Tuesday, July 26, 2005

Ivory-Billed Woodpecker: room for reasonable doubt

This spring, when news reports announced that the Ivory-Billed Woodpecker was alive, I was thrilled!!

Now, I'm not so thrilled.

Over the last week, I've read the paper, viewed the video, and carefully considered the evidence for myself. My conclusion: there is room for reasonable doubt here. I don't see convincing proof that eliminates an abnormally-plumaged Pileated woodpecker as a possibility.

The visual evidence includes a video and seven sight records.

The video: It's been described as "crummy" even by John Fitzpatrick, one of the authors of the Science paper. I agree with that assessment. It's basically a series of black and white blobs. On the flying bird, no details of the head are visible. On the stationary bird, look at Figure S5--it perfectly illustrates just how "crummy" the video actually is. The real-life stills show a black-white-black blob, and the comparable picture of a model Ivory-bill crisply shows the pale bill, white neck line ending before the bill, red crest, white dorsal lines converging on the back, and entirely white secondaries.

At this point, it may be natural to think: "Ok, maybe the video is inconclusive. But how about all those sight records?". For a typical sight record, you may be picturing a skilled observer patiently watching an Ivory-Bill hanging from a nearby tree. The observer is alternately peering through a telescope and carefully noting and sketching all known field marks. I admit that I was thinking along those lines when I first heard about all the sight records.

In reality, the typical real-world looks were fleeting looks at flying birds.

1. bird flying/landed, naked eye (?) at 20M (11 Feb '04)
2. bird flying, naked eye at 20M (27 Feb '04, two observers). no features of head or upper back noted by either observer.
3. bird flying, naked eye at 100M (5 April '04)
4. bird flying, binoculars at 100M (10 April '04)
5. bird flying, binoculars at 120M (11 April '04)
6. bird flushing, naked eye at 15M (9 June '04)
7. bird flying, binoculars at 80-120M (14 Feb '05)

A brief binocular look at a flying woodpecker at 100 meters is not ideal. A brief naked-eye look at 20 meters is also not ideal. Nowhere do I see a detailed description of the underwing pattern, or a description of a white neck line that ends before the bill, or a description of the pale bill itself, or a description of the two dorsal lines converging on the lower back. Apparent size can not reliably separate a large Pileated (average length =16.5 inches) from an Ivory-bill (average length = 20 inches). In short, I see nothing in any of the sight records that convincingly eliminates an abnormally-plumaged Pileated woodpecker.

There is also some audio evidence, but that is notoriously hard to distinguish from distant gun shots, blue jays, etc. I see audio evidence as useful in pinpointing possible areas for intense follow-up searches, or as supplementary to a given sight record, but never as standalone proof of Ivory-bills.

I'm not alone as a skeptic. In this New York Times article, David Sibley says "the evidence they've presented falls short of proof". The article also says that Kenn Kaufman did not think that the re-discoverers had proved their case.

The bottom line for me is that there is room for both hope and skepticism in the Ivory-Billed Woodpecker controversy. For proof, Sibley says that he wants "redundancy. Repeated sightings by independent observers of birds really well seen." I truly hope that such proof will emerge sometime soon.