Friday, November 13, 2009

Side by Side

Once I got my Red-headed Woodpecker videos from this morning processed so I could frame through them, the striking similarity between them and Mike Collins' recent bird filmed at the Pearl were so obvious that the analysis took a lot less time than I expected. So here I'll just present two side-by-side comparisons of the Collins bird and a known Red-headed Woodpecker, which should abolish all lingering doubts as to the identity of the bird. I know it did for me.

Technical info: My video was shot this morning around 9 a.m. CST at the Meriwether Lewis grave site on the Natchez Trace Parkway in Lewis County, Tennessee, about 12 miles from my house. It is the most reliable year-round spot for the species in our area, consisting of many square kilometers of lovely oak-hickory forest. My video camera is regular definition, not an HD camera like Mike's. However, I was probably considerably closer to the birds, as I was in a National Park, near a campground, and they are quite tame. I shot with manual focus at a manually set shutter speed of 1/1000s and image stabilization on; I strongly recommend all people who attempt to use consumer video cameras to document rare birds to do likewise. Fast shutter speed and no autofocus are essential for hand-held video to prevent everything from turning into hopeless blur when zoomed; use the fastest shutter speed that lighting will allow. The results are less pleasant to actually watch, having a jerky quality; but the individual frames will contain vastly more usable information. My software will only give me 30 frames per second on deinterlaced video, not 60 frames per second as Mike has. So, when I line a frame sequence up side by side between the two, I have one frame for every two of Mike's. I also avoided zooming in too far or getting too close, as I wanted the images degraded somewhat to compare better with Mike's.

Now the results:

First, a comparison of frames where the wings are fully spread during banking flight. It is these frames especially that seemed to give intriguing long pointed wings and black only near the wingtip of the Pearl River bird. These are not entirely equivalent sequences. The lighting is different; my bird is substantially less backlit and in the middle frames the white underparts are well-lit. Also, in Mike's case the bird was in powered flight and I have grabbed the frames at comparable points in successive wingbeats; my bird was engaged in a banking glide without flapping and the frames are consecutive. Still, the illustrate very well both birds in a series of similar viewing angles (click for a larger view):

The structure of the two birds is virtually identical. The shape of the white secondary patch where it is well resolved in the latter frames is also identical between the two. There does appear to be slightly less black at the wingtip of the Collins bird; however the white in the secondaries appears to end at the same spot on both birds. I suspect that the backlight has blurred out the tips of the outer primaries on the Collins bird, making the black wingtip appear somewhat reduced. I certainly see no diference at all between these two birds that suggests in any way they are not the same species.

Next, a direct frame-by-frame comparison of one full wingstroke of both. As I was able to follow the Red-headeds around as they moved actively from tree to tree, I captured their flight from a variety of angles. I have chosen the one that is imaged the most clearly from an angle most directly comparable with the Collins bird. In the case of both videos, the chosen wingbeat occurs during bounding flight, where single flaps are separated by short folded-winged ballistic bounds (I call it "cannonballing"). This is typical of flickers, Pileateds, and Red-headeds, among other species of woodpeckers, when they are covering moderate to long distances. Also in the case of both the Collins birds and the Red-headeds I photographed, the structure, dynamics, and rhythm of the individual wingbeats in bounding flight are extremely consistent. So, the two wingbeats I have chosen (one from each bird) are quite representative of their respective flight styles. I have also included a sample frame for each bird showing it in mid-bound, with wings folded, viewed from the side, to compare the silhouette of body, head, and tail (click for a larger view):

The resemblance is striking. The structure and posture of both birds at the same stage of the wingbeat is virtually identical; the timing of the wingbeats is also indistinguishable. The structure and movement of these two birds are almost exactly the same. Their folded-wing silhouettes during the bound are also essentially indistinguishable.

The bird in Mike Collins' November 5th video is, beyond all reasonable doubt, a Red-headed Woodpecker.



At 7:10 PM, Blogger Mr. K said...

Like you said in an earlier post, Mike Collins has demonstrated incredible perseverance and more importantly, openness. I also really hope the Fishcrow succeeds, sooner rather than later. I would even hope his story is made into a movie! I would pay to see it.


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