down, eject an egg, and then lay her own in its place.

The next part of this sophisticated operation is even more incredible. Once the cuckoo chick has hatched, it will expel all the other eggs by levering them out of the nest on its back. If the other eggs hatch before the cuckoo, it will do the same, but with the live chicks rather than the eggs!

After about a fortnight, the cuckoo chick will be many times the size of its adopted parents, and will need feeding almost constantly. Although you’d think the exhausted parents might have realised by this stage that something is amiss, they continue to be deceived by yet another trick. According to Professor Nick Davies, interviewed in the excellent book Say Goodbye to the Cuckoo by Michael McCarthy, the cuckoo chick mimics the sound of a full brood demanding food to spur its frantic ‘parents’ into a food-collecting frenzy.

Perhaps it is the cuckoo’s cunning that has secured it its place in the hearts of the nature-loving public (everyone loves a good villain), or maybe we are uplifted by its seasonal song.

Whatever the reason, one thing that is certain is that since the early 1980s, numbers of these fascinating birds have been steadily falling and they are now a red-listed species of highest conservation concern. The reasons for this dramatic decline are not fully understood, but climate change, habitat loss and a shortage of host birds are all thought to play a part.

The protection of suitable habitat around the UK is vital in supporting the survival of the cuckoo. One place where cuckoos have been recorded in here in Bedfordshire is at our Millennium Country Park site, where reed warblers play unwitting host to their offspring. If you’re out exploring the park this spring listen out for and enjoy the enigmatic song of the cuckoo, which can carry for miles - and try not to think of the mischief that this intriguing species may be about to make!

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