paper published in Current Biology examines the extinction of a colourful little bird which, until recently, thrived in the eastern US. With the appalling environmental catastrophe enveloping Australia, home to 56 of the world’s 370 parrot species, this account of the Carolina parakeet’s demise is timely.
Parrots don’t like the northern hemisphere. We have no native ones in Europe, which seems odd, considering that the introduced rose-ringed parakeet took to European cities like a fish to water. Imported as pets, some of these glamorous birds escaped, or were deliberately released.
Against the odds, they survived; rose-rings are living wild from the south of England to the Iberian Peninsula and eastwards to Greece and Turkey. There are large populations in the Netherlands, Belgium and Germany. Noisy conspicuous creatures, they have not so far reached Ireland.
The US until recently had two native parrots. Both were exterminated, not by the people living beside them for millennia, but by the Europeans who overran the country. About 1,700 American thick-billed parrots, classified as ‘endangered’ by the International Union for Conservation of Nature, survive in Mexico.
The other former US resident, the Carolina parakeet, is extinct everywhere. Noisy flocks used to live in the east of the country. In 1832, John J Audubon warned numbers were declining. None was seen in the wild since 1910. Inca, the last member of his race, died in Cincinnati Zoo in 1918. His mate, Lady Jane, had died a year earlier. The pair lived in the cage that housed the world’s last passenger-pigeon, another victim of human greed and ignorance. However, what caused the parakeet’s demise? This green-and-blue-plumaged bird, with an orange-red head and a long tail, was hunted during the 19th century; its feathers were used to decorate hats. Exploitation and habitat destruction would have reduced its numbers but should not have caused complete extinction. Persecuted creatures become scarce and marginalised but usually manage to hang on somewhere. Other factors must have been at play here.
A Vienna University team, using a stuffed specimen from a private collection, have managed to sequence the Carolina’s DNA and compare it to the genome of its nearest living relative, the sun parakeet of South America. As a population declines, individuals breed closer to their kin. This leads to progressively less genetic variation between the chromosomes inherited from fathers and those from mothers. However, the Vienna analysis showed that no such convergence in the Carolina parakeet’s case. Its population, therefore, had not encountered bottlenecks during the three million years of separation from the sun parakeet, nor had the species declined gradually into extinction.
The bird must have suffered some sort of catastrophe. A disease imported with poultry might, for instance, have been responsible. Is the fire disaster in Australia having similar effects on vulnerable creatures there?
There is a glimmer of hope for the Carolina parakeet; it has been listed as a ‘Lazarus’ species, a possible candidate for de-extinction. As with the passenger pigeon and the mammoth this is a very long shot.
Pere Gelabert et al. ‘Evolutionary History, Genomic Adaptation to Toxic Diet, and Extinction of the Carolina Parakeet’; Current Biology, January 2020