Statistics, probability, and a failed conservation policy
Collins, Michael D. (2020), Statistics, probability, and a failed conservation policy, Dryad, Dataset, https://doi.org/10.5061/dryad.8w9ghx3hp
Many sightings of the Ivory-billed Woodpecker (Campephilus principalis) have been reported during the past several decades, but nobody has managed to obtain the clear photo that is regarded as the standard form of evidence for documenting birds. Despite reports of sightings by teams of ornithologists working independently in Arkansas and Florida, doubts cast on the persistence of this iconic species have impeded the establishment of a meaningful conservation program. An analysis of the expected waiting time for obtaining a photo provides insights into why the policy of insisting upon ideal evidence has failed for this species. Concepts in statistics and probability are used to analyze video footage that was obtained during encounters with birds that were identified in the field as Ivory-billed Woodpeckers. One of the videos shows a series of events that are consistent with that species and are believed to be inconsistent with every other species of the region. Another video shows a large bird in flight with the distinctive wing motion of a large woodpecker. Only two large woodpeckers occur in the region, and the flap rate is about ten standard deviations greater than the mean flap rate of the Pileated Woodpecker (Dryocopus pileatus).
Video footage was obtained during three encounters with birds that were identified in the field as Ivory-billed Woodpeckers. Several events that appear in the videos have been analyzed and published. The videos are provided here in raw digital form (interlaced). Deinterlaced versions and cropped versions that isolate some of the events are also provided. The first video was obtained in the Pearl River swamp in Louisiana on February 20, 2006, following the fifth sighting in the area that week. The 2006 video shows a perched woodpecker that appears to be larger than a Pileated Woodpecker and has characteristics and behaviors that are not consistent with that species. On March 29, 2008, another video was obtained from 23 meters up an observation tree that is located a short distance up the same bayou. The 2008 video shows a large woodpecker in flight (it passed nearly directly below the observation tree) that has fieldmarks consistent with the Ivory-billed Woodpecker and a flight speed and flap rate that are not consistent with the Pileated Woodpecker. The other video was obtained on January 19, 2007, in the Choctawhatchee River swamp in Florida while visiting a site where Geoff Hill and his colleagues had recently reported a series of sightings. Two birds were identified as Ivory-billed Woodpeckers on the basis of fieldmarks and spectacular swooping flights (some of which appear in the video) that are consistent with historical accounts of this species but are not consistent with any other species of the region. The 2006 and 2008 videos were obtained with a hand-held Sony DCR-HC36 standard video camera (captures at 720x480 pixels). The 2007 video was obtained with a Sony HDR-HC3 high-definition video camera (captures at 1440x1080 pixels) that was mounted on kayak paddles. The author is a scientist at the Naval Research Laboratory, but the collection and analysis of the videos was privately funded.
Raw digital video files (interlaced):
- event2007-1.mp4: downward swooping takeoff in 2007-1i.mov (plays at half speed)
- event2007-2.mp4: upward swooping landing in 2007-2i.mov (plays at full speed)
- event2007-3.mp4: horizontal takeoff in 2007-2i.mov (plays at half speed)
- event2007-4.mp4: takeoff with rapid wingbeats in 2007-2i.mov (plays at full speed)
- event2007-5mp4: upward swooping landing in 2007-3i.mov (plays at full speed)
- event2007-6.mp4: climbing and double knock in 2007-4i.mov (plays at full speed)
- event2007-7.mp4: downward swooping takeoff and upward swooping landing in 2007-5i.mov (plays at half speed)
- event2007-8.mp4: climbing after the landing in 2007-5i.mov (plays at half speed)