New genetic research conducted by scientists from Griffith University in Nathan, Australia, and the Natural History Museum in Tring, UK, has confirmed that the mysterious, now-extinct bird known as the Spotted Green Pigeon (Caloenas maculata) is a separate species and was a close relative of the Dodo (Raphus cucullatus), the Rodrigues Solitaire, the extant Nicobar Pigeon.

Of the many species lost during the past 500 years, the Spotted Green Pigeon is one of the most mysterious.

The bird was first mentioned in the book ‘A General Synopsis of Birds’ (1783) by John Latham and scientifically named by Johann Friedrich Gmelin in 1789.

It was about 32 cm long and had a wingspan of 35 cm. The plumage was deep bottle green. The neck was characterized by elongated feathers. The wing and back feathers were spangled cream colored.

The only known example of the Spotted Green Pigeon is the Liverpool pigeon, which is currently in the World Museum, Liverpool.

Debate has periodically arisen around this specimen. Some scientists have speculated on the exact island it lived on – Tahiti being a popular choice, others have suggested it is not a unique species at all but a juvenile Nicobar Pigeon (Caloenas nicobarica), a bird still found today on the Andaman, Nicobar Islands and through the Malay Archipelago.

To solve the mystery of the Spotted Green Pigeon, Dr David Lambert of Griffith University and his colleagues took DNA from two feathers of the Liverpool specimen.

Because of its age, the DNA was highly fragmented, so they focused in on three DNA ‘mini barcodes’ – small sections of DNA which are unique for most bird species. They looked at these sections of the pigeon’s DNA, and compared it to other species.

This showed that the Spotted Green Pigeon is indeed a separate species, showing a unique DNA barcode compared to other pigeons.

“The bird is genetically most closely related to the Nicobar Pigeon and the Dodo and Rodrigues Solitaire, both extinct birds from islands near Madagascar,” said the scientists, who reported the results in the journal BMC Evolutionary Biology.

The Spotted Green Pigeon shows signs of a semi-terrestrial island lifestyle and the ability to fly.

“The closely related Nicobar Pigeon shows similar habits and has a preference for travelling between small islands.”

“This lifestyle together with the relationship of both pigeons to the Dodo and Rodrigues Solitaire supports an evolutionary theory that the ancestors of these birds were ‘island hoppers’, moving between islands around India and Southeast Asia.”

The birds that settled on particular islands then evolved into the individual species. The Dodo’s ancestor managed to hop as far as the island of Mauritius near Madagascar where it then lost the ability to fly.

“This study improves our ability to identify novel species from historic remains, and also those that are not novel after all. Ultimately this will help us to measure and understand the extinction of local populations and entire species,” said study first author Dr Tim Heupink of Griffith University.

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Tim H Heupink et al. The mysterious Spotted Green Pigeon and its relation to the Dodo and its kindred. BMC Evolutionary Biology 2014, 14: 136; doi: 10.1186/1471-2148-14-136