Hypothetical IBW survival question.

[gws]

I'm not a biologist or scientist, but would like some thoughts based on the following scenario. Please humour me, I'm just trying to get a feel for the outlook for the Ivory-billed woodpecker.

Let's suppose there are 5 breeding pairs of IBWs in Arkansas, and maybe 5 to 10 pairs scattered elsewhere in Louisiana, Mississippi, and E. Texas, all states that adjoin Arkansas. Would this be enough of a start to slowly build the IBW
population up to a viable level, ASSUMING the birds are left alone and that suitable habitat slowly increases, or is the IBW inevitably doomed in this scenario because of the ramifications of "genetic impoverishment"?

I sure hope and pray the lord god bird makes it...any opinions on the above scenario?

[alcedo.atthis]

"Please humour me, I'm just trying to get a feel for the outlook for the Ivory-billed woodpecker.

Let's suppose there are 5 breeding pairs of IBWs in Arkansas, and maybe 5 to 10 pairs scattered elsewhere in Louisiana, Mississippi, and E. Texas, all states that adjoin Arkansas. Would this be enough of a start to slowly build the IBW
population up to a viable level, ASSUMING the birds are left alone and that suitable habitat slowly increases, or is the IBW inevitably doomed in this scenario because of the ramifications of "genetic impoverishment"?

I sure hope and pray the lord god bird makes it...any opinions on the above scenario?"

There would be so many potential interferences, it's hard to say.
Predation, food shortages, habitat suitability, disease, infertility, weather, "genetic impoverishment", etc, etc, and do you really think that man would leave them alone??
Man has interfered with other species in the past, (Nene Goose for one) with varying results.
http://www.wwt.org.uk/threatsp/pastwwt/nene.htm
Nature is never cut and dry.

Regards

Malky

[Tom c]

Yeah your right there natures never simple!i think the main problem facing them if they increase would be a small gene pool leding to a bottle neck in the population!the limited gene pool may lead to interbreeding and problems related to that!but with any hope theres enough of them to withstand that pressure!good luck to u birders in the U.S.

[Tim Allwood]

main problems facing the bird according to the IUCN / BirdLife are:

D1 (CR) which means a population of feweer than 50 birds

and

D2 which means a very small range <100 km2 or 5 locations

logging and cearance for agriculture are responsible for the dramatic decline in numbers and range and these factors are likely to threaten any remaining population

hope this helps
Tim

[fangsheath]

The answer is not necessarily. We simply do not know how vulnerable this species is to inbreeding and small population genetic effects. But we have good reason to hope. For one thing, many laypeople overestimate the vulnerability of species to genetic bottlenecks. It is mainly species of mammals that form herds that display reduced viability after a relatively few generations. The commonly used population criterion of 200 adults for long-term survival is almost surely an overestimate for most species.

In the case of this species, what we know about their natural history suggests low vulnerability to small population genetic effects. They had low population densities and were not colonial nesters. They have fairly specific habitat requirements which probably limited genetic exchange between large floodplains. Although there has been some suggestion that they are "nomadic," it seems likely that under presettlement conditions established pairs would have stuck to particular areas.

The mere fact that the species has survived this long is probably a fair indication that they can persist at very low population levels. The trick now will be to get population data, and hopefully genetic samples, without interfering with the birds. This is not a California condor, soaring in plain sight, that we can readily bring into captivity and raise. It will be a tremendous challenge to even find these birds, much more so to get genetic samples, without adversely affecting them. However, some of our best, brightest, and most dedicated are on the job. The ivory-bill has demonstrated that it will not give up so easily. And we have learned our lesson. We will not give up on them.

[GreatHornedOwl]

Can large woodpeckers actually be kept & bred in captivity ? Seems difficult to me ! Otherwise something along the lines of the Whooping crane project would have been a possibility.
I think the key here is to secure as much good habitat as possible. If the species survived up until now, it sure has some resilience, and a chance of survival if it has enough habitat.
Tanner examined the genetic question, and I believe he concluded that 22 birds was enough, provided that enough primeval wood was spared.

[Tim Allwood]

okay

the number of 50 individuals used by Birdlife / IUCN comes from early studies in 1980 by someone called Fanklin using domestic animals - research since has gone the other way and the situation is now described by the 50/500 rule - research now shows that a min. of 50 birds is needed and preferably 500 to maintain genetic variability

in some studies a population of fewer than 8000 (!!!) leads to a loss of genetic variability

A specia category of bottelneck is called the FOUNDER effect where an individual or two leave a popuation to start another one. Here a founder size of 10 is needed to maintain 90% of the variability - fewer than 10 and it drops of frighteningly quickly

problems associated with small pops that take more time to go into are
inbreeding depression
loss of heterozygosity
genetic drift
unequal sex ratio
outbreeding depression - mating between individuals of genetically differing pops

and imprtantly the ALLEE effect - animals in widely dispersed populations may be unable to find a mate

Tim

[fangsheath]

Indeed, but let's be clear that "loss of genetic variability" does not equal extinction, particularly on a time scale of a few generations. Cheetahs have low genetic variability, but cheetahs are still with us. If the White/Cache River population of ivory-bills is isolated (which I think is likely), it may already have low genetic variability. But that doesn't mean it's on its way out! Furthermore, within 30 years I expect our understanding of genetics and development to improve to the point that we can counteract these effects. We might even be able to obtain genetic material from museum specimens and at some point begin to rebuild the genetic diversity of the species. And I fully expect that other populations of ivory-bills still exist. We have every reason to hope that the ivory-bills will continue to be with us. But it will not be easy.

[Tim Allwood]

Hi

I'm not suggesting losing genetic variability = extinction just that there are several very real problems associated with very small populations and that IBW will not be immune from them

1500-5000 cheetahs remain
interestingly four other species in the same genus Acinonyx actually went extinct in the pleistocene, presumably as they fragmented into small pops

cheetahs now only have 10% of the sperm count of related felids and 70% of their sperm are aberant in some way.

this lack of variability makes them unusually vulnerable to disease, meaning they could crash at some time in the future.

we need a long term view - which is why it's so important to stop other species worldwide getting into the situation of the Ivorybill. I'm not comfortable with taking genetic material from museums at all... it can be seen as an 'easy' option making it less important to take care of small remaining pops of wild organisms

[Field Sparrow]

Interesting subject. I think so little information is out there concerning the ivory-billed woodpecker, or any woodpecker species for that matter, that it is hard to say how many individuals are needed to keep the ivory-bill from becoming extinct. Looking at some other American bird species that almost became extinct we find the Kirklands warbler in the early 1980s with only 200 some males (during the singing male census). Now we see (once the prescribed burns of the jack pine were started) it numbering almost 2000 total birds. Another success story is the whooping crane. If I remember my readings correctly, wasn't it down to just 17 birds in the mid-1940s? Once the captive breeding crane project was started, we see their numbers have increased too. Isn't it something like 200 birds now? And they have a Florida group going! I remember seeing pictures of the birds following the ultra-light plane during their migration lessons. And the ever-popular California condor. It was down to under 30 birds in the mid-to-late 1980s and with that captive bird program we see released condors reproducing once again in the wild. Getting away from the aves, other examples are the American bison and black-footed ferret. There was just a handful of each. Now there are thousands of bison. I'm not sure the status of the ferret; I think its several hunderd.
These species are back, some more than other from the brink of extinction. With protection, especially habitat, I think the ivory-bill will hang on, perhaps increase. But I feel we are going to need large tracks of undisturbed southern bottomland forests for it to do more than just hang on. I'd be very hesitant to try a captive program with the ivory-bill. It's held on for 60 years here without being seen. I think giving it the habitat to survive is better than taking a chance capturing what few may remain and hoping they will reproduce in captivity. Genetically, I don't know what effect inbreeding will have on the ivory-bill (or any of the species I've mentioned above). We'll just have to do the best with what ivory-bills remain. Indeed, perhaps the important lesson here is to not let any species drop to such low individuals that we'd have to worry about genetics. And that will be hard to do considering the present administration in Washington!

[Tim Allwood]

incidentally 300,000 acres of contiguous forest remains or 1214 km2

of this 220,000 is potentially suitable or 890 km2

minimum territory size is i think about 16 km2

you can do the maths!

Tim

[Field Sparrow]

I wonder if they will do some selected "ringing" of live trees in the ivory-bills' Arkansas home area? From what I've read, the ivory-bill seems to perfer grubs under the bark of certain trees, especially sweet gum. Also from my readings I see where those grubs perfer trees that have been dead just 2 or 3 years. Past that time, its not ideal habitat for the grubs, thus less food for the ivory-bill. With selected "ringing" of trees, we could "help" supply the ivory-bill with more feeding opportunites. Every year, deaden some trees to keep a fresh supply of the proper grub habitat. Does this seem a good idea?

[Tom c]

Agree With you on this one Tim low levels of habitat has to be a serious issue!and no matter how few individuals are left natural instinct is that they will interbreed if no other suitable mate is avaliable!

Interbreeding might not mean exstinction but it would reduce the restistance to disease and fertility.

[fangsheath]

I think that is a possibility, although I have no doubt they will proceed very cautiously with any habitat manipulations in the White/Cache system. The first step will be to obtain as much data as possible on the birds so that we can more clearly understand what their needs are. That will undoubtedly take a good deal of time, and I don't think any manipulations will be in order meanwhile. And of course the first priority should be to protect more habitat, and continue restoring clearcut areas.

[Rasmus Boegh]

is the IBW inevitably doomed in this scenario because of the ramifications of "genetic impoverishment"?

What you refer to as "genetic impoverishment" is poorly understood. The most extreme example may be the Black Robin from New Zealand. Today the population is above 250 and they seem to be doing relatively fine, but in 1980 there only were 5 (!) birds left, of which only one was a female. Every single Black Robin that's alive today are descendents from a single pair, a female named "Old Blue" and a male named "Old Yellow" (after the colour of the ring they had on their leg). Why this species seem to manage and hasn't deteriorated completely due to a lack of genetic diversity is an open question, especially as other species have done far worse even if their initial populations was far larger. We can only hope the Ivory-billed falls into the category of species where a lack of genetic diversity for some reason doesn't seem to hit as hard.

[gws]

I wonder if they will do some selected "ringing" of live trees in the ivory-bills' Arkansas home area? From what I've read, the ivory-bill seems to perfer grubs under the bark of certain trees, especially sweet gum. Also from my readings I see where those grubs perfer trees that have been dead just 2 or 3 years. Past that time, its not ideal habitat for the grubs, thus less food for the ivory-bill. With selected "ringing" of trees, we could "help" supply the ivory-bill with more feeding opportunites. Every year, deaden some trees to keep a fresh supply of the proper grub habitat. Does this seem a good idea?

I think girdling or ringing of some sweet gums and nuttall oaks in order to deaden them may well be a good idea. I wouldn't just do it in the immediate area where IBW was rediscovered, but spread it out a little.

What I would do, if I had a say, would be to establish as many refuges as possible on both sides of the Mississippi River in Arkansas, Mississippi, and Louisiana and try to connect a Corridor of Hope all the way from the Cache River/WR areas in Arkansas clear down to the Atchafalaya Basin in Louisiana.
I would also reassure the hunters in these states that their ability to hunt their ducks, deer, etc, in these areas will continue. I would involve hunter groups and educate their various associations about the IBW. Get them involved. I suspect they would take an interest in the plight of the bird. They have tremendous political clout in these states, and their dollars could help in establishing more and more protected land that would help them also.

I am a little leery of the "expert" types (the same ones who considered the IBW extinct) coming in and adversely effecting the remaining populations of IBW by overmanagement. In short, restore as much habitat as possible, connect the corridors, and largely stand back and hope.

[Rasmus Boegh]

I am a little leery of the "expert" types (the same ones who considered the IBW extinct) coming in and adversely effecting the remaining populations of IBW by overmanagement.

Can you mention a single case where "expert types" overmanaged a species to an extent where they were to blame for an extinction? I'm not saying it hasn't happened, just that I can't remember a single case where it did and would be pleased to be pointed in a direction if you know of any...

[Tim Allwood]

lets not start knocking the experts...

the categorisation of IBW had been thought about long and hard and is 'possibly extinct'

remember despite extensive searching, still probably only one individual has been located.

I put my faith in those folks at Cornell / BirdLife etc. They do know what they are doing

Tim

[Field Sparrow]

I agree with gws. Sometimes we humans can "love" something to death. Since all we really know about the IBW is the work that James Tanner did in the 1930s, the best I feel we can do is to protect the bird's habitat. Selected girdling of sweet gum and nuttall oaks (thanks gws, I'd forgotten the other important IBW feeding tree) and then stay back. GWS brings up a good point on getting others involved. If total hunting and fishing is banned in Arkansas' IBW areas, then we will lose much needed support (here in W. Va., gun owners are 3rd in political clout, after Jesus and Robert C. Byrd). The hunting/fishing may have to be limited; such as only so many in at one time. I also see nothing wrong with limited birding on the outer fringes of the birds feeding area. Many birders want to see this bird. The chances of seeing the bird here will be almost 0%, but these visitors to the area will play an important part. By spending their money on hotels/motels, gasoline service stations, restaurants, etc., the local people will see the economic value of protecting the IBW. Of course, the breeding/nesting areas should be off limits to all, except the "experts" working on compiling information. And if the "experts" are smart, they will include some birding "laymen" with their research. More can be gained by including us than by excluding us!

[TexasFlyway]

incidentally 300,000 acres of contiguous forest remains or 1214 km2

of this 220,000 is potentially suitable or 890 km2

minimum territory size is i think about 16 km2

you can do the maths!

Tim
What are you referring to here Tim? The area in Arkansas ?

[Tim Allwood]

Hi Tex

Yes

[GreatHornedOwl]

incidentally 300,000 acres of contiguous forest remains or 1214 km2

of this 220,000 is potentially suitable or 890 km2

minimum territory size is i think about 16 km2

you can do the maths!

Tim

I think it was 16 km2 in the Singer Tract in 1939. It also depends on the number of suitable (dead) trees for food, if I'm correct ?

[fangsheath]

Yes, the Singer Tract was considered prime habitat, much of it relatively high sweet gum/oak forest. Ivory-bills were also reported from other bottomland types, including cypress/tupelo swamp. This is a very different plant community. The now famous Luneau video is clearly in this type of area. It will be interesting to see how much the ivory-bills in the White River system utilize cypress/tupelo and other bottomland forest types. I could not help but notice that one of Luneau's photos, taken by one of his remote cameras, shows a water tupelo with abundant scaling near its base. The birds may require much more area of this habitat type than sweet gum/oak, but it may well be the more common habitat type in the White River NWR.

[GreatHornedOwl]

I could not help but notice that one of Luneau's photos, taken by one of his remote cameras, shows a water tupelo with abundant scaling near its base.

Couldn't that have been a beaver ?

Interesting post ! :t: So there in Arkansas the IBW may need larger areas ...

What also puzzles me also is that they don't mention any calls of the IBW ... the bird is very silent. I wonder why... perhaps those in the Singer Tract were noisy because they were territorial, and this Elvis is, on the contrary, just a wanderer who will move on soon when his food supplies are exhausted ?

There is clearly a different behaviour than in the Singer tract in 1939, I would find it interesting to read some theories about that here !

... Ah, but ain't the Ole Ivorybill just a spellbinding bird ! ;)

[krazyhorse]

[QUOTE]the limited gene pool may lead to interbreeding and problems related to that!but [QUOTE].... they are in Arkansas so what do you expect :) JUST KIDDING.. , does bring up some very interesting thoughts , iI cant help but think of the congaree in SC as a place were they could exist as well, eventually if found there maybe take some of the Arkansas birds move them east and vice versa with the SC bird thereby limiting the inbreeding to an extent, just an opinion and wishful thinking that they would be in SC

[fangsheath]

Well, here's the photo (bottom), you can judge for yourself. If you look closely there is a pileated woodpecker and a squirrel on the tree.

water tupelo scaling (http://www.ibwo.org/remote.html)

It's hard to get used to talking about ivory-bills in the present and future tenses. Of course, we don't know for certain that Elvis is still out there, but it's just awesome and amazing that we can even talk about the future of this bird in realistic terms now.

I think you are right on the mark, Elvis is a young bird who has dispersed from the core breeding area. He may disappear before long, but that should not cause us to despair.

As Remsen mentioned, the behavior of Elvis is clearly different from what Tanner saw. For years people have speculated that a few ivory-bills survived partly because they were the wariest of their kind. Now we have evidence suggesting that is the case. And it makes the case for the persistence of the birds elsewhere that much stronger. I am looking forward to hearing the acoustic evidence, it is coming soon. Our first listen at what are probably ivory-bill sounds in 60 years!

[GreatHornedOwl]

I think you are right on the mark, Elvis is a young bird who has dispersed from the core breeding area. He may disappear before long, but that should not cause us to despair.

As Remsen mentioned, the behavior of Elvis is clearly different from what Tanner saw. For years people have speculated that a few ivory-bills survived partly because they were the wariest of their kind. Now we have evidence suggesting that is the case. And it makes the case for the persistence of the birds elsewhere that much stronger. I am looking forward to hearing the acoustic evidence, it is coming soon. Our first listen at what are probably ivory-bill sounds in 60 years!

... I hope you are right ! And perhaps the core breeding area has been found already or will be found soon, but, for obvious reasons, is kept a secret ...

I see you live in Texas ? In your State the Ivorybill once lived in the "Pineywoods" (last 2 specimen collected 1904 in a place called Tarkington), these were/are more like upland Longleaf pine forests, if I'm correct, how is that habitat nowadays ? And the so called "Big Thicket" ? What do you think, any possibilities there for the future ?

[fangsheath]

That occurred to me too, I was a bit surprised that Fish and Wildlife was not actively discouraging birders from going to Cache River NWR, in fact they have maps suggesting viewing spots. I think it is possible that they have already found breeding pairs in White River NWR and are trying to direct people to this more peripheral area where Elvis was seen. But that is probably a little too conspiratorial. Even if they haven't found other birds, the strategy would make sense.

Upland habitats were not favored by ivory-bills, even in Texas. In the Big Thicket region, longleaf flatwoods and loblolly pine/hardwood forest interdigitated with bottomland hardwoods and evergreen shrub bogs. In this area, it stands to reason that ivory-bills would have utilized pine and mixed-pine hardwood forests on occasion. Today we have the Big Thicket National Preserve and various National Forest units, much of that is in fair but not great condition, although the longleaf forests are still generally very young by the standards of this plant community. Perhaps more significantly, there are still large continuous tracts of bottomland forest on the Neches and Sabine.

[GreatHornedOwl]

Upland habitats were not favored by ivory-bills, even in Texas.

Ivorybills in Cuba preferred upland habitats, so I've heard. And seriously, recent literature by Jerome Jackson and Philip Hoose suggests that they did live there in Texas too ... It may be even so that IBW was in origin NOT a species of river bottomland forests and swamps, but that it was forced in there after it's original habitat was logged over.


Perhaps more significantly, there are still large continuous tracts of bottomland forest on the Neches and Sabine.

Sabine river is a name that rings a bell re. Ivorybills ... but can't put the finger on it right now. Well, you never know ...

What you say about a young male bird wandering in a "peripheral" area ... it all makes sense you know . Well, there just have to be others, Elvis has to come from somewhere !

[Tim Allwood]

hiya

i think upland and lowland in Cuba

only viable habitat is now in Sierra Maestra - thought to persist there still but needs surveying

[GreatHornedOwl]

almost forgot - one of the searchers already has a book out about the discovery :

http://houghtonmifflinbooks.com/catalog/titledetail.cfm?titleNumber=689406

[fangsheath]

What is interesting is that almost every sizable river basin in the S.E. has had its reports of ivory-bills since 1950: the Neches, the Sabine, the Atchafalaya, the Pearl, the Apalachicola, the Santee, the list goes on. In many cases, the really rapacious logging happened prior to 1950, and the habitat has been slowly recovering since then. Having seen some of these areas myself, I can assure you that many patches of forest were missed by the commercial loggers, and large areas were never clear-cut. You gotta wonder.

[GreatHornedOwl]

Jackson ("In search of the Ivory-billed woodpecker", 2004, Smithsonian) mentions that the IBW was also found around 1880 in "large and dense pine forests in the northern part of Harris county and Montgomery county" in Texas. He then continues that IBW inhabits/inhabited both hardwood forests of the riverbottoms and pine forests of higher elevations, particularly old-growth [pine] forests supporting healthy populations of beetles. And : "they seemed to do best at the interface of these forest types, taking advantage of the resources of each."

[fangsheath]

That is an interesting piece of information. Near the interface between the longleaf pine forest and the coastal prairie region, and also on low terraces near larger river basins, there were large areas of mixed loblolly pine/hardwood forest. This area supported large loblolly pines but also large hardwoods, including southern magnolia, cherrybark oak, and red maple. In fact I grew up in an area that was originally this forest type, and I can readily envision ivory-bills utilizing it. They may also have invaded longleaf areas after hurricanes. Studies in Georgia have shown that after hurricanes, bark beetles, which normally do not proliferate in old-growth longleaf, temporarily gain a lot of ground because the trees have been severely stressed. I remember a conference in which forestry people were moaning and pulling their hair out because bark beetles were running rampant in the Big Thicket N.P. due to the Park Service's unwillingness to clearcut. It is hard to get people who have been trained in forestry to understand that dead trees are not necessarily bad.

[GreatHornedOwl]

They may also have invaded longleaf areas after hurricanes. Studies in Georgia have shown that after hurricanes, bark beetles, which normally do not proliferate in old-growth longleaf, temporarily gain a lot of ground because the trees have been severely stressed. I remember a conference in which forestry people were moaning and pulling their hair out because bark beetles were running rampant in the Big Thicket N.P. due to the Park Service's unwillingness to clearcut. It is hard to get people who have been trained in forestry to understand that dead trees are not necessarily bad.

Yes. Furthermore, asides from hurricanes, which happen frequently in the SE, there are forest fires : Jackson argues that the IBW may have depended also on large forest fires - beetles immediately invade freshly killed trees, and lots of sightings of IBW happened where there had been recent fires.

It's an interesting book, a good compilation of all that we knew of the IBW prior to april 28th 2005, and a good companion volume to Tanners study; Jackson is considered a world authority on woodpeckers I believe and researched the IBW since the 80ies - shall I look up the Amazon link for you and post it here ?

(I just wonder why Jerome Jackson wasn't involved in the searches in Arkansas ? He must feel sad now that he wasn't there ...)

[GreatHornedOwl]

... Hope it works...

http://www.amazon.com/exec/obidos/ASIN/1588341321/qid=1115505605/sr=2-1/ref=pd_bbs_b_2_1/104-6597087-2325566

[fangsheath]

Thanks, I've got the link now. I don't know why Dr. Jackson wasn't involved. He certainly has done his share to keep hope alive for this bird over the years.

[GreatHornedOwl]

Glad you got that link, it didn't really work when I checked it.

... Don't know why Jackson wasn't involved, but heard he may have had a difference of opinion with another prominent researcher (who is now in the forefront of this search) in 1999 about the Pearl sightings - when the double rap drumming turned out to be gunshots. Perhaps that is why, I don't know ...
I would have liked to see Jackson being involved in this one as well, he really did a lot for the Ivorybill, and in the 80ies -90ies he was the man who argued strongly that authorities shouldn't give up on the IBW ...

[Field Sparrow]

I imagine trapping/catching ivory-bills would be a complicated endeavor. With only 7 sightings and one, 3 second video of the Arkansas bird(s), during the last year, catching one would be a major feat. Can you just see a mist net large enough to hold an IBW? LOL
But, who knows, if enough birds are found, and inbreeding would be a problem, perhaps population exchanges could be an option. But if so, I see this many years down the road.

[GreatHornedOwl]

I imagine trapping/catching ivory-bills would be a complicated endeavor.

There is (in theory) a method that could work. It's more or less described in some of the existing literature.
Can't post that here however - hope you understand. ;)

[Rasmus Boegh]

There is (in theory) a method that could work. It's more or less described in some of the existing literature.
Can't post that here however - hope you understand. ;)

There's actually several ways this can be done (and as you say, not to be published here - the scientists and/or ringers that need it already know). Regardless, I'd certainly want some big gloves if I had to handle an Ivory-billed! I'm pretty certain that bill could do some damage. Anyway, as already said by others that's obviously not an option at this point where all we really know is that one individual apparently is present in a specific area sometimes. Indeed, I'd hesitate a guess and say they're likely focus on getting some basic knowledge about its behavior, saving the area where it (they, hopefully) are present and if possible try to provide corridors to neighbouring areas where habitat exists.

[jurek]

I'm not a biologist or scientist, but would like some thoughts based on the following scenario. Please humour me, I'm just trying to get a feel for the outlook for the Ivory-billed woodpecker.

Let's suppose there are 5 breeding pairs of IBWs in Arkansas, and maybe 5 to 10 pairs scattered elsewhere in Louisiana, Mississippi, and E. Texas, all states that adjoin Arkansas. Would this be enough of a start to slowly build the IBW
population up to a viable level, ASSUMING the birds are left alone and that suitable habitat slowly increases, or is the IBW inevitably doomed in this scenario because of the ramifications of "genetic impoverishment"?

I am a scientist and read about it a lot, even if I specialise in another branch of biology.

Surprisingly, no or almost no documented cases exist where species went extinct only because of low genetic variability caused by low population. Many species exist with low genetic diversity for man-made reasons or, surprisingly, natural reasons.

Examples are Black Robin from New Zealand (descended from 6 birds), Mauritius Kestrel (5 birds), lowland European Bison (7 animals). Naturally existing animals with low genetic variability include cheetahs, European beavers and, surprisingly, European badgers. Low genetic variability may be dangerous, but, just as well, species can survive it.

The biggest problem now is low population size. It means that few chance deaths or disturbances may finish off the species, few young can turn all of one sex, or even the birds may not be able to find each other.

[jurek]

That occurred to me too, I was a bit surprised that Fish and Wildlife was not actively discouraging birders from going to Cache River NWR, in fact they have maps suggesting viewing spots. I think it is possible that they have already found breeding pairs in White River NWR and are trying to direct people to this more peripheral area where Elvis was seen.

If they have 40 people and managed only 7 sightings, than probably they realised that they need more eyes to finally discover more birds.

If conspirancy is true, then check where FaW recently bought land and go there ;)

I think searching for markings on the bark and holes can be the a good strategy to find IBW. They stay on one place and are easy to document even by a layman. They can lead to IBW sighings later. But they are not foolproof - I read that presumed IBW feeding marks found in 1990's in Cuba turned to be hurricane damage.

[Rasmus Boegh]

Black Robin from New Zealand (descended from 6 birds).

... as mentioned in a previous post the Black Robin actually are descendants of a single pair (and the total population was 5) and no-one has been able to explain why they seem to have normal survivability despite a near complete lack of minisatellites (see the attachment - from Ardern and Lambert 1997. Left is the Black Robin, right is the closely related Bush Robin, which has experiances a bottleneck recently, but still exhibit a far greater variation than the Black Robin). On the other hand there are several examples where a small gene pole is believed to be the reason for a serious decline, although the vast majority are from captive populations, where especially survivability for offspring has been relatively easy to measure and document from generation to generation. So, no doubt that it often (probably even usually) pose a serious problem, as documented in several tests (e.g. Jimenez et al. 1994) and described in various theories (i.e. partial dominance hypothesis and the overdominance hypothesis). However, there are also several well documented examples (Jurek mentioned some of them) where surprisingly small populations seem to manage just fine and there indeed are genetic theories that describe how populations with a high level of homozygous alleles can be good for a population, as recessive deleterious alleles are removed. For a more thorough look at inbreeding and the effects see Waller and Keller 2002. Note that several have mentioned the Cheetah in this thread, but it is mistaken to believe that they have experiances no effects of their low genetic diversity. Indeed, it is well known that they have an unusual high level of sperm anomalities (Caro 2000). So, there clearly are many things that are poorly understood in this matter, but it is clear that in most (but not all!) cases, high genetic diversity is better than low genetic diversity in terms of survivability.

[Tim Allwood]

Cheers Rasmus

i mentioned the cheetah sperm aberancy several post back

i guess high levels of homozygosity are good in favourable conditions but very problematical if for some reason or other conditions change...

although the Black Robins are doing well, their genetic similarity could still make them susceptible to some ill fortune one way or another that a genetically divergent population might stand more chance withstanding

and as you say, surely the overall point is that high genetic diversity is preferable over low

[fangsheath]

I agree, it is much easier to find ivory-bill sign than the birds themselves. However, scaling that looks promising has in the past sometimes turned out to be the work of pileateds. I strongly suspect that it will be possible to get some microstructure, and perhaps even macro, diagnostics to distinguish the two reliably. It is something I mentioned to Luneau and Fitzpatrick a few years ago, and they are working on it. It is critically important to gain such abilities so that we can, in a reasonable time, find out if and where there are other populations out there.

[jurek]

... as mentioned in a previous post the Black Robin actually are descendants of a single pair (and the total population was 5)

Woops my fault.

[maersk]

if a few males and females are found the logical thing to do would be recapture them like they did cali condors and start a captive breeding program

[jurek]

If anybody is really interested, than there are two reviews - but need to go to a good library:
Amos W, Balmford A. When does conservation genetics matter? Heredity. 2001:257-65 and:
Frankham R. Genetics and conservation biology. C R Biol. 2003 S1:S22-9.

Inbreeding is or can be harmful, but it does not mean certain or even highly probable extinction of a species.

I talked to some people interested or involved in conservation and they usually overestimate the role of "inbreeding". There are lots of misconceptions. For example, cheetahs are inbred. But so low genetic variability of cheetahs could only happened if population was very low for centuries or millenia.

For ivory-billed woodpeckers: if they lived for several generations in a small population, there are chances that harmful mutations were already "purged" from their population. The best way to ensure that their genetics will not make any harm is to let the numbers to build up quickly.

[fangsheath]

Well I certainly hope that can be avoided. I would like to think that level heads at the CLO, the Nature Conservancy, Fish and Wildlife, and other conservation organizations would prevail, knowing that ivory-bills have been co-existing with hunters in the White/Cache system for years. If we are going to save this bird, we will need the cooperation of everyone who gives a rat's anus about it, including hunters, fishermen, birders, and yes, farmers and cattle ranchers, among others. The last thing we need is to alienate the bird's neighbors. I hope hunters particularly will make their voices heard with U.S. Fish and Wildlife.

[pemburung]

Just a general observation, as I rather like field observations vs theory. A good case against overly worrying about genetic problems in low populations (not that it is not real, I'm talking about over-worrying here) is pretty much every relatively remote non-continental island with endemics that you've ever visited. It's not likely that a founder population of 500 - or even 50 - populated many of these, just one or two, or even a pregnant/gravid female. To say nothing of the number of islands with purely female populations of geckos, and the many other parthenogenic lizards. I say this as I have seen examples of - this is absolutely true - zoo animals not being allowed to breed due to possible genetic inbreeding, when they were virtually the only animals breeding at all! It seemed it was thought that no animals at all was better than some possibly inbred animals.

And as someone said earlier, these are southern birds. It's practically a duty.

[fangsheath]

I think you have a valid point, although one wonders how many founding events were followed by extinction before one finally took hold and persisted in many of these cases. There is also the fact that in many cases there is (rare) influx of new genes. And I do think the loss of the range of genetic diversity within any species is a tragedy. But, as I have indicated, that is not necessarily irretrievable in this case. What is important is that we have every reason to believe there are still living population(s) of this species out there, and those of us whose dreams it has haunted for many years have learned our lesson. We will not give up on it again. We will fight for this survival of this bird.

[lazybirdwatcher]

I've been watching (reading) with intense interest a while now, these message threads concerning the IBW.

To someone like me, all this extinction stuff can seem farfetched sometimes. I was just reading about the passenger pigeon. I didn't know there were billions of them in 19th century America. If such a thing can happen why does't it happen to other birds like robins, for example? Obviously, the dodo had much less a chance for survival being on an island. I can reason that out. But a bird that is so numerous? I don't know...

It's strange how these things occur. I was looking up info about the Great Auk, also hunted to extinction, among other kinds of animals that seem to have dwindled away to nothing. One being the Tasmanian Tiger, which I saw a television show not very long ago telling how one was suspected of exisiting in captivity or something. Old film of it and all.

Then there's things like that prehistoric fish caught off the coast of Africa. Coelacanth, I believe. Now considered not extinct.

Fascinating either way you look at it.

Bob