The Ivory-billed Woodpecker in Alabama, Past, Present and Future 

Draft 6/30/23, update Draft 2/26/25

The Ivory-billed Woodpecker's 21st century existence has been proven with thousands of pages of field data, sighting reports and supporting audio and video frames. Lingering however is the popular, erroneous dogma of its long-ago extinction supported by a refusal to accept its innate wariness and low detection rate. The Ivory-billed has been and is misunderstood by various bird record committees and understaffed, non-game department personnel. The commonsense bias, based on "none of us have seen the bird" rejects facts, several published papers, numerous field reports and the impacts of microevolution on this specie's modern behavior.

This context has led to many state bird record committees and state resource departments maintaining their dispositive, formal extirpation or extinction designation for the species. In light of what we have learned about Ivory-bills, these "conclusive" determinations were not based on science but on a commonsense bias and preserved today by face-saving apathy. 

How to judge the proportionality of culpability for the diminution of the bird's numbers is as difficult to agree upon as who is responsible for prolonging the falsehood that Ivory-bills were not seen after 1944 and into the 21st century.  

Here is an examination of Alabama, which would be similar for other SE US states, on how this bias and stagnant situation can be settled with field data. Utilizing proper, accepted field survey techniques would benefit the bird, birders, science and conservation. 

        

The Past  The Ivory-billed Woodpecker (Campephilus principalis) was a relatively common resident of forested areas in most or all of Alabama several centuries ago. It became restricted to wetland forests in south Alabama as the 19th century progressed. Some unconfirmed reports over the decades infer the Ivory-billed may have lingered in a few central and northern areas of the state into the 20th century.  Tanner writes, “By 1885 the birds had disappeared from North Carolina and northern South Carolina and from all the region west of the Mississippi Delta excepting the very southeastern part of Texas. By 1900 they were gone from almost all of Alabama and Mississippi.”

After the devastating Civil War, logging and poverty were extensive, and many local Ivory-billed populations were likely displaced and hunted to collapse.  

Description	Map of the range of the Ivory-billed woodpecker, pre 1860 (solid black line), 1891 (hashed area)
Date	April 1891
Source	The Auk, Volume 8, No. 2
Author	Edwin M. Hasbrouck

The last confirmed bird via specimen in Alabama was shot in the Conecuh River swamps north of Troy in 1907. There were subsequent Alabama sightings without an associated specimen. In the Florida panhandle, a small population was thought to persist post 2005 and perhaps into the 2020s in the Florida panhandle, near SE Alabama.
 

Conecuh River swamps just north of Troy, Alabama (red, upper middle of this map), was where the last AL Ivory-billed specimen was shot in 1907. This area is 200 miles due N of the Choctawhatchee River Water Man. Area in FL.

Today the forested riparian areas around Troy, Alabama are fragmented, with a narrow corridor of trees along wetland areas. Although these sinuous corridors have little chance of supporting breeding Ivory-bills now, they have in the past provided an acceptable, but now precarious greenway, connecting larger forest tracts of the SE USA.

But does Alabama have similar gaps in our understanding than almost everyone in the United States and Louisiana had in 1932? That year the colorful and well educated Mason Spencer insisted they were alive in the state and he could prove it. Although the last documented sighting of the species in Louisiana had been in 1899, he received a hunting permit and legally brought in an Ivory-billed he had just shot. 

Since several or more, Ivory-bills persisted into the 21st century, breeding must have occurred undetected for several decades in a heterogenous pattern. The remnant ribbons of habitat, connecting larger forest blocks, evidently allowed some periodic gene flow for the few remaining metapopulations or isolated family groups of Ivory-bills; this maintained at least some viability.  

The historical literature on the Ivory-billed in Alabama is limited. The classic Birds of Alabama by Arthur H. Howell, USDA, issued by the Department of Game and Fisheries of Alabama in 1928 is highlighted here. The work contains an introduction to the state's early history of field ornithology with a few pages on the Ivory-billed.   

Birds of Alabama, select pages

 

 

Ivory-billed Woodpecker, 1928 Howell:

 

Small part of the NBP analysis of the 2008 flyunder IBWO video (Collins, 2008 video, Virrazzi, 2022 paper and derivative videos)  

In 1942, the National Audubon Society issued its  Research Report No. 1, by James Tanner "The Ivory-billed Woodpecker". There are two pertinent mentions of Alabama IB locations; site fidelity should never be underestimated even if the areas were not continuously forested. Aerials should be viewed by experienced Ivory-billed researchers and subsequent visits arranged if warranted.

From Research Report No. 1, "The Ivory-billed Woodpecker":

   

In 1838, English naturalist Philip Henry Gosse lived and taught school for eight months in the community of Pleasant Hill, about 18 miles south of Selma in Dallas County. Two decades later, when he had become a prominent figure in British science circles, Gosse published "Letters from Alabama, Chiefly Relating to Natural History."

Gosse wrote of his encounters with the ivory-billed in the woods of Dallas County. Tanner notes the event in the Alabama Region of his report. The pair of birds he had come across, he wrote, were "rapping some tall dead pines, in a dense part of the forest, which rang with their loud notes."

In describing the bird's call and plumage, Gosse clearly knew the difference between the ivory-billed and the pileated woodpecker (The Huntsville Times, 2006; al.com, 2006).

USFWS - Recovery Plan for the Ivory-billed Woodpecker

In 2010, as a byproduct of the IBWO "rediscovery" in Arkansas 2004, the USFWS completed a Recovery Plan for the Ivory-billed Woodpecker

 
This is an important reference since it was compiled by many people from their accumulated knowledge, sources, data and files.

Here are the pertinent Alabama parts of the Plan:

In part due to the Big Thicket reports, the Southwest Region of the Service during the late 1980s initiated range-wide status review for the Ivory-billed Woodpecker and contracted Jackson (2004) to conduct the work. Jackson’s report provides a thorough review of all past reports and an assessment of whether the Ivory-billed Woodpecker could still persist in the Southeastern U.S. Jackson’s findings were inconclusive as he found no hard evidence to confirm the species’ existence but discussed in some detail his own possible encounters with the species. Jackson provides two accounts of his experiences, one along the Noxubee River in Alabama just across the Mississippi state line and the other in Mississippi along the Yazoo River confluence with the Mississippi River. For the Noxubee River account he glimpsed what he thought could have been an Ivory-billed Woodpecker in 1973, but no further evidence has emerged since the 1970s in Alabama. For the Yazoo River account, Jackson and his graduate student, Mr. Malcolm Hodges (who now works for The Nature Conservancy in Georgia), reported hearing a bird in 1987 that in their view closely matched the Cornell tape recording of the species. The bird in question apparently was responding to their playing of the Cornell tape, but never came in close enough for a visual contact, and Jackson and Hodges had no capability to record what they heard. In sum, there have been numerous reports of Ivory-billed Woodpeckers since the 1940s, and Jackson’s plea for the public to provide information during his status review resulted in hundreds of letters and phone calls to Service biologists. Most of these reports again were dismissed easily as misidentified Pileated Woodpeckers and in some cases Red-headed Woodpeckers. Still, as suggested above, tantalizing reports including photographs, tape recordings, and a feather suggest that Ivory-billed Woodpeckers could have persisted in very low numbers in highly isolated locations at least till the late 1980s. Nevertheless, near the end of the 20th Century there was absolutely no undisputed evidence acceptable to the scientific community to back up any claim that Ivory-billed Woodpeckers persisted past the 1940s. Thus, after more than a decade of relative silence, it came as a great surprise to many in the conservation community that an apparently solid report of a pair of birds had been observed in the late 1990s, this time along the Pearl River on the Louisiana side. Mr. David Kulivan, a wildlife student at Louisiana State University, waited a couple of weeks after his wild turkey hunting adventure during the spring of 1999 at the Pearl River WMA, but he finally contacted Van Remsen at the Museum of Natural History, Louisiana State University to discuss what he had observed. He claimed to have observed two Ivory-billed Woodpeckers, one adult male and one adult female, foraging together for about 10 minutes. Although he had a camera with him, he claimed he was too much focused on observing the birds to move an inch from his hunting position. After several hours of interviews, Remsen concluded that the details in Kulivan’s report were the most solid evidence he had heard in 22 years of keeping track of information to suggest Ivory-billed Woodpeckers are still extant (Williams 2001, Gallagher 2005).

  Appendix E.

Alabama (#’s where indicated are cross-referenced to Figure 6 in Tanner), subregions: (A) FL Panhandle, FL-AL, (B) Lower Tombigbee-Alabama-Mobile rivers, AL, (C) Upper Tombigbee River, AL-MS, (D) Pascagoula River and coastal Mississippi, MS, (E) Pearl River, MS-LA

1850-1859 (B-1) Near the Alabama River and Selma, Dallas County, AL; around 1850 (#6; two specimens now unaccounted for, but two specimens in Hahn dated “abt. 1850” may refer to these at the collection in Kessel, Germany) 

1860-1869 (B-2) Tombigbee River, Marengo County, AL (Tanner mistakenly listed MS); 1865 (#5; specimen now unaccounted for) 

1870-1879 None 

1880-1889 (A-6*) Blackwater River, FL (two specs.); March 1883 (Hahn; Tanner did mention this report but did not know location nor the
date) (B-3) Cypress Slough, 10 miles west of Greensboro, Hale County, AL; 1886 (#4; specimen now unaccounted for) (B-4) Wilcox County, AL;
1889 (#7) (C-1) Monroe County, MS; 1885 (#1) (C-2) Crump Springs, Lamar County, Buttahatchie River, AL; 1886 (#2) (C-3) Clay County, MS; 1885
(#3) (E-1) Near Bay St. Louis, MS; 1885 (#9) 1890-1899 (D-1*) Mississippi City, Harrision County, MS (two specs.); March 1893 (#10; Hahn 1963 also lists a specimen taken in April 1893 included in total
here) 

1900-1909 (A-1) Conecuh Swamps, north of Troy, Pike County AL; 1907 (#8; specimen now unaccounted for) (D-2) Big Black River, MS (one pair reported by M. Vaiden); 1908 (Jackson 2004, USFWS 2007)

 1910-1919 None 

1920-1929( D-3) Pascagoula Swamp, Jackson County; December 1921 (#11) 

1930-1939 (A-2) Escambia River, FL; 1936 (Weston 1965, Stevenson and Anderson 1994) 1940-1949 (A-3) Perdido River, FL; 1945 (Weston 1965, Stevenson and Anderson 1994)

 1950-1959 (D-4) About 30 miles north of Meridian, MS (B. Chauncey); 1953 (Moore 1954, Jackson 2004) (E-2) East side of Pearl River, adjacent to lock #1, St. Tammany Parish, LA, Hancock County, MS (one male foraging on sweet gum, by J. Merritt); October 1955 (USFWS 2007) 

1960-1969 (A-4) Eglin Air Force Base near Yellow River, FL (two birds seen Boiling Creek; B. Brown and J. Sanders reported to Dennis); August 1966 (Jackson 2004) (D-5) Leaf River swamp (1 mile north of US Hwy 98), Perry County, MS (2 seen briefly in “big gum” trees); December 1960 (USFWS 2007)

 1970-1979 (C-4) Noxubee River, near junction with Tombigbee River, Sumter County , AL (possible f lyby by J. Jackson); March 1973 (Jackson 2004) (D-6) Near where Black Creek joins Pascagoula River, Jackson County, MS (one possible heard “kenting”
but never seen by R. Sauey and C. Luthin); January 1978 (Jackson 2004)

1980-1989 (D-3) West side of Pascagoula River, north of Vancleave, Jackson County, MS (two birds in a pine by M. Morris); February 1982 (Jackson 2004) (E-2) Pearl River, St. Tammany Parish, LA (a male observed one year, a female the following year, both by N.
Higginbotham); 1986, 1987 (Steinberg 2008) 

1990-1999 (E-2) Pearl River, St. Tammany Parish, LA (a pair reported seen for 10 minutes by D. Kulivan while turkey hunting; extensive followup searches in subsequent years unsuccessful); April 1999 (Jackson 2004) 

2000 -2009 (A-5) Choctawhatchee River, FL (multiple visual and auditory encounters by many observers, including many recordings of putative kents and double-knocks and a very poor video); 2005-2007 (Hill et al. 2006, Hill 2007) (E-2) Pearl River WMA – Stennis Space Center, St. Tammany Parish, LA, Hancock County, MS (multiple sightings, several very poor but at least one suggestive video in 2006 of a large woodpecker, possibly lacking red in the crest; a more recent video of a woodpecker in flight in 2009 was determined to be a Red-headed woodpecker, a 2008 video is still undergoing review by M.
Collins and others); 2000, 2005-2009 (USFWS 2007; Collins 2005-2009

Fill in Alabama info here here here her 

The Present  There has not been any modern evidence presented for the Ivory-billed Woodpecker's recent existence in Alabama to my knowledge.  The species has been called extirpated for decades without any formal field work completed. 

Bob Harrison of Alabama, a long-time searcher for Ivory-bills, claims ~ 9 Ivory-billed encounters but some or all of these encounters may have been in Arkansas or other states. In 2006 Harrison, a wildlife photographer and then an Oakwood College professor credited as one of the co-discoverers of the ivory-billed in Arkansas, thought there was still a chance the bird could be in Alabama (The Huntsville Times, 2006; al.com, 2006).

In the January-February issue of Birdwatcher's Digest, 2006, Harrison said he thought Ivory-billeds might be hanging on in other Southern swamps. In Alabama, he mentioned the
Tensaw Delta north of Mobile Bay and the Pea River as possible areas to search.

Over the decades, the compilers of official state bird checklists have understandably moved the Ivory-billed into the extirpated or extinct category. The keepers invariably rely on the lack of reports, or credible reports, or dismiss credible reports as mistakes over the decades, to feel comfortable with this designation. Is this conclusion based on science, such as any formal point surveys, or organized surveys, for example? No.

It relies on common sense which is a bias that occasionally leads to mistaken and premature conclusions; there are innumerable examples of errors in varied disciplines when relying only on strong feelings.  

The Ivory-billed has an extremely low detection rate when using most informal birding techniques. It's wary and observant per historical and modern reports. Searches for Ivory-bills require careful planning, staffing and execution. 

Top areas to search for Ivory-bills in Alabama according to NBP's field data and ranking model: see NBP files

In 2023 Alabama state biologists were contacted to see how they determined the Ivory-billed was extirpated per the Alabama state checklist. It was confirmed there had been no formal or scientifically based survey performed in Alabama for Ivory-bills. Therefore, it is not known if there are any Ivory-bills in the state although we do think the species is close to extinction in Alabama and the USA.

There is some interpretive confusion between the last sighting and last specimen amongst state biologists. The personnel were courteous and professional. In an email below it's evident that IBWO sightings without the taking of the bird for a specimen evidently delegates the few, post 1907 sightings to not worth mentioning in the opinion of some of these scientists:

"The last known observation of Ivory-billed in Alabama was in 1907." 

This may be a manifestation that most natural resource departments share; they concentrate on fish and game species and without a specimen it's all just another tale about the monster bass that got away.

However, the state was far from completely logged over by 1907; it was possible for a few forest interior birds to eke out an existence without being seen by a "crowd" or shot. Skeptical dogma set in motion the Mason Spencer shooting of an Ivory-billed in 1932. The Singer Tract was only 170 miles from Alabama; unproven skepticism that the bird existed doesn't end at state lines or after 1940.

Underestimating the difficulty of finding this bird, with a large pair range, even when there, continues to this day.

By 1850 a large, east to west swath of central Alabama was already partially logged over. By 1926 about 40 forested areas of 25,000 acres each existed according to the USDA (see below). In the 1930s Tanner briefly visited a few pertinent IB forests of Alabama and found them cutover. Tanner missed counting 12 birds in Mississippi, alive in the late 1930s.

The 40 forested Alabama areas, totaling, 1,000,000 acres of virgin forest that stood until at least 1926, likely held IBs in Alabama past the "last confirmed" sighting of 1907.

Did these forty, 25,000 acres areas of virgin forest in Alabama have any Ivory-bills after decades of post Civil War poverty and associated subsistence hunting? The many rifle wielding outdoorsmen moved interstitially between the cotton and tobacco fields and into the shaded forests; some of them went hungry if bloodied fur or feathers didn't reach the pot.

          

1926 Virgin Forest 1,000,000 acres Alabama

Email response from Alabama to questions:                          

From: Alabama DCNR
Sent: Friday, September 1, 2023 11:15 AM
To: National Biodiversity Parks <; GOV>
Subject: RE: Ivory-billed Woodpecker ALABAMA

Historically, Alabama has conducted symposiums to bring together experts covering each taxa group, birds included, periodically to address rare and endangered animals in Alabama and to assess their status, provide management and conservation measures for those species, and to review species lists for the state.

The first of this type symposium was conducted in 1972, with a follow up a few short years later with a second publication coming out in 1976. At both of these meetings, Ivory-billed Woodpecker was discussed. The last known observation of Ivory-billed in Alabama was in 1907. Expert and well-known ornithologists of Alabama came together and agreed on the language that you see in the attached species accounts, that it was ‘highly doubtful if any Ivory-billed Woodpeckers occur in Alabama’ and ‘The Ivory-billed Woodpecker may now be extinct’.

In the 40+ years since these publications, many trained ornithologists have spent time throughout the state and significant time down in the Mobile-Tensaw Delta region, where one would suspect an Ivory-billed Woodpecker to be if there are any in the state, and have not heard or seen any signs of the species, or any indication that would lead us to change the status of the bird in Alabama.

We have not gotten any credible reports of IBWO in Alabama in the time that I have been with the state, since 2010, that would cause us to adjust the current status of the bird in Alabama.

 Nongame Wildlife Program Coordinator

 

Alabama Wildlife and Freshwater Fisheries

64 N. Union Street, Suite 584

Montgomery, AL 36130
- - - - - 

Results of years of advanced point survey dta for Ivory-bills by NBP. Exact locations removed. 

Survey Method Comments

Any brief, formal surveying in Alabama done by Cornell University (CLO, Mobile Team) per the Ivory-billed Recovery Plan was poorly designed.

All the Ivory-billed Mobile Team data utilizing anthropogenic double knocks (ADKs) in the SE USA circa 2006 –09 is suspect; it likely produced false negatives by alerting or driving away IBs before they were detected. It should not be used as evidence by the USFWS, any entity, or anyone to declare Ivory-billed absence vs presence in any surveyed areas of Alabama or elsewhere.

Cornell University (CLO, Mobile Team) utilized survey methods that erroneously extrapolated the vigorous response rate of a territorial and non-hunted congeneric, the Pale-billed Woodpecker, to an assumed response rate of Ivory-bills. C. principalis is not territorial and was incessantly hunted sometimes by imitating and/or following the most consistently knocking individual and shooting any bird encountered for a hundred years. 

As a formally designated federal breeding bird surveyor utilizing well established USFWS methodologies National Biodiversity Parks, Inc. (NBP) used a different ADK method, getting results that were 300 % or more effective in eliciting Ivory-billed' responses than CLO's Mobile Team.  M. Lammertink (CLO) was contacted when it was discovered that CLO had been doing 14 ADKs in 6 minutes compared to NBP’s designed and approved, 2-4 ADKs in 6 minutes. 

NBP has the largest unpublished IBWO field data set for ADK responses (~ 670 data points acoustically covering over 130 square miles of good to excellent IB habitat) from 3 states and a separate control state that had no Ivory-bills. We have had Ivory-bills respond within 40 miles of SE Alabama. 

NBP's zoologists have been to Belize, Costa Rica, Panama, Colombia, Ecuador, etc. over 30 times. Pale-billeds, etc. are embarrassingly easy to "get knocking". 

Hypothetically if we collectively hunted and shot every Pale-billed for one hundred years the remaining birds would not be liberally knocking. The literature has historical accounts of subsistence hunters or Ivory-billed collectors hearing DKs or even producing ADKs in order to locate, kill or try and kill IBs. Microevolutionary mechanisms impacted modern behavior of IBs in regard to the frequency of their knocking and kenting; the withering and unfortunate selection pressure of hunters/collectors eliminated birds that signaled excessively. 

As it was inherently obvious 20 years ago to some, it certainly has been confirmed that Ivory-bills are wary animals; forcing 7 ADKs into a minute and then another 7, five minutes after, likely repels or warns IBs that a predator is near, or at best, that the survey knocks are not being produced by a real or normal Ivory-billed. 

The disruptive, super stimuli, ADK method (CLO/USFWS 2004 method) should not be utilized for modified Ivory-billed point surveys.  

Position of The Department of Conservation and Natural Resources of Alabama on the Ivory-billed Woodpecker

The Department of Conservation and Natural Resources of Alabama follows the Alabama Ornithological Society's (AOS) official state bird list.

The AOS list is as follows:  

 Extinct/Extirpated Species

Pigeon, Passenger Woodpecker, Ivory-billed N Parakeet, Carolina Warbler, Bachman's N

 Total Species: 455

The Department of Conservation and Natural Resources of Alabama IBWO information

SCIENTIFIC NAME:

Campephilus principalis

 

STATUS:

Extirpated. Historical breeder. Listed as endangered by the U.S. Fish and Wildlife Service.

 

HABITAT:

Was found in virgin cypress and bottomland hardwood forests.

 https://www.outdooralabama.com/woodpeckers/ivory-billed-woodpecker

 

Geoff Hill PhD, is an ornithologist with Auburn University, Alabama. Hill was a co-author of a peer- reviewed paper on the evidence of the Ivory-billed Woodpecker in the Panhandle of Florida (2007) only an hour's drive from Alabama. Hill is aware of Alabama's pertinent IBWO habitat as an established field birder in the state. His well-educated opinion is that the Ivory-billed may be in Alabama.

Here are some of his comments from a recent interview:  

Choctawhatchee River, Florida  

"How possible is it that the ivory-billed woodpecker could make a reappearance?"

 

"Since ivory-billed woodpeckers are still flying around forests, at least in Florida and Louisiana and probably in Alabama and Mississippi as well, I would say that it is just a matter of time."

Hill said there’s been no recent evidence of the ivory-bill in Alabama, but areas in the Mobile-Tensaw Delta could be an ideal habitat if the bird were to make a recovery. He also said:

 

“If they are recovering, there’s plenty of habitat for them now,” he said. “The Apalachicola River system, the Choctawhatchee, the Conecuh River system, and the Mobile-Tensaw Delta are just huge wetland habitats for those birds. So, if they are able to reproduce, and their populations aren’t so small that they’ve lost all their genetic diversity, they have plenty of room to come back into.”

Ivory-billed Comments by G. Hill

 

Hill has always been a bit "forgiving" or "optimistic" on the exact type of forest habitat that the Ivory-billed needs to increase its numbers. Regardless, NBP believes there is a small chance that Ivory-bills can be occasionally breeding in very low numbers in Alabama. Ivory-bills have almost certainly been using the state to search for food, mates or appropriate breeding habitat post Singer Tract.  

The Future -- Ivory-billed Woodpeckers may or may not be extirpated in Alabama. Regardless of the reasons for past assumptions of extirpation the species is important to Alabama since one of the state's prestigious scientists from its premier university proposes that Ivory-bills may be still gracing the state.

 Hill of Auburn University Ivory-billed Book

The Ivory-billed has obvious value to outdoor recreationists of many types. Just knowing Ivory-bills are in a state or riparian corridor stimulates ecotourism and brings economic benefit to outdoor centric businesses that need customers and visitors. Birding is a growing outdoor activity stimulating hundreds of millions of dollars in economic activity. 

The Ivory-billed has economic value to rural communities; the species is not an impediment to the timber industry, or hunters, if stakeholders agree that cooperative management for this species can be agreed to.  NBP has developed low impact, inexpensive methods to address this specie's needs.

As an ecological basis for economic value Ivory-bills may be more valuable than has been discussed. Increasing their numbers could have modern forestry benefits. SE USA forest productivity could be 5 to 10% higher when a state's biodiversity includes a healthy population of Ivory-bills. However it's realized by most that the recovery of the Ivory-bill has a small chance of success; regardless certain actions should take place. 

Ivory-billeds had to "break into" the seemingly crowded Picidae avifauna of the SE USA. Evolving from the parent Imperial Woodpecker, which had the prerequisite bill and body size to access the phloem and cambium feeding invertebrates earlier than any potentially sympatric Picidae species; the IB fit an open niche.

A Imperial Woodpecker B Ivory-billed Woodpecker C Pileated Woodpecker 

The phloem and cambium, under the bark, of a stressed, damaged or dying tree are relatively rich in carbohydrates and proteins. The Ivory-bills  access these xylophagous invertebrates under the bark sooner than many other species of woodpeckers, other animals, or smaller species can. 

The competitive exclusion principle, if applicable, predicts that an open niche needs to be present and then exploited to grow species richness in a biotic community. The Imperial Woodpecker had the prerequisite morphology that led to the successful speciation into the northern Campephilus clade. One million years ago, soft and hardwood trees from Proto-Texas to Proto-Alabama and elsewhere were being debarked ~ one to three years earlier than any sympatric Dryocopus could accomplish the feat.

Once some bark is removed from a trunk more cambium is exposed, and the more cellulose dominant part of the heartwood is eventually completely available to the community of fungi, bacteria, insects, woodpeckers and mammals to continue the decay process.

Ivory-bills accelerated the tree to soil cycle by several years, increasing forest productivity. More efficient SE US forests can potentially be worth billions of dollars more per annum. The past or potential economic benefits of a healthy Ivory-billed population have likely been overlooked by our natural resource managers; they are not trivial. Unfortunately it's likely too late to restore the specie's advantageous impact to forest productivity for multiple reasons. The Ivory-billed still has substantial presence value. 

NBP's scientists have been carefully examining the literature and habitat aerials of Alabama. Our point survey methods have detected Ivory-bills in a matter of weeks.

We recommend that an actual scientific method be researched, proposed and enacted to explore a few, specific areas of the state for Ivory-billeds. Only advanced, field-tested methods designed for this species can yield valid information that serves the citizens and outdoor enthusiasts that enjoy the natural resources of Alabama.  

Raw Data and resources below

Sunday, March 12, 2006
Huntsville Times

As winter recedes, crews of birdwatchers, both amateur and
professional, are still scouring the Big Woods swamps of
eastern Arkansas for the ivory-billed woodpecker.

Closer to home, some natural questions arise: Did the
ivory-billed woodpecker ever live in Alabama? If so, where
- and when? And could a bird that still exists just one state
away also still exist in Alabama?

The ivory-billed did, indeed, occur in Alabama, mainly in
the southern pine and hardwood swamps of the coastal
plain. But one portion of its range extended into northwest
Alabama, along the Buttahatchee River, a tributary of the
Tombigbee.

When? The last confirmed sighting of the ivory-billed in
Alabama occurred "about 1907," according to Arthur H.
Howell in his 1924 book "Birds of Alabama."

The time and place - in the Conecuh swamps north of Troy -
were related to Howell by C.W. Howe, a trapper.

Howe was certain about his encounter for one simple
reason: When he saw the bird, he shot and killed it.

By the time of his book, Howell wrote, the ivory-billed had
"undoubtedly" disappeared from Alabama. Indeed, since
Howe's kill of 1907, there have been no accepted sightings.

So you have to go back before Howell to records from the
19th century:

In 1838, English naturalist Philip Henry Gosse lived and
taught school for eight months in the community of Pleasant
Hill, about 18 miles south of Selma in Dallas County. Two
decades later, when he had become a prominent figure in
British science circles, Gosse published "Letters from
Alabama, Chiefly Relating to Natural History."

Gosse wrote of his encounters with the ivory-billed in the
woods of Dallas County. The pair of birds he had come
across, he wrote, were "rapping some tall dead pines, in a
dense part of the forest, which rang with their loud notes."

In describing the bird's call and plumage, Gosse clearly
knew the difference between the ivory-billed and the
pileated woodpecker.

In 1891, in an article in The Auk, the journal of the
American Ornithologists' Union, Edwin M. Hasbrouck
surveyed the status of the ivory-billed throughout its
historical range. And that range, Hasbrouck concluded, was
rapidly shrinking as habitat disappeared.

Hasbrouck's essay contains one short paragraph about
Alabama. He told of individual birds being "taken" in 1865
in Marengo County and on the Black Warrior River near
Greensboro the following year. Hasbrouck also noted the
reported 1886 sighting on the Buttahatchee River at Crump
Springs and a nesting bird in 1889 in Wilcox County.

That's about it. In 1942, in James T. Tanner's exhaustive but
readable "The Ivory-Billed Woodpecker," Tanner checked
out the locations mentioned by his predecessors, but in
Alabama he found nothing.

By 1960, when Thomas Imhof's "Alabama Birds" was
published, there was little to do except restate the earlier
records and reports.

What about today?

Bobby Harrison, the wildlife photographer and Oakwood
College professor credited as one of the co-discoverers of
the ivory-billed in Arkansas, thinks there's still a chance the
bird could be found in Alabama.

In the January-February issue of Birdwatcher's Digest,
Harrison said he thinks ivory-billeds may be hanging on in
other Southern swamps. As for Alabama, he mentions the
Tensaw Delta north of Mobile Bay and the Pea River as
possible candidates.

The ivory-billed woodpecker in Alabama? I think it's a long
shot, but in 30 years of birdwatching I've learned there's a
very big difference between the unlikely and the truly
impossible. We hope for the former - and prepare for the
latter.

John Ehinger's Birdwatching column appears monthly on
the Outdoors page.


© 2006 The Huntsville Times
© 2006 al.com All Rights Reserved.

The Population of Ivory-billed Woodpeckers before Anthropogenic Effects with a Comparison to Imperial Woodpeckers

draft 7/10/23 then 7/15 7/17

Abstract. The formal literature on the Ivory-billed Woodpecker, Campephilus principalis, was reviewed and analyzed to establish an estimate of total population before anthropogenic effects for the species.

Exploring past population dynamics of Ivory-bills provides more information on natural trophic processes and niches that can be economically important to forestry and silviculture. The potential value of the species has been ignored which lessened, and lessens the management response by federal,  state and local governmental departments.  

Ivory-billed Woodpeckers were estimated to have a population of 57,696 animals 18,000 years ago (YA). Taking the above number of pairs, 28,848, potentially producing 2.11 fledglings per year per pair (Tanner 1942) gives 60,869 fledglings estimated in an assumed average year.

Total hypothetical maximum population after an average breeding season is estimated by combining adults and fledglings; 57,696 adults plus 60,869 fledglings, equals 118,565 Ivory-bills post breeding, 18,000 YA.  The population of all species of birds drops post breeding due to predation disease, age, food resources etc.    

Introduction

The formal Ivory-billed Woodpecker, Campephilus principalis literature concentrates on the specie's range, description, specimen records, interactions with other species including people, life history based mainly on the Singer Tract, LA and modern presentations of sightings and evidence. In an extensive literature review few details on the total population of the species from any date or time scale other than the 1930's (Tanner, 1942) was located. Minimal information can be found about the numbers of these large woodpeckers before anthropogenic effects began in the southeast United States.

The only detailed study of Ivory-billed Woodpeckers. (Tanner 1942) 

The Ivory-billed Woodpecker, if at carrying capacity, is a keystone species of significant ecological importance. Primary cavity nesters, such as woodpeckers, support community biodiversity and especially secondary cavity nesters. Picidae are an integral component of forest ecology. 

The species past or possible economic importance is potentially substantial, but ignored; sustainable forestry was mostly unknown in prior centuries or deemed unimportant since forests were erroneously assumed to be impeding agriculture or a source of infinite firewood, fence posts, board feet, game animals, etc.

Ivory-bills with their unique and powerful bill and body morphology begin the pivotal "Tree to Soil" cycle ~ 24 months or more before any other Picidae can remove bark from a senescent tree exposing the cambium and heart wood. An intact Ivory-billed population can hypothetically increase long term productivity by up to 5% in some southeastern US forests as primary productivity, natural decomposition and silviculture regeneration rates are accelerated. 

NBP's artist D. Tattoli draws Ivory-bills unique bill. Green lines indicate that the IBWO has its eyes positionally lower on head than the Pileated Woodpecker

Ivory-billed Woodpeckers are relatively efficient within the Picidae at physically removing the hard bark covering of stressed or dead trees speeding up forest cycles, while converting wood boring insects into avian biomass. The ancestor species of the three northern clade species likley had  

C. principalis has been noted to eat small beetle larvae (Dendroctonus spp.) prevalent under bark of recently stressed or dead pine trees. These beetles are considered one of the most important causes of economic loss in forestry (Ungerer 1999). Ivory-bills are a natural control on forest boring insects but the USDA, US Forest Service and the USFWS are confronted with fragmented, managed forest blocks and policies that immediately default to costly pesticides, or tree removal to address insect outbreaks. A balanced approach that included Ivory-billed management over the last 60 years may have resulted in a better integrated, efficient and effective result if coordinated governmental forestry and wildlife goals are properly merged. Department wide and interdepartmental MOAs united in a sustainable goal could have greatly lessened the large costs of pesticides and increased forest output while retaining biodiversity. 

The most efficient ecosystems for converting solar energy into plant material and vertebrate biomass are the complex assemblage of biodiversity in East Africa.

"The combination of volcanic soils combined with the ecological impact of the migration results in one of the most productive ecosystems on earth, sustaining the largest number of ungulates and the highest concentration of large predators in the world." Source: UNESCO--Productivity of the Serengeti

The Serengeti produces a much greater biomass of plants and animals than anthropogenically managed open spaces. The assemblage of animals there accelerates basal rates of primary production and regenerative cycles. The Ivory-billed efficiently contributed to forest regeneration for possibly a million years. The Ivory-billed is a relatively large, understudied, forest bird; a keystone species that likely can increase economic output of some US forests if properly managed.    

The US Department of the Interior, the US Fish and Wildlife Service, etc., have not properly valued the potential irreversible economic impact if the species is perpetually lost. Government entities have historically and recently underfunded the research, management for, and protection of, this valuable natural resource despite being mandated to preserve economic, recreational and natural resources for present and future American generations. 

Exploring past population dynamics of Ivory-bills provides more information on natural forest processes that can be economically important to forestry and silviculture; Ivory-bills are an important resource but of course being critically endangered their beneficial impact is now miniscule.  

Using the data and constructs detailed here an estimate is calculated for the total Ivory-billed population circa 18,000 years ago (18K YA) before many people (Pre-Clovis or Clovis) had arrived in the SE USA. By the 19th century there were certainly less birds than 18 K YA as anthropogenic effects were substantial; habitat destruction combined with increasing and more efficient direct taking of birds had and was accelerating.   

Tanner (1942, p.31) said this about recent historical times:

None of the earlier accounts of the Ivory-billed Woodpecker contained accurate or definite statements as to the abundance of the bird. Judging from the interest that naturalists and collectors had in the Ivory-bill, and the accounts they wrote, it was never common. Most writers mentioned the Ivory-bill as being a rare bird, or an uncommon one, and some heightened the difficulties they had in securing specimens. 

And:

Audubon usually described the big woodpecker as being quite rare.

As an example in North America, there have been estimates of the American Bison population number that are derived from descriptions and direct field observations related to the size of large herds. From such recollections and accounts, historians, anthropologists, and zoologists have estimated the original or pre-settlement population size for the species. 

For the Ivory-billed, a forest interior species, we will never have an answer on historical numbers meeting today's standards of modern wildlife research, which demands random or systematic sampling and replication. But the estimates that have been made for the American Bison and other species show us how numbers are deduced.

Any estimate of a derivative of a dynamic complex ecosystem will have uncertainties. For example, it is not realistic to presume that before the Pre-Clovis and Clovis cultures reached the southeast United States that the Ivory-billed population was stable. Floods, droughts, large ice or log jams, beavers, insect outbreaks and fire regimes caused landscape scale ecological impacts pertinent to the Ivory-billed population demographics.

Riparian forest aerial, a small portion of the Ivory-bills possible habitat today; the remaining acres are greatly reduced and of lower quality and heterogeneity.  

 

Methods

Three approaches have traditionally been used to estimate animal population sizes: direct observations, estimates of numbers killed, and estimates based on carrying capacity. There is enough Ivory-billed observations to deduce a total population estimate since in its simplest form it equals the species entire range (breeding range) times the number of birds per area as reported from the field. 

Some animals are relatively simple to count

For the Ivory-billed, historical observations inclusive of birds killed are used as base line data yielding animals per area. Tanner and others have examined these basic densities. Ecological interpretations on what was the likely total range of the species such as typical impacts of latitude, ocean currents, plains effect, etc., on climate and carrying capacity are utilized here. 

On age demographics, including the ratio of non-breeding adults to breeding in the few historical metapopulations studied, there is little data. Conclusions on age structure, with veracity, could be made by examining A. T. Wayne's extensive field notes and papers which were not available online (personal communications, 10/2022). They can be accessed by a visit to the Charleston Museum of Natural History. Combining Wayne's info et al. with a coordinated examination of most or all skins, noting plumage details, age, molt, etc. would provide some information on the numbers of animals in respective age cohorts of the species. 

Here this work rationalizes, or perhaps idealizes, the following unknowns: The pertinent field studies' birds, at Wacissa and California Swamps, which were counted as breeding adults, may not have all been adults. This research, roughly negates or nets out two drivers as following:  the number of adult birds that were missed in the verbal population estimates of the time equals the number of birds that were actually fledglings, but counted as adults.

Undercounting actual numbers via field encounters and number of birds shot is very likely even in formal field studies since detection rates are needed (Buckland, et al., 2010).  A. T. Wayne was collecting rather than studying the birds; this makes Tanner's research work important in the context of the subject of demographics. 

The temporal point chosen for this estimate, 18,000 YA, accomplishes three things that are required to increase the population estimate accuracy of a naturally functioning system with no anthropogenic in puts but is still similar to the 19th century's climatic conditions when the most pertinent field data used was gathered.   

Three Requirements   

1) 18,000 YA, is ~ 2,500 years after the accepted date for the glacial maximum, assumed in this research to be an interglacial period with climate somewhat similar to the 19th century with annual and seasonally ice-free land mass available to the Ivory-billed approximately the same 

2) 18,000 YA is before more than negligible anthropogenic effects on Ivory-billed numbers developed 

3) 18,000 YA meets prerequisites 1) and 2) and is as close as possible to 19th century condtions when the main population data was gathered

The temporal point, 18,000 YA is assumed to have had a similar climate, ocean level and seasonally ice-free summer land mass available to the Ivory-billed as was in the 19th century. By choosing 18,000 YA we matched as closely as possible the forest conditions of the three most significant studies of Ivory-billed population density. In general, these three forested areas were considered to have late seral forests with old growth characteristics similar to the habitat of 18,000 YA. Tanner, 1942 used "primitive" to describe these areas. 

Congaree National Park, NBP performed point surveys in over 30 locations

The compilation and analysis of direct observations and individual counts or surveys in determining population age structures and demographic trends is frequently used by land managers to address issues. This type of data is a basis for conservation and policy decisions hopefully leading to field management for the recovery of this federally endangered species. Rarely has the USFWS or its predecessors acted on reliable Ivory-billed sightings over 100 years; many seemingly plausible field reports were often rationalized into short visits to the site days or weeks later or inaction. Some detections caused J. Jackson, Mississippi State University (1970-99), P. Sykes, USGS or others to be dispatched or voluntarily get in the field but the design and effectiveness of their methods are questionable. Jackson and Sykes received tens of thousands of public dollars decades ago but there seems to be no publicly available reporting detailing methods and results. Jackson has anecdotal stories of possible Ivory-billed encounters but nothing detailing effective survey science; Sykes similarly hiked and boated around.   

Unfortunately, Ivory-bills do not aggregate in thermals, fall out spots, migratory stopovers or roosting sites. These phenomena have been used to help determine population size and the age structure demographics of birds with large but scattered metapopulations that are difficult to monitor. 

For species like the Ivory-billed the probability of detecting single birds or groups of birds by means of audio point surveys or visual surveys may be asymmetrical due to the specie's range of behaviors and/or habitat and topographic heterogeneity. To assess these potential biases, it is necessary to compare results obtained from various surveys with estimates derived from population models or idealized, comparative matrixes. These are possible future research topics.

To date, only four, liberally called surveys or population studies have been performed, due to the inherent difficulty in obtaining long-term population data for this and other long-lived vertebrate populations. These studies, Tanner, 1942, Cornell Univ./USFWS Arkansas Effort 2004 to 2006, Cornell Mobile Team ~ 2006 to 2008, and Virrazzi, National Biodiversity Parks, Inc. 2022 all detected small numbers of Ivory-bills.

Typical Point Survey Conditions 

These studies occurred after the Ivory-billed had suffered not only habitat destruction but also direct shooting for various reasons. C. principalis numbers were greatly reduced by the 20th and 21st centuries. These 21st century studies do give some limited, nuanced information about facultative habitat occupancy of the Ivory-billed 18,000 YA. National Biodiversity Parks, Inc (NBP) detected Ivory-bills in a variety of USDA forest types in three states. NBP by finding birds in different USDA defined ecological communities influences this research to assume occupancy in a variety of states and forest types of 18,000 YA. The Ivory-billed was likely not obligate to either conifer or deciduous forests; its modern preference for wet, seasonally flooded riparian habitats is a response to human predation of the Anthropocene which began ~ 15,000 YA.

Here are articles on some of NBP's field research:

SUMMARY NBP'S IBWO FIELD WORK

NBP IBWO STUDIES in CONGAREE NP

Obviously there were no surveys of any type done 18,000 YA; reliance on the various data gathered much later is temporally adjusted 180 centuries.     

  

This research may provide insight into how modern landscape-level simulations might eventually replace the historical estimates with more granular based ranges of possible Ivory-billed population sizes.

These maps or similar can be used to model improved granular population densities depending on variables such as forest type which each can be assigned, with ecological analysis, different population densities.

This map closely represents the amount of forest that may have existed 18,000 Years Ago

 

USDA forest type information can improve population estimate for the Ivory-billed

In this research the small number of studies together with anecdotal information strongly supported that C. principalis density had a north to south gradient which is to be expected for a species with nestlings that are obligate insectivores. This enforces known ecological drivers on population demographics of many species related to latitudinal, climate related clines (Hut, 2013) with actual observations of Ivory-billed population density. This supports the method of having two different bird densities based on the many biotic and abiotic characteristics latitudinal clines encompass, to more accurately model the Ivory-billed Woodpeckers' population.

The following estimated acres list is based on NBP's internal range map for each significant state's respective area that contained breeding or likely contained breeding IBWO's. It is assumed that 18,000 YA was an interglacial period similar to the 19th century today.  M equals a million acres in the list below. 

Included are several million acres of breeding habitat outside of Tanner's generally accepted historical breeding range map as the target time here is 18,000 YA. The geographical breeding range here is also influenced by writings of P. Kalm (IBWO seasonal to SW New Jersey in the 1700s inferring MD for this analysis), J. J. Audubon (states to Maryland in the 1800s, inferring NC and VA), T. Jefferson (places the species in Virginia inferring VA and NC) and Hasbrouck (historical range into central coast of NC).

Various references indicate that even in 1600 the Ivory-bills range was larger than this depiction.

The contemplation of range treatment here is subjectively weighed by the ecological impact and moderation of the eastern coastal plain's climate by the Atlantic Ocean's Gulf Stream compared to the cold winters of the Ohio Valley and other mid-west areas due to the plains affect.

MD 1 M 

VA 2 M

NC 5 M

SC 10 M 

GA 10 M

FL 40 M

AL 20 M

MS 15 M 

LA 30 M

TX 30

AR 15 M 

OK 10 M     

MO 5 M

TN 5 M

IL 2 M 

IN 1 M 

KY 3 M  

TOTAL 203 million acres

To estimate the carrying capacity for these two equally sized cohorts, north and south, we started with Tanner's summary (Tanner, 1942, pg 32) which is based on actual field work by himself and A. T. Wayne in the 19th and 20th centuries.

"This gives us three estimates of the abundance or density of Ivory-bills in primitive areas: in Louisiana, seven pairs in 120 square miles or one pair per seventeen square miles; in California swamp in northern Florida, about six pairs in sixty square miles or one pair per ten square miles; in Wacissa swamps in northern Florida, about twelve pairs in seventy-five square miles or one pair per six and a quarter square miles."

Two separate estimates of the Ivory-bills abundance or population density, one for the northern half of the total range acreage and one for the southern half are summated to obtain a total population number.

Conclusions

Tanner's and J.J. Kuhn's Singer Tract observations and density results is used for the N half of the Ivory-bills range. One pair per seventeen square miles is the estimated density for the N half of the IB's range. Each pair occupied 10,880 acres. The N half of the Ivory-bills range is modeled at 101,500,000 acres. 101,500,000 acres divided by 10,880 acres/pair = 9,329 pairs.

This equals 9,329 pairs x 2 = 18,658 birds

For the S half the two densities Tanner deduced from A. T. Wayne's field notes are averaged for the Ivory-bill from the two Florida areas; this results in one pair per 8.125 square miles. 

This equals 19,519 pairs x 2 birds/pair = 39,038 birds

Total = 18,658 birds + 39,038 birds  = 57,696 Ivory-billed Woodpeckers, estimated 18,000 years ago. 

The Imperial Woodpecker (IMWO) has a maximum historical population estimate of 8,000 according to the article: Status and conservation of old-growth forests and endemic birds in the pine-oak zone of the Sierra Madre occidental Mexico (1996). This reference reports the total species range for the IMWO was 39,920 square miles and each individual needed 13 square Km. Imperial Woodpecker Population Estimate

Considering the two congeners and adjusting for respective total species range in square miles yields:

IBWO   317,187 square miles

IMWO   39,920 square miles 

The range of the IBWO is 7.9 times that of the IMWO and the two species respective total population estimates are 57,696 vs 8,000.  The IBWO has 7.2 times the population of the IMWO in 7.9 times the area. This infers that carrying capacity of the two species per area is somewhat similar with the Ivory-billed needing about 10% more area per pair. 

The world's largest woodpecker is the likely extinct Imperial Woodpecker, which averaged 58 cm (23 inches) in length and is estimated to weigh over 600 g (1.3 lb). The Ivory-billed Woodpecker is  smaller, with a length of 50 cm (20 inches) and a weight of 500 g (1.1 lb).

C. imperialis is estimated to weigh on average ~18% more than an C. principalis inferring, an Imperial should need more area per pair if all other variables, besides weight, are idealized to be equal. An Imperial pair should need more area than an Ivory-billed pair.

Ecological success and species abundance is a correlate of a species' ability to persist through time and is driven by multiple factors that cause differential survival and reproduction. The abundance and density of congeners can be considered as a measure of ecological success between species.

The Imperial had pragmatically no large Picidae competitor as does the Ivory-billed in the Pileated. The Pale-billed Woodpecker was only marginally sympatric with the Imperial in Mexico. The trophic niche of the C. imperialis was therefore larger than C. principalis'; it has been observed to feed on fallen logs even at a time when sizable areas of large dbh trees were still found in Mexico. Horizontal, prone logs were a part of the forest strata they utilized. This microhabitat alone can account for a substantial increase for the Sierra Madre's forest's carrying capacity for a large and efficient Campephilus. 

A careful Bayesian analysis considering several major ecological differences would likely establish that the Ivory-billed may have had a density per area similar to the larger Imperial. The literature and examination of the ecology of the respective species is consistent with population estimates deduced here.  

As said the Imperial seems to have had a broader niche than the Ivory-billed. W. L. Rhien observed Imperials foraging on fallen logs in comparison to Ivory-bills (Tanner, 1964). This niche is dominated by Pileated Woodpeckers in the southeast United States.

Population estimates of 57,696 for IBWO and 8,000 for IMWO are not in opposition but confirmatory.

NBP during modern Ivory-billed studies employing advanced attraction techniques, accumulating data over 650 points from many locations. In a few forests, and from year to year, these locations supported the pair range estimate in this paper; NBP found that a pair of Ivory-bills could have a range of ~ 10,000 acres.  

Post-breeding population estimate for Ivory-billed Woodpecker:

Obviously total population of all species of birds is maximal right after the breeding season. Populations can literally double or more in a few months; the increase is due to eggs hatching and fledglings leaving the nests.

At the Singer Tract, Tanner and Kuhn reported observing 6 Ivory-billed nests which had 9 broods from 1931-39 (Tanner, 1942 p. 81). The Ivory-bill had 19 young leave the nest from 9 broods; this is 2.11 fledglings/brood. Three broods failed. This is direct Ivory-billed field data on success of their breeding phenology. This is a small location sample size (n = 1) however the data was accumulated over several years with several nesting pairs.  

Taking the above total pair number for the SE USA 18,000 YA we have 28,848 pairs potentially producing 2.11 fledglings per year per pair. This equals 60,869 fledglings.

Total population after breeding season is estimated at 57,696 adults plus 60,869 fledglings which equals 118,565 Ivory-bills.

On average these young birds will have a high mortality rate in their first year, while the adults will have a lower mortality rate. After the birds are fledged the total Ivory-bill population would have dropped until the next years breeding season due to natural mortality.

Ivory-billed nestling about 8 days before fledging 

 

Discussion

Modeling ecological characteristics of several different forest types in relation to an abundance or population density, could provide a more accurate estimate of the past IBWO population. There are five different major USDA forest types in the Ivory-bills habitat (see maps). The literature ranges within being adequate, uneven, silent or nonspecific on the relative carrying capacity and occupancy by IBWOs in these different forest types; however inferences can be made.

But better estimates are not a pressing conservation issue for the modern Ivory-billed; any additional justified variables will retain assumptions on the species demographic response to different woodland communities since raw data varies or does not exist for forests. The management of the Ivory-billed needs more attention.

Objectively, from the totality of the C. principalis reports, more southerly populations within the range were specifically highlighted for their relative abundance compared to all other areas (Tanner, 1942). This enforces known ecological drivers on population demographics of many species related to latitudinal, climate related clines (Hut, 2013) with actual observations of Ivory-billed population density. This supports the method of having two different bird densities based on the many biotic and abiotic characteristics latitudinal clines encompass, to more accurately model the Ivory-billed Woodpeckers' population.

Two separate estimates of the Ivory-bills abundance or population density, one for the northern half of the IBs range and one for the southern half of the total range are summated to obtain a total population number in those acres.

Tanner, used his own observations and others (J.J .Audubon, A. T. Wayne, et al.) to relate that the peninsular Florida, Gulf regions of the Suwanee River such as California Swamp, Wacissa wetlands, and Buffalo Bayou (present Houston. Tx area) had a relative abundance of Ivory-bills. These three areas are all in the southern half of the Ivory-billed's range as defined in this research:

Location --------------Latitude (S to N)

Buffalo Bayou-------29.7400373,-95.357490

California Swamp---29.7612452,-83.054545XXXX

Wacissa Swamps---30.237583,--83.984288

Singer Tract--------- 32.3016241,-91.9054949 

 

Tanner and his Cornell professors overestimated the amount of virgin forest in the Singer Tract; this infers the same forest, 18,000 years ago, may have supported more IBs than J. J Kuhn's Singer. For the N half of the IB's range the winters are colder and trophic resources available would have been reduced and less varied comparatively to the S half of the range. Intraspecific carrying capacity proportionally drops for more northerly latitudes for many semi-tropical and temperate taxa.

The two prior inputs or factors, one, underestimating the maximum carrying capacity of the Singer Tract by Cornell's/Tanner and, two, the decreasing carrying capacity with more N latitudes, are assumed to offset each other's carrying capacity impact for the N half of the IB's range. Further research into the differences in carrying capacity in relationship to latitude in a semi-tropical zone of North America will likely result in a better estimate of carrying capacity and population but any adjustments to the final estimated numbers should be minimal.   

Ivory-billed Woodpecker in cavity. Copyright to Academy of Natural Science VIREO

References 

Buckland, S. T., Studeny, A., Magurran, A. E., and Newson, S. E. (2010). “Biodiversity monitoring: the relevance of detectability,” in Biological Diversity: Frontiers in Measurement and Assessment, eds A. Magurran and B. McGill (Oxford: Oxford University Press), 25–36.

Matthew J. Ungerer & Matthew P. Ayres & María J. Lombardero (1999). "Climate and the northern distribution limits of Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae)" (PDF). Journal of Biogeography.

Boyer W. D. (1990). Pinus palustris Mill. Longleaf Pine, Pinaceae -- Pine family  Boyer

U.S. Fish and Wildlife Service. 200x. Recovery Plan for the Ivory-billed Woodpecker (Campephilus principalis). U.S. Fish and Wildlife Service, Atlanta, Georgia. 156 pp.

Hut R. A. (2013) 

Latitudinal clines: an evolutionary view on biological rhythms


https://royalsocietypublishing.org › doi › rspb.2013.0433

Lammertink. Status and conservation of old-growth forests and endemic birds in the pine-oak zone of the Sierra Madre occidental Mexico (1996). This reference reports the total species range for the IMWO was 39,920 square miles and each individual needed 13 square Km. Imperial Woodpecker Population Estimate



by · Cited by 239 — We review literature with respect to latitudinal clines



end of virrazzi  paper 

Pesticide

Pesticide

- Carbaryl

Bifenthrin

Permethrin

Raw Data 

Beavers---to Fv  trapping significant before 1800



Probably because of their feeding and breeding dependence on large old trees, great slaty woodpeckers are most common in primary forests and show density reductions of over 80% in logged forests.[6] The global population is in decline because of the loss of forest cover and logging of old-growth forest throughout its range, with habitat loss being particularly rapid in Myanmar, Cambodia and Indonesia which are the countries that still hold the majority of the global population. In 2010, the great slaty woodpecker was included in the IUCN Red List in the Vulnerable category.[1]




We conclude, first, that spatial scale has indeed had an important effect on the characterization of the Panama bird community. The intrinsically patchy distributions of most forest-dwelling bird species raise the need for large-scale censuses. Second, the Panama community, compared with the two Amazonian sites, has a fundamentally different organization; it hosts nearly twice as many individual birds and is distinctly less dominated by rarity. Similar patterns of community structure appear to be present within tree and mammal communities as well. Therefore, results from the Amazonian studies cannot be generalized to all lowland Neotropical communities. We attribute differences in community structure primarily to differing biogeographic histories. The lower species richness and the greater number of total birds present in Panama appear to derive, at least in part, from two important factors: an area effect linked to the location of Panama on a narrow isthmus, and the repeated history of disturbance on multiple temporal scales in Panama.

FB 9/12/22

Modern Carrying Capacity--Why the Low numbers-Critical Topic

Someone asserted there may have been 500,000 IBWO at one time. This is a high number, only possible if we do not agree on the probable or actual niche then. An unrealistic broad niche, drastically exaggerates derivatives like pre-contact, 1930's, and modern population numbers and carrying capacity. My early draft pre-contact number is 150,000 birds. (Today there may be 1.9 million PIWOS and their peak could have been 25 million birds).

PIWO may have 150 times the popalation of IBWO at one time; in the SE USA the ratio would been much less elevated.

Since this is a critically endangered species, actual niche and modern carrying capacity should be carefully discussed. Taking acres of land from 1800 via time tunnel and doing a simple acre to acre extrapolation, with today's low quality forest, small linear patches, and loss of genetic viability is the raw material that leads to an unrealistic, unfounded and likely erroneous modern carrying capacity numbers.

Today we have a somewhat stabilized acreage number in some areas of very slowly increasing DBH forests. Good ecological news seems to end there. Linear shaped acreage linking these areas is under pressure and these greenways are slowly to quickly, being destroyed.

Historically we have a small fraction of the original acres this species occupied, remaining forest is mainly mid-seral, fragmented habitat, greenways being attrited, global warming causing unknown and known ecological asynchronicities (diseases spread/mutate faster, invasive species in the hundreds. unprecedented destruction in the batture forest, light pollution adversely affecting coleopteran biomass, feral pigs driving snakes into canopy eating birds/eggs, known inbreeding by 1905 and much more).

Field reports are basically disappointing. The preprint paper reporting on 3 birds in LA 2019 dropping to one or two birds that dozens of people have encountered over 15 years in the same general spot. It's a small number of birds seen infrequently in a large area that have been reported over and over.

Older references point to IBs reaching highest numbers in large scale, forest mosaics of upland pines (prone to burn) with interdigitized forest bottoms (do not burn; low food for nestlings, but good for nest location due to water at base of tree). This optimal habitat landscape is basically gone in the SE USA, without basic management.

The IBWO's niche likely was and is forest areas with the highest 2-3 year post senescent standing deadwood. Fires, hurricanes, beaver, etc provided that. As the concentration of this age cohort of substrate drops carrying capacity drops below support level, as is the case in most modern areas. As the species was forced back into more inaccessible areas (forest swamps, bottoms, batture forests) it's faced with foraging in forests that have less 2 year dead wood than it needs to consistently fledge even 1 bird/year let alone 3.

Its forced to excavate (time consuming, increased time from nest) rather than the more efficient scaling; it has a morphological and behavioral advantage and predilection to scale recently dead wood.

Behaviorally the modern IBWO is not the same as the precontact animal. Due to nominal microevolution caused by severe and persistent anthropogenic taking of the least wary bird (subsistence, museum, and curiosity hunting) the bird now instinctively is "hard-wired" to prefer the most secluded section of forest which may be far from quality feeding areas for themselves or nestlings. Today the habitat landscape is dominated by short to longer, narrow river forests. The IBWO being instinctively fearful of people results in it foraging away from habitat patch/forest edge as you would if you instinctively were programmed to avoid, for example lions, which are in the fields and shade of the forest edge and they will kill you. So the aerial of a 10 mile long and 1 mile wide river forest habitat may seem to be 10 sq miles but an IBWO may perceive it as only 5 sq miles further reducing carrying capacity.

Finally the IB was already showing a loss of genetic variability before 1900. It's likely that there is some increase in embryological or hatchling mortality via various genetically based mechanisms that have increased the chances of homogygosity of deleterious alleles.

Our science based surveys lasting months camping located several birds over many years. However in only one high DBH forest did we surmise the density of a pair in ~ 6K acres. Overall we encountered only 0 to 1 bird every 30K acres covered at locations that some would call good habitat by basic assessment, but not necessarily one we agree is optimal without management or fire (to increase deadwood/concentrating beetle larvae reducing nest predation).

Tanner stated pg 32 or 33 that the maximum IBWO abundance was one pair in 6 sq miles (4,000 acres). This max estimate were from forests long gone; replaced with houses, or at best substantially lower quality habitats in many, many ways. Mid seral or even older forest likely do not have enough substrate for a strong species recovery and maybe any recovery. Management may be the only hope. This is independent of how many pictures we have or do not have.

Regardless ecology is complex; the IBWO has somehow persited, microevolution is rapid and things can by definition change rapidly for the better.

 A few years later, James Tanner began a study of Ivory-bills as part of his Ph.D. dissertation and eventually wrote an in-depth report, funded by the National Audubon Society, that was later published as The Ivory-billed Woodpecker. His report estimated that only 22 to 24 of the birds remained in the United States.    

Population number

According to the IUCN Red List, the total Ivory-billed woodpecker population size is fewer than 50 individuals and mature individuals.

This picture has been disputed by Noel Snyder, who contended that hunting rather than habitat loss had been the primary cause of the population decline. He argued that Tanner's population estimates were made of an already depleted population, and the home range needs were significantly smaller.^[48]

Records exist of the ivory-billed woodpecker farther north along the Atlantic Coast; Thomas Jefferson included it as a bird of Virginia in Notes on the State of Virginia, where it is listed as the "White bill woodpecker" with the designation of Picus principalis.^[41][42] Audubon reported the bird could occasionally be found as far north as Maryland.^[43] Pehr Kalm reported it was present seasonally in Swedesboro, New Jersey in the mid-18th century.^[44] Farther inland, Wilson reported shooting an ivory-bill west of Winchester, Virginia.^[39] Bones recovered from the Etowah Mounds in Georgia are generally believed to come from birds hunted locally.^[35] Within its range, the ivory-billed woodpecker is not smoothly distributed, but highly locally concentrated in areas where the habitat is suitable and where large quantities of appropriate food may be found.^[28]

 An internet post on Facebook (4/29/22 below) guessed that there was 500,000 IBWOs at one time or perhaps circa 1800.  

George DeBusk

Tanner found home ranges of 1500 to 3000 acres in the Singer Tract, versus 40-50 for a Pileated pair in good habitat. It could be the Singer Tract birds were way below carrying capacity and therefore had large ranges, or it could be they really need that much space as they are, during breeding season, pretty much a specialist on boring (generally Cerambicid) beetle larvae and that is a pretty scarce resource (maybe patchy is a better descriptor than scarce). The Pileated, being more of a generalist and able to eat a wider variety of foods can subsist on a smaller territory (I have seen huge dead pines nearly cut in half by Pileateds searching for carpenter ants, for instance).

There are about 11,000 acres of old growth (not necessarily Virgin, just old growth) in Congaree NP. That would, in theory, support 3-6 breeding pairs. That is just the largest area of old growth. A place like the Choctahatchee or the Apalachicola bottoms in the FL panhandle might not have as much “old growth” forest, but still would have the type of dead and dying trees that provide food for the IBWO. There are probably close to 100,000 acres of older secondary forest in those two river systems. If they had territories at the higher end there you could easily accommodate 15-25 pairs if at capacity. White River NWR in AR has 160,000 acres, much of it very advanced second growth if not old growth. What would capacity be there? Maybe 40 or more pairs? There are dozens of other places with large enough areas of older growth to support one pair or multiple pairs - the lower Santee, the Savannah, the Altamaha, Okeefenokee and environs, the Green Swamp of FL, the Pearl, the Achafalaya, Tensas NWR, Big Thicket, etc. if they survive and can persist in second growth forests, there are probably well over a million acres of potential habitat. Carrying capacity? Who knows, maybe 200-300 pairs?

Compare that to the days of Wilson or Audubon when just the Mississippi Valley had tens of millions of acres of old growth. I would guess the original population, particularly if it sustained the kind of trophy hunting described by Audubon and Wilson, must have been at least in the 500,000 range (that is just a guess without any calculations behind it!).