Another Life: Evolutionary trick that has other birds working for the cuckoo
Science calls it ‘brood parasitism’. The naturalist and ornithologist Gilbert White, with more feeling, called it ‘a monstrous outrage on maternal affection’
Deception: the cuckoo lays its eggs in another bird’s nest. Illustration: Michael Viney
A farmer friend once showed me how to summon a cuckoo from the sky. As its call chimed tirelessly from beyond the trees around his house he spat on the palm of one hand, then cupped them both and brought them to his lips. He blew, as into a trumpet, his fingers uncurling to shape the notes. The bird duly appeared above our heads, its door chime pausing in the vain search for a rival.
My friend, sadly, has now passed, so such a folk skill may have disappeared with him, along with the many Irish names he knew for his fields. The cuckoo, too, is in apparent decline. It may already be here from Africa, ahead of the traditional influx nearer the end of the month, but, erratic as ever in its timing and travelling, its presence now warrants the first attempt at counting.
Don’t tell me, please, that you’ve heard the cuckoo. Instead, send a record online to the North’s Centre for Environmental Data and Recording, which will share it with the Republic’s biological records centre in Waterford. The website, habitas.org.uk/ records/submit-cuckoo-record, asks for the habitat the cuckoo was in, and obviously needs to be sure that you weren’t hearing the collared dove, with its similar call.
In Britain, where numbers of cuckoos have halved in 20 years, at least one of its many mysteries – its migration routes to and from Africa – is beginning to yield to technology. Since 2011 the British Trust for Ornithology has been attaching solar-powered satellite-tracking devices to cuckoos summering in East Anglia, Scotland and Wales. Many have subsequently gone missing in action, perhaps in unseasonal hailstorms or in the spreading expanse of the Sahara, but enough have survived to show the birds making U-turns to find more food, and taking very different routes across the Mediterranean to wintering grounds in the Congo and elsewhere. You can follow the travels this year of nine surviving birds at bto.org/science/migration/tracking-studies/ cuckoo-tracking.
More than enough mystery remains, however, in the details of what science calls “brood parasitism” and Gilbert White, with more feeling, termed “a monstrous outrage on maternal affection”. That the cuckoo lays its egg in a small bird’s nest to get the host parents to feed and rear its big, ugly chick is common knowledge. Not so widely known is the chick’s incredible behaviour in emptying the nest of all the competition.