Tuesday, September 26, 2006

More Ivorybill Links

The paper reporting on the Auburn-Windsor team's search in the Florida panhandle has now been posted at the Canadian journal Avian Conservation and Ecology. The article includes a detailed explanation of why the team believes the recordings match ivory-billed woodpeckers and not other birds such as blue jays or red-breasted nuthatches.

Sounds that resemble Ivory-billed Woodpecker kent calls are produced by Red-breasted Nuthatches (Sitta canadensis), White-breasted Nuthatches (Sitta carolinensis), gray squirrels (Sciurus carolinensis), and Blue Jays (Cyanocitta cristata) (Jackson 2002, Tanner 1942), and may also be produced by Great Blue Herons (Ardea herodias) (R. Charif, pers. comm.). Neither species of nuthatch was detected at our site, either by experienced human observers or on our remote sound recordings. Great Blue Herons are common along the Choctawhatchee River, but their occasionally kent-like calls could be distinguished because they were followed in sequence by repeats of their more common squawk-like calls. Gray squirrels, which are plentiful throughout our study site and produce a “chuck” call with harmonic structure similar to the Ivory-billed Woodpecker’s kent call, could be distinguished on the basis of a drawn-out squeal that follows the “chuck.” Blue Jays have immense vocabularies of vocalizations (Tarvin and Woolfenden 1999) and may be able to produce notes that closely resemble Ivory-billed Woodpecker kent calls (Charif et al. 2005). Such vocalizations are atypical sounds for Blue Jays and should not be their exclusive vocalizations. If Blue Jays were the source of our putative kent calls, then kent calls should be commonly associated with more familiar Blue Jay vocalizations. However, none of the 210 putative kent calls recorded by our listening stations were associated with any known Blue Jay vocalizations. Between December and March, Blue Jays were absent from the core study area and were detected only at the edges of the swamp next to pine (Pinus spp.) stands. Blue Jays were not detected within the core study area either by experienced human observers or by our listening stations until the end of March, at which time both humans and listening stations recorded the appearance of Blue Jays, especially at the periphery of the study area. Numerous putative kent calls were heard by human observers and recorded by listening stations in February and early March, when no Blue Jays were present.
As I noted in yesterday's post, the recordings of calls and knocks are presented on Mennill's site.

In addition, Geoffrey Hill's website now includes his report on the ivory-billed woodpecker search in Florida. The site includes a pdf of field notes from the 14 sightings and photographs of bark scaling on freshly dead trees in the river basin. Most sightings were recorded by Brian Rolek, one of Hill's students, and Tyler Hicks, a research assistant, had the most detailed sighting. At least one sighting by Rolek was of two birds flying together. Hill emphasizes that the evidence is not conclusive but also insists that the sightings are of real ivory-billed woodpeckers and that he is confident in the work of his team. There are plans to return to the Choctawhatchee River this winter, and the team is taking applications to form a larger search team than last winter's.

The Toronto Star has a story with more quotes from the searchers. Geoffrey Hill explained the absence of good photographs or video by the difficulty of raising and focusing a camera on a bird in flight.
"Each of us could have shot an Ivory-billed by now because we had time to raise a shotgun. But video cameras are really hard to point compared to binoculars and shotguns," Hill said in an interview.
And beware the twitchers.
Especially worrisome would be an invasion of so-called "twitchers," sometimes fanatical birders armed with high-power spotting scopes who play back recordings to entice rare birds to appear.
Those high-powered spotting scopes sure are dangerous.