The Ivory-billed Woodpecker Campephilus principalis is
or was one of the largest woodpeckers in the world, at roughly 20 inches
in length and 30 inches in wingspan. It was native to the virgin
forests of the southeastern United States. Due to habitat destruction, and to a lesser
extent hunting, its numbers have dwindled to the point where it is
uncertain whether any remain. The species is listed as critically endangered and possibly extinct.
The Ivory-billed Woodpecker has been seen and recorded.
The audio recordings were captured in two videos of birds with
characteristics consistent with the Ivory-billed Woodpecker. This
footage was obtained near the Pearl River in Louisiana, where there is a
history of unconfirmed reports of this species. During five years of
fieldwork, Dr. Michael Collins, had ten sightings and also heard the characteristic
"kent" calls of this species on two occasions.
Scientists working independently in three states have now published
articles that report multiple sightings of and various forms of evidence
for this elusive species, which is extremely difficult to observe and
photograph due to its rarity, wariness, and tendency to roam over wide
areas in remote swamp habitat. The two previous articles present
findings from Arkansas [Fitzpatrick et al., Science (2005)] and Florida
[Hill et al., Avian Conservation and Ecology (2006)].
During two encounters with an Ivory-billed Woodpecker, Collins heard
high-pitched calls that seem to match the description of an alarm call
that was reported by James Tanner in the 1930s but was never recorded.
On both occasions, the calls came from the direction of the bird and
began at a moment when the bird was alarmed. Several of these calls were
captured in the first video, which received a positive assessment from
an independent expert, Julie Zickefoose, whose paintings of Ivory-billed
Woodpeckers have appeared on the covers of a leading ornithology
journal and the leading contemporary text on this species. According to
Zickefoose, the large woodpecker in the video has a large crest, large
bill, long neck, and rared-back posture consistent with an Ivory-billed
Woodepecker, and it has ponderous and heavy flaps and takes an unusual
flapping leap that is unlike anything she has seen from a Pileated
Woodpecker (the only other large woodpecker in Louisiana).
The second video shows a bird in flight with flaps that are radically
different from the duck-like flaps that were expected, but a long
overlooked clue in a photo from 1939 suggests that there had been a
misconception about the flap style. The combination of the flap style
and the size rule out all species native to Louisiana other than the two
large woodpeckers, but several characteristics rule out Pileated
Woodpecker. This footage was obtained when an Ivory-billed Woodpecker
flew along the bayou below a tall tree that was used as an observation
platform, providing a view from an advantageous perspective of the white
stripes on the back and the white patches on the wings. A little over a
minute before the bird flew into view, the video captured a putative
double knock that matches a putative double knock that was recorded by
Hill et al. in Florida.
Collins began searching for Ivory-billed Woodpeckers in November
2005, shortly after Hurricane Katrina passed through the Pearl River.
His first sighting was on February 2, 2006, and then two weeks later he
discovered a "hot zone" a short distance up the same bayou, where he had
five sightings (two of exceptional quality) and also heard the
characteristic "kent" calls of this species on two occasions (once
coming simultaneously from two directions) during a five-day period. The
first video was obtained in the "hot zone" on February 20, 2006.
During the summer of 2007, Collins started climbing tall cypress
trees to watch for Ivory-billed Woodpeckers flying over the treetops in
the distance. The idea was to increase the encounter rate by opening up a
larger field of view. Professor Steve Sillett, of Humboldt State
University, and his colleagues, Jim Spickler and Michael Taylor, donated
their expertise and time as well as a full set of gear for climbing
trees. The approach provided results less than a year later, but not as
expected. On March 29, 2008, an Ivory-billed Woodpecker flew directly
beneath one of the observation trees, and Collins saw the definitive
white stripes on the back and white trailing edges of the dorsal
surfaces of the wings. Just over a minute before the bird flew into
view, the camera recorded a putative double knock that is consistent
with a putative double knock that was recorded in Florida.
Based on historical accounts of a duck-like flight, the Ivory-billed
Woodpecker was thought to have duck-like flaps in which the wings remain
extended throughout the flap cycle. Although definitive fieldmarks were
observed in the field, there seemed to be a contradiction when the
video was inspected and found to reveal a flap style that is radically
different from what was expected -- the wings are folded completely
closed in the middle of each upstroke. This mystery was resolved by a
long overlooked clue, a photo from 1939 of an Ivory-billed Woodpecker in
flight with the wings folded closed. The observed flap style makes
sense in hindsight since it is similar to that of other large
woodpeckers.
The flyunder video provides the first putative footage of an
Ivory-billed Woodpecker in cruising flight. Since the bird and its
reflection from the still surface of a bayou are visible, it is possible
to pin down the bird's position (which can't always be deduced from
video footage) by triangulation. Since the bird was initially flying
nearly directly toward the camera, it was possible to simultaneously
extract from the video curves that define both components (horizontal
and vertical) of the wingtip motion. Since the bird flew past reference
objects, it was possible to estimate wingspan and obtain the first
putative data on the flight speed of this species. The video also
provides the first putative data on the flap rate. The combination of
the wingspan and the flap style rule out all species native to Louisiana
except the two large woodpeckers, and in fact an expert on the flight
mechanics of woodpeckers, Professor Bret Tobalske, of the University of
Montana, is "confident it is a large woodpecker." The Pileated
Woodpecker is ruled out by the narrow wing shape, high flight speed,
high flap rate, and large white patches on the wings, all of which are
consistent with Ivory-billed Woodpecker. The video also shows a trace of
white on the back/neck that is consistent with the dorsal stripes that
were observed in the field.