Cuckoos infiltrate the nests of other birds with similar-looking eggs, but drongos have evolved a highly effective way to snuff out the imposters. Their ability to recognise the uniquely patterned marks of their own eggs, like a signature, means they may reject up to 94 per cent of cuckoo eggs. Instead of caring for their own offspring, African cuckoos (Cuculus gularis) lay a single egg in the nests of fork-tailed drongos (Dicrurus adsimilis), tossing out a drongo egg to match the original clutch count. If the young cuckoo is adopted and hatches, it immediately pushes out the remaining drongo eggs to become its hosts' only charge. Jess Lund at the University of Cape Town, South Africa, and her colleagues gathered 192 eggs – including 26 that had been laid by cuckoos – from fork-tailed drongo nests in the forests of southern Zambia.