Friday, 15 June 2007

Another nail in the coffin for Ivory-billed Woodpecker ‘rediscovery’?

First it was the barking calls of deer, and now it’s the ‘wing collisions’ of flying Gadwall. It seems that the so-called double rap calls of what search teams had believed must be the extinct Ivory-billed Woodpecker, somehow risen from the dead in the southern US, are now being claimed as anything but that impressive species.

The calls in question were recorded on remote devices placed by scientists from the Cornell Lab of Ornithology in cypress swamp habitat in both Arkansas and Florida, two states once inhabited by the world’s largest woodpecker. The recordings had, along with blurry video footage, formed a major part of the evidence supporting the claim of rediscovery when it was announced to the world at the US Department of the Interior back on 28 April 2005. But the ornithological establishment has been uneasy about the lack of hard evidence in support of the woodpeckers' continued existence, and this latest revelation suggests its fears could be well-founded.

The claim comes in a paper by Clark Jones and colleagues who, writing in The Wilson Journal of Ornithology (119(2): 259-262), say that the confusion with woodpecker raps may arise because of “close similarities in amplitude ratios, peak-to-peak times between raps, and auditory quality between ARU recordings and wing collisions from a Gadwall”.

Searchers in Arkansas and north-west Florida will receive little encouragement from this latest broadside, which seems set to explode the myth of ‘rediscovered’ Ivory-billed Woodpeckers. With further searches having failed to reveal new evidence, the original claim is looking increasingly tentative.

One thing has changed since the ‘rediscovery’ was made. The following year, analysis of Ivory-billed Woodpecker DNA from museum specimens led to the suggestion that birds from mainland North America and Cuba in fact represented separate species. Fleischer et al (2006) showed significant genetic differences between the two and evidence of a split more than one million years ago, meaning that the lost woodpecker of the south-east US bottomlands was in fact endemic to the region.

Although Cuba’s Ivory-bills have not been officially reported since the 1980s, persistent rumours that the species survives in remote and rarely visited areas in the east of the island perhaps now hold the best hope of an Ivory-bill rediscovery in the future.

* Read Cornell Lab of Ornithology’s discussion of similar sounds here.