Green eggs and scam: Cuckoo finch's long con may be up
For two million years African cuckoo finches have been tricking other birds into raising their young by mimicking the colour of their eggs, but new research suggests the tables may be turning in this evolutionary scam.
The cute yellow appearance of the cuckoo finch belies its nefarious nature: it smuggles its forged eggs into foreign nests, where unwitting foster parents treat them like their very own.
The cuckoo finch eggs then hatch a little earlier than the others in the nest, allowing them to grow quicker and beg more loudly for food than the host chicks—which starve to death as their confused parents prioritise the imposter.
Aiming to save their young from this grisly fate, birds like the African tawny-flanked prinia, a common victim of the ruse, have evolved ever more colourful and elaborate patterns for their eggs to avoid falling for counterfeits.
But the wily cuckoo finch has responded in kind, evolving the ability to copy a variety of egg colours and signatures of several different bird species.
Way back in 1933, British geneticist Reginald Punnett hypothesised that cuckoo finches inherited this remarkable talent of mimicry from their mothers.
His theory has been proved for the first time by a study published in the PNAS science journal this week, which confirmed that the skill is inherited via the W chromosome which only female birds have—similar to how only human males have the Y chromosome.
Spot the fake: The egg on the right belongs to the zitting cisticola bird, but the one of the left is a cuckoo finch forgery.