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The apparent rediscovery of the Ivory-billed Woodpecker Campephilus principalis in Arkansas, USA, …


Biology Articles » Zoology » Ornithology » Video analysis of the escape flight of Pileated Woodpecker Dryocopus pileatus: does the Ivory-billed Woodpecker Campephilus principalis persist in continental North America? » Methods

Methods
- Video analysis of the escape flight of Pileated Woodpecker Dryocopus pileatus: does the Ivory-billed Woodpecker Campephilus principalis persist in continental North America?

Video recording

Pileated Woodpeckers were attracted to a bird feeder containing suet at Grants Trail, Dayton, OH 45459. The suet feeder was placed approximately 2.1 m high on a tree trunk, and the distance to the suet feeder from the observation point was approximately 5 m. Birds on the feeder were startled by movement of window blinds on January 28 and February 5, 2006, and their escape flights were filmed using a Sony Hi-8 SteadyShot video camera at 29.97 frames s-1. At least two birds feature in the videos, male and female.

Analogue tape was converted to digital by connecting the Hi-8 camera directly to a Sony DCR-HC30 digital video camera and recording onto that camera's mini dv cassette. The resulting images were converted to an avi file using Windows Movie Maker on a Windows XP PC. The video is freely available in wmv format [14] and in avi format from the author or David Nolin (via the author). The video was decompiled using Blaze Media Pro (Mystik Media, Hampstead, NC, USA) for a detailed analysis. Import into Avid® Xpress Pro HD for deinterlacing did not reduce the wing flicker seen in the images, and further professional processing could not improve the resolution, so the original decompiled file was used for analysis. Hence some frames contain two overlaid images, which may lower the resolution in some cases. The decompiled file was examined frame by frame and compared to the decompiled images of the putative Ivory-billed Woodpecker presented in Fitzpatrick et al [1].

Wingbeat frequencies were calculated by noting the frame number of the midpoint of the downstroke of each wingbeat (e.g. Figure 1B, frame 758) and calculating the length of time taken per wingbeat as (number of frames between downstroke midpoints)/29.97.

Authors' contributions
JMC performed the data analysis and drafted the manuscript.

Acknowledgements
The author thanks David Nolin for making his video freely available for use by all interested parties, and for permission to reproduce frames. David Luneau is also thanked for permission to reproduce frames from his video. David Martin, while partly disagreeing with the conclusions, provided extensive comments that have significantly improved the paper. The referees are thanked for their extensive and helpful comments – both those who agree with the conclusions and those who do not – as it is clear that they spent much time on the paper.


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