Within the seemingly organised and wonderful world of birds, there lurk cheats and baddies; birds that knock the system and get away, not with murder, but without lifting a finger (nor even a wing) to help with the bringing up of their offspring.
These are the brood parasites, the birds that do not make their own nests but simply dump their eggs in another’s nest, knowing full well that the chosen host will be an excellent parent and that their genes will go on into the next generation. For that is the driving natural force – to reproduce.
In the beginning there were no baddies, it was each species for itself, trying to carve its own niche in a not so friendly world. But as things settled down there opened up gaps for the birds with dubious morals; cheating was suddenly a viable way of life. Early brood parasite ancestors must have made their own nests, and by chance an individual laid an egg in another bird’s nest and this chick was successfully reared by the unsuspecting foster parents, and so was born the Bird Mafia. Cuckoos are not the only members of this gang; honeyguides, whydahs and widowfinches are also among their number. Each member has its own preferred host species and devious ways of combating discovery.
Here at the Cavern we have five cuckoo species with the Redchested Cuckoo or Piet-my-vrou being the most vociferous. As with most brood parasites, this large bird chooses a much smaller victim to bring up its kids, most commonly depositing its egg in the nest of the Cape Robin. Robin eggs and nestlings are summarily despatched by the much larger cuckoo chick, and the foster parents work themselves to the bone trying to assuage the hunger of this enormous child. Unlike mammals that become imprinted on whoever they first see at birth, these cuckoos go off into the world believing they are cuckoos and when it comes to singing the right song and choosing the right mate, they seem to get it right. Black, Jacobin, Klaas’s and Diederik Cuckoos are the other Cavern cuckoos, all having different host species.
The frenetic Pintailed Whydah is another of this gang. The cheeky black and white “King-of-Six” leads his wives to the nest of the enchanting Common Waxbill. In this case the whydah chick is reared alongside the waxbills, no murderous tendencies here. The Black Widowfinch chooses Bluebilled Firefinches as its favoured host.
The honeyguides, of which we have three species recorded in the Cavern grounds, have a different strategy. They use hole-nesting birds such as the Blackcollared Barbet to rear their children. In the darkness of a nest hole there is no need to match the egg to the host’s egg, but the danger lies in first getting the egg into the hole, and second when the young honeyguide is ready to leave. Fully grown and in adult plumage, it runs the risk of being recognised by the barbets as an undesirable, and mob justice can be harsh.