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!).

Ivory-billed Woodpecker Wingspan and Body Length Measurements and Species Discussion, Drone Footage LA

 

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. 

------
  

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

Have found more ecological correlates that support the landing tree height is indeed in the 90 to 105 foot range. That height was used in this article to deduce a length and wingspan of the "drone bird".

I have researched the maximum heights of the common tree species in the area and looked at age of the trees in that area against minimum growth rates to establish a minimum tree height.

Also you can see in the video that trees of seemingly same species have varying DBH in the scene. The highest DBH trees and obviously likely the oldest have heights that are not much more than the smaller DBH trees. This indicates that these individual trees have more secondary growth than primary growth (vertical growth) which occurs when trees are older and can be approaching 90 feet or more depending on species.

I am highly confident that the estimates of wingspan and length are close (below)_and this bird is Surely not a Red-headed Woodpecker. Color fidelity in the video is sufficient to say this is not a PIWO. The last species choice is obvious.

But still like to see more about camera specs. end 9/11/22 comment Virrazzi

High Detection Rate of Ivory-billed Woodpeckers in Congaree National Park, SC 2006 to 2009 Indicated Presence

 High Detection Rate of Ivory-billed Woodpeckers in Congaree National Park, SC  2006 to 2009 Indicated Presence  

copyright-Fred Virrazzi

There have been numerous reports of Ivory-billed Woodpeckers in South Carolina subsequent to the last accepted Singer Tract sighting (1944). The Palmetto State sightings were made by many excellent birders, rangers, hunters, naturalists, scientists and citizens.

In 2007, 2008, 2009 and 2011 National Biodiversity Parks, Inc. (NBP) researched, under various federal permits, attraction of Ivory-billed Woodpeckers during Point Surveys in South Carolina. Our field personnel had multiple Ivory-billed Woodpecker (IBWO, IB) detections in multiple years of the 4 field years in SC. These detections included a sighting, a kent, single knocks and  double knocks reported by experienced personnel. 

From 2006 to 2008 various additional formal surveys were performed by other entities and individuals under the umbrella of the South Carolina Ivory-billed Woodpecker Working Group (SCIBWWG).

Over the 4 subject years, 60 or more Ivory-billed reports came from the same ~ 26,000 acre park where NBP had multiple encounters during our research. There is latency for Ivory-billed reports going public due to various formal agreements; it can take many years for researchers to recognize that sightings were tempospatially related. The latency is partially by design.

For the first time, all the Ivory-billed, human detections that the author is aware of is summated in this draft table:

There were also several different IBWO detections by ARUs; these recorded kents and DKs. The ARO detections are not included in the above table but the SCIBWWG summary paper seemed to highly rate these as IBWOs or likely IBWOs. 

There was an unprecedented number of Ivory-billed Woodpecker detections in this one, 26,000 acre park in SC from 2006 to 2009 rivaled only by the Singer Tract, LA after 1900.

This is an incredible number of human detections; no other area post 1944 has 67 detections claimed in any 4 year period. There is likely no single location in the last 75 years with 67 detections let alone 4 years.

At the Singer Tract, from 1941 to 1944 there were likely more than 67 detections claimed as the previously large forest area was attrited, one or more birds lingered and the last birds were somewhat acclimated to tract caretakers. The one, two or more birds there those 4 years were repeatedly seen over and over sweilling the detection number. Congaree (CNP) birds are comparatively harder to see in my experience yet there are many modern sightings.  Without a full tempospatial analysis of these 67 detections it is impossible to say if more than one or two IBs could have been involved.  The SCIBWWG was evidently disinterested in any mapping or statistical analysis of this unprecedented number of sightings.     

The details of the 67 Congaree detections are poorly described and exceedingly vague in the SCIBWWG's final report. 

IBWO Final Report SC

This summary work is done by committee, seems rushed and forced and lacks basic scientific information after mostly volunteers donated several thousand hours of assistance to the group and indirectly the government. Every sighting is only described as "brief" and some of those a "brief fly by". Brief is then never defined in the report. Two sighting may or may not be flybys; the paper is unclear. These 9 sightings demanded more granularity.

As Ivory-billed researchers and literature readers know skeptics have called the 10 minute long, very close Kulivan sighting of a pair of Ivory-bills "brief" (1999, Pearl River, LA). The sighting of a pair was for 10 minutes; this is not brief. Subsequently there were many sightings in that area with supporting video of an IBWO. Kulivan and his sighting were considered reputable; he was on the IBWO Recovery Team Committee.

Rarely has such an inadequate, casual treating of 9 sightings of an uncommon species let alone a species that is considered critically endangered been presented.

Here are the four sentences on the 9 sightings:

"In addition to acoustic encounters, a few visual encounters were reported from Congaree National Park, although all were brief views by single observers. These visual encounters did not provide enough diagnostic field marks to completely rule out other species. In Year 1, four observers reported 7 visual encounters, all of which were brief fly-bys. In Year 2 and 3, single brief visual encounters were reported."


Regardless there are other numerous data sets in the summary paper that strongly support the presence of IBWOs in Congaree if properly interpreted with plausible explanations.

For example, the final report's explanation of the acoustical detections of double knocks as possible duck wings striking, gunshots or Pileateds are implausible and unacceptable to this researcher. The IBWWG also considered some these skeptical explanations unlikely. More information from the past notes and present field (2022) is needed. 

Also, it is unexplained how the report's authors determined there is "likely no breeding population" in Congaree with the 67 detections in Congaree but substantially less in other large open spaces of SC. "However, we believe it is unlikely that a population of Ivory-billed Woodpeckers persists in Congaree National Park due to the absence of firm results despite persistent search efforts for 3 years."

Congaree has superior IBWO habitat to all those other areas. 

Many ecologists use source-sink population models or equivalent to make conservation decisions. There is not a mention of which, if any, assumptions, methods, formulas, theories, models, etc. were utilized to clarify there is "likely no breeding population" in Congaree National Park. 

Source–sink dynamics uses variation in habitat quality to hypothesis on population dynamics. NBP has ground assessed key IBWO habitat in three states. Congaree is superior to any remaining similar sized area in the SE USA.  The COWASEE Basin (see following map) which includes Congaree NP also has some comparative carrying capacity to any similar ~ 200,000 acre area in the SE USA. 

Ivory-bills are noted repeatedly in the literature as being very wary and quiet around their nests. There is no indication that the SCIBWWG designed its effort tempospatially to find nests or seriously research carrying capacity. There is no basis for the SCIBWWG to have concluded Ivory-bills are likely not breeding in the park; the evidence and source-sink dynamics actually strongly supports the possibility of breeding. Obviously more study is needed.               

The results from SC indicate Ivory-billed presence. Repetition of IB detections in one location has often been denied by individuals and departments to have occurred, but serial Ivory-billed encounters has happened. Sightings, kents, double knocks and single knocks, collectively encounters, have been repeated in various SE USA locations besides the one described here.

In 2022 it again became obvious to a very few that two totally unconnected Ivory-billed search efforts had detected the species at least 3 times in the same localized section of the large park in 2009. A third party, a SC resident (G. DeBusk), hearing of the initial two person sighting report, including an avowed skeptic, hiked towards the sighting location. He viewed an Ivory-bill accompanied closely by a similar bird (probable IB pair) in the same exact area a week after the seminal event. He also found dead wood, insect working, immediate to the location of where the IBWO was first acquired. He considered the excavation highly indicative of Ivory-billed based on his past Congaree research.


In 2009 our team, during 7 days of wilderness camping and workman-like point surveying, heard a kent, a double knock and had an IB sighting. The sighting was punctuated with a subsequent double knock using the specially designed Point Survey method.

These three disparate parties had four IBWO detections with two not following or privy to each other's reports or locations; they were unaware of the others exact location within the park during the respective prior efforts. As mentioned another party, G. DeBusk, followed the fresh IB lead.


In science the more times independent experiments or studies are repeated with the same results, the more likely the conclusion is accurate. In statistics, replication is repetition of an experiment or observation in the same or similar conditions. Replication is important because it adds information about the reliability of the conclusions or identifications drawn from the field observations. The statistical methods that assess that reliability rely on replication.


The probability of the NBP detections being a purposefully attempt to mislead, assuming they occurred within the 2 mile square area that includes the seminal sighting can be examined by inferential statistics as follows:

Notes: All 3 detections were in an ~ 2 square mile area. A 2 square mile area is 1.41 mile by 1.41 mile; this is 1/20 of the 26,000 acre park.


Since all three detections were made in ~ the same 2 square mile area, the chance of correctly or randomly picking the area to agree with the prior sightings to better stage contrived detections would be 20 squared, = 400 to 1.


The three separate 2009 Ivory-billed Woodpecker detections that had no knowledge of each other's search location data are as follows:


Detection 1 2/7/2009 Fran Rametta, a NPS ranger along with Corinne Fenner, we’re leading a guided canoe tour.

Saturday February 7, 2009


1:30pm, sunny, 70 degrees


Corinne Fenner and Fran Rametta were leading a guided canoe tour and spotted a very large, chunky bird. It was dark colored and flitting from tree to tree after flying up from near ground level. As it was flying among tupelo trees, we saw a distinct line of white feathers along the back of both wings. There was a black line along the front of both wings. The bird was silent. This sighting lasted approximately 6 seconds. Please see attached map.
(exact author unknown to author but is not either sighters'). and 

"Fran was a jovial skeptic, so the change into an equally jovial believer was fun to witness." (Hunter, C. FB public comment 6/2022). Fran may be retired now (7/22, Virrazzi). Location - Cedar Creek

Detection 2 10/2009 NBP's permitted team had a three person detection within ~ 1 mile of Detection 1. A loud, agitated kent was heard by the entire team. (See official USFWS IBWO comment letter from E. DeVito below). Formal online reports were given to the required and correct jurisdiction; they are password protected with lead researcher access (Virrazzi). Immediate field notes were made and are as of 7/22 unpublished.

Detection 3 10/2009 A few days after Detection 2, NBP's team was hiking east to a survey point when the author saw a largely white-winged, dark bodied bird the size and shape of an Ivory-billed fly from the assumed base of tree surrounded by water. The bird was only ~ 150 feet away, eye level and no take-off disturbance rings were observed, meaning it was not sitting in the water before flushing. The park's ground is very rough and noisy; our team members are directed to space themselves 20 feet apart when we are hiking from survey point to survey point so researchers can better hear any ambient single knocks (SKs), DKs or IB kents. I was not able to get any team members on the bird or raise my binoculars because of the shortness of time in view and the high basal area in this late seral forest.

The team then did an unplanned, permitted ADK survey point at the spot starting several minutes later and had a response DK from a few hundred yards away within the post ADK designed survey waiting period (20 minutes), (see official USFWS IBWO comment letter from E. DeVito below). Formal, required computer reports were given to the correct jurisdiction; they are password protected with lead investigator access (Virrazzi). Immediate field notes were made and are unpublished as of 7/22.

Related Congaree NP Detections that have some details (there are many detections whose details are unknown to the public):


2007 - NBP an incredibly loud, Single Knock of an IBWO was heard ~ 2.5-3 miles S of Detection 1 in 2009 above.

2007 - Cornell University Mobile Ivory-billed Woodpecker Search Team effort. An Ivory-billed Woodpecker responded with a single double knock (DK) to a mobile team's anthropogenic double knock (ADK).

2008 - NBP Multiple single knocks were heard in an area within 1-1.5 miles of Detections 1-3

2/16/2009 George DeBusk, sighted a pair of Ivory-bills within 150 yards of the Detection 1 sighting location several days earlier; he was searching the park because of it. DeBusk is a highly regarded SC citizen with a formal zoology background. By the time of the sighting, he had been searching for the Ivory-billed in the park several times before.

Based on public information in the SCIBWWG's summary report and knowledge of NBP's and others' efforts, it is estimated that 10,000 total field hours were spent; this is one detection per every 149 field hours. In NBP's extensive experience in the field and reviewing modern literature and postings this is a high detection rate per time effort. NBP had an ~ 100% higher detection rate per field hour in Congaree than CLO efforts with different methods.

In NBP's studies this detection rate per hour for NBP is only exceeded at two other SE USA locations. At both those locations substantial evidence of IBWO presence was eventually made public by various researchers.

In general, the photographic possibilities for capturing an Ivory-bill in the Congaree are significantly reduced compared to most other areas because of the topographic conditions, lack of many canoe navigable waters in the forest, mostly wilderness conditions (few trails, noisy to move), superior canopy of 30 to 40 m, causing darkness, high DBH trees and basal area resulting in a dense mid and upperstory, and more.

Any careful Bayesian statistical analysis of Congaree's 67 IBWO detections will come up with a high probability of one or more IBWOs being present in Congaree from 2006 to 2009. 

We recommend that the USFWS review the extensive evidence presented here and the original detection, sketches and recording in all the other federal and state govt. files before determing IBWO presence. 

Regardless the evidence summated in this article, and NBP's USFWS presentation today does not support the extinction of the IBWO in SC.

Acknowledgements to E. DeVito, T. Haydu, L. Shaw, T. Thom, P. and J. Dubois and others for field survey assistance and support in SC.