Ivory-billed Woodpecker Wingspan and Body Length Measurements and Species Discussion, Drone Footage, LA
DRAFT
edit 9/20/22
edit 9/16/22
Due to the importance of putative Ivory-billed Woodpecker evidence, public ideas and raw work on the drone footage is being accumulated here. Sections have been written in early August 2022 as evidence, video iterations and ideas are released or appear. Reading this draft in reverse, (bottom up) will show the chronological evolution of ideas and conclusions more clearly.
If anyone wants to propose or present an organizational rewrite, please contact NBP or author.
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New, different measurement data, deduced from the 2/23/21 0800, drone footage by the C. Principalis Group, obtained in LA is presented. Independent data here, along with prior drone analysis by this author on possible species via plumage and vertical perching indicates this distant bird is an Ivory-billed Woodpecker.
This adds to the original researchers' "lines of evidence" for Ivory-billed Woodpeckers in this area. The body length of the woodpecker in the subject 2021 video was measured on ~ 8/10/22 and several steps were needed to be as accurate as possible on that date. That calculation indicated the length of the bird was 21.4 inches. This obviously closely matches Ivory-billed length and eliminates both Pileated Woodpeckers or Red-headed Woodpeckers if all other characteristics match known Ivory-billed details. Some other non-Picidae species that have lengths substantially different than 21.4 inches are also eliminated.
Here in late 8/22 is a calculation of 30.3 inches for the wingspan of the subject drone bird. The Ivory-bills' measured wingspan from various specimens is 29 to 31 inches with some sexual dimorphism, females being smaller.
The 30.3 inches for wingspan is empirical data from the actual video images; it needs to be written up neatly with
the exact methods, all intermittent calculations, subtotals and perhaps
some screen shots added. The wingspan measurement was pursued for obvious identification purposes. Careful social media posters were asking about a way to scale
the bird. Good insight by them and a rare, actual
question about the evidence.
Another poster experienced in drone photography asked on social media about how the
first set of numbers (body length) was derived, and that methodology is similar as for the wingspan here. That
person was asked a few short questions by me on any alternant methods; they remained unanswered until ~ 9/18/22. No other plausible method was offered to deduce measurements of the subject bird although climbing the tree with models for reenactment was proposed. That would be expensive, time consuming, slightly dangerous, involve liability and permissions that could be withheld.
Before doing this latest research, I had deduced a constant, -5%
adjustment (C = -5% for now) that is needed to compensate for the slight angle of
tree acquisition by the camera that causes foreshortening and influences
the actual tree height appearance on a screen to the actual height due
to perspective compared to the horizontal measurement of the wingspan
on a computer screen, which is not foreshortened. The constant's present
value (-5%), and actual estimated range, + - from -5% and weighting in determining the
final absolute number is very minimal and is a + - minus 0 to 1 inch
from the present final number (30.3 inches) when using C = -5%.
The exact elucidation of C will intuitively not change the wingspan more than a fraction of an inch or any of the assertions or conclusions in this article.
To deduce the unknowns of wingspan and body length only one object of known or satellite estimated length is needed. Via caliper on a PC screen, the video's woodpecker wingspan and tree height was measured to establish a ratio using the perch tree height (98
feet estimated) as the utilized height.
The ratio was used to calculate the previously unknown wingspan of the bird. The wingspan measurement was best deduced by using the final in-flight
frames of the regular speed sequence of the half flight iteration. There the bird flares out its wings, squared and approximately tangential to the camera lens.
Three measurements were made and averaged. Other frames were also measured but not summated; these frames will not
change the final results since they were the same as the three
measurements used.
Data, Measurements and Derivations for Wingspan
tree height in area equals 98 feet average per authors, and NBP GIS confirmation. Landing tree appears average
average n = 3, wingspan, 23/128 inch
tree height is 6 5/8 inches on screen
equals 768 plus 80 (128ths of an inch) = 848/128 inches
23/848 = .02712 .02712 x 98 ft = 2.658 ft
2.658 ft x in/ft = 31.89 in
31.89 minus (C adjustment of -5 %) - 1.59 in
equals 30.3 inch wingspan in subject bird
Project Principalis stated the average height of the trees in the study area is 98 feet. NBP checked GIS data bases and examined aerials; the 98 foot height is very close to the actual height of the landing tree.More ecological correlates support the landing tree height is approximately 98 feet. The maximum heights of the common tree species in the area are in general well over 100 feet. When the species are assumed to be the age of the trees in that area and extrapolated via minimum growth rates, 98 feet is approached.
Also you can see in the video that trees of seemingly the same species have varying DBH in the scene. The highest DBH trees and likely the oldest, have heights that are not much more that the smaller DBH trees. This indicates that these older individual trees have recently had more secondary growth (width) than primary growth (vertical). Dominant secondary growth occurs when trees are older and can be approaching 90 feet or more depending on species.
I am highly confident that the estimates of tree height and its derivatives, wingspan and length, are very close to the actual bird's morphology; it is surely not a Red-headed Woodpecker. Color fidelity in the video is adequate. Careful review, frame by frame of relative positions of the white and black during the flight cycle is sufficient to say this bird's dorsal wing pattern is very similar to an Ivory-billed and not a Pileated. The correct species choice depicted in this video leads to only one possible species.
This supports that the drone footage is of an Ivory-billed Woodpecker when combined with other data presented here including an analysis of body length, possible species, wing beat Hz, plumage, etc. below.
Body Length: The average height of the trees in the recently posted drone footage is 98 feet. Using the same methods as above to deduce the wingspan of the bird, the length of the bird is ~ 21.5 inches. This agrees with only one species of Picidae in SE USA.
Wingspan and Body Length: 30.3 inch and 21.5 inch respectively using the methods described within. The woodpecker in the drone is portraying measurements that do not agree with almost all SE USA Picidae species. The drone woodpecker's measurements agree closely with known and established Ivory-billed measurements of wingspan and body length measurements.
Plumage: Careful frame by frame plumage analysis throughout the flight cycle described within eliminates all NA species including known leucistic Pileated plumages. Unknown leucistic plumages of Pileated, which may or may not even exist, are eliminated by the length of the bird being ~ 21.5 inches. In addition, the flight dynamics do not agree with Pileated.
Parts of Article in Raw Form as of 8/27/22
Poster asks for info, doesn't do the math themselves, yes of course on FB.~ 8/26
"Can you do the same thing using wingspan, careful to include the black wing tips? If you do that I'd like to see if the results are similar. I think the wingspan on a ivory bill woodpecker is about 30"
Update on IBWO Evidence Review, Louisiana 2000-2022 Drone footage
The average height of the trees in the recently posted drone footage is 98 feet. That makes the woodpecker in the drone ~ 21.5 inches long which is right for only one North American species, the Ivory-billed. In addition the bird has largely white wings and black body which only fits IBWO. The bird zooms up for a landing that fits the literature for IBWO (Audubon, et al.). Upon landing the white saddle of an IB is seen. There is also the suggestion of a dorsal stripe.
This area has had sightings for over twenty years meeting the often voiced criteria of "repeated sightings are necessary". Recently game cam photos from the same area depicts birds that are Ivory-bills according to the research group's analysis. Independent review of the photos shows two birds mating in November, an unprecedented time for Pileated Woodpeckers.
Great job by the LA group.
Here is my post a week ago before I knew the height of the trees:
I have scaled the drone bird as follows: using the right landing tree range of possible heights to determine length of bird
if tree is, then bird length
60 feet 12.86 in
70 feet 15.00 in
80 feet 17.14
90 feet 19.28
95 feet 20.35
(note: because tail is unresolved I assumed the tail was average length meaning not an IBWO but RHWO, add ~ 1.0 inch to right column to adjust if bird is the length range of IBWO and well out of the range of RHWO.
From: I wrote this below earlier on 8/17 after the drone footage at regular speed was released. Had not figured out height of trees.
Link to right tree view, and bird is in next comment
It is a standard practice to provide different speeds including actual speed of various videos being used as "record videoes".
An issue for me of the drone half speed, and others a week ago was, what makes it a woodpecker? Many birds can sweep up for a landing on slanted branches.
But now looking more carefully with regular speed at the landing tree, that branch is close to vertical and the bird hitches up, woodpecker-like, and few other taxa other than Picidae do this.
Hz may be of imperfect or of nuanced ID assistance since this bird is mostly not in powered level flight but varied transient flight styles. This can include landing, taking off and possible searching for food or a landing substrate. The bird could also be hesitant if it is parallelling, mimicking or flanking the slight drone movement.
The initial take off includes a drop of ~ the first 50 horizontal feet to the right. Level powered flight is measured in IBWO (8.6 n =4) and PIWO (5.2 n ~ 100) with no overlap for this flight type between the species ever measured. The possibility that this bird is aware of and observing the drone (perceived predator) must be considered in relation to flight type and wing beat Hz.
Still working on this, but subject bird, for at least short sequences of several flaps or less seems high Hz (>6<7 for middle ~ 150 feet) for level flight of any PIWO (5.2). I also do not see the very noticeable wing binding that PIWOs show over ~ 150 feet. But the bird is not flapping completely constant as some binding is probable which may fit the 2006 or 2008 LA video more than any PIWO. The 2008 video seems to show some minimal or more binding.
Also I see the suggestion of wing bowing as Pulliam brought up for Luneau and is in the 2008 LA; this is inconsistent for PIWO which has a deeper wing flex on the downstroke with wing tips almost touching or touching. However comparing this to the powered level (close to level) flight of the Luneau video is not without nuances.
As far as confusing species which have some similar black and white pattern. Why is it not a lost Black-shouldered Kite? Black body might eliminate that but is that cherry picking frames as the black body is not seen in most frames? I do not see it as a kite as far as wing shape, chord width, landing and hitching up a vertical primary branch.
And there is Black-crowned Night-Heron but that should flap much slower than this bird. Also White Ibis and white phase or transforming imm. Little Blue Heron was in the running but trailing badly before these new drone sequences. Seems all 3 are eliminated as this bird Hz is too fast and not landing like or in a substrate like those do.
That may only leave Red-headed Woodpecker or IBWO. The bird seems large but why be subjective on such an important topic.
There is no scale provided with the video at this point although there are multiple ways to provide that. Scaling will provide a method to avoid or address the problem of the inconsistent amount of white in the mantle of this bird from frame to frame.
Since an IBWO is 100% longer than an RHWO that should eliminate one of these species. You provide scale and you may be squarely on Red-headed or Ivory-billed.
Fred Virrazzi 9/11/22 Social Media
