Tomorrow is Cuckoo Day, when folklore says the first call of the cuckoo is heard, at least in Sussex where a traditional Cuckoo Fair is held in the town of Heathfield. The arrival of cuckoos then gradually moves northwards, with the first sighting in Yorkshire traditionally on April 21. Much depends on the weather, though, as Thomas Hardy wrote in Weathers in 1922:
“This is the weather the cuckoo likes,/ And so do I;/ When showers betumble the chestnut spikes,/ And nestlings fly;”
Over the past 50 years, cuckoo populations have declined across Europe by about a quarter and up to 76 per cent in the UK. Cuckoos spend winter in rainforests in central Africa before taking a perilous journey to the UK and Europe in spring to breed. Before crossing the desert, the birds stop off in west Africa during the rainy season, where they can feast on a cornucopia of insects and other invertebrates ready for the rest of the migration.
Once the cuckoos arrive on our shores, they need to breed and lay their eggs in the nests of unsuspecting birds that unwittingly care for the cuckoo eggs and chicks as their own. But these surrogate birds are breeding earlier as springtimes grow warmer, and a recent study revealed the dilemma facing the migrating cuckoos. Either they set off from west Africa early but without having eaten enough food to survive the long migration to the UK, making them more likely to die before reaching their destination. Or they leave west Africa later, arrive in the UK too late and find their hosts have already fled their nests.
Birds heading to Europe have a slightly shorter migration flight and may be better able to survive on less food during an early migration. But if cuckoos leave west Africa later, they are less likely to find nests in the UK to lay their eggs in. Some cuckoos are now compensating for a late arrival by targeting later-breeding species such as the reed warbler in England.
