It is unfortunate that I just do not have the time to do any 'proper' blog writing at the moment. Winge winge winge. So I'm going to do a bad thing, but something that I've been advised to do, and something that lots of other people do anyway: I'm going to start re-publishing old Tet Zoo articles from ver 1. We'll call this 'From the archives'. If you're a long-time reader then, sorry, you're going to be seeing old stuff that you've seen before. But if you're a new "I've only known about Tet Zoo since it's been on ScienceBlogs" reader, well - ta da! The article here is the very first full-length blog post I ever published and appeared on January 24th 2006. It's out of date in places but, I figured, what the hell. The original version is here.
Welcome to the first of my blog essays - and it's not as if I planned to write this, it's just that the idea came to me while I was eating biscuits. One of my favourite 'fringe' subjects within tetrapod zoology concerns the alleged ability of eagles to attack and kill unusually large mammals, including people. Most people, and indeed most ornithologists and other zoologists, don't take this notion too seriously, or indeed dismiss it immediately as utter nonsense. Fortean literature is replete with stories of eagles (usually European Golden eagles Aquila chrysaetos) attacking, killing and/or carrying off people, typically (but not always) young children, with the best known story of this sort being that of 5-yr-old Marie Delex from the French Alps. It's pretty inconceivable that even the biggest eagle could carry off a human child, but as for whether they could kill one, well, read on.
Two recent items in the media have concerned this issue, and both caught my attention.
Firstly, we have news from researchers at Ohio State University on the death of the Taung child (or Taung baby, depending on your preference). This is the famous juvenile australopithecine specimen described by Dart in 1925, and thought to have been a 3 or 4 yr old. Following up on Brain's observations of 1981 that the Taung assemblage represented an accumulation produced by a large carnivore, probably a leopard, Lee R. Berger and Ronald J. Clarke (1995) showed in Journal of Human Evolution that a large eagle was the most likely killer of the juvenile. The case was good: the assemblage consists of smallish mammals (like mole rats, spring hares and small antelopes), evidence for carnivorous mammals is absent, nick marks corresponding to those produced by eagle beaks and talons are present on some of the bones, and eggshell was also discovered at the site. The new discovery is that nick marks around the orbital margins of the Taung child demonstrate once and for all that an eagle really was the killer. Great stuff - I look forward to the paper [update: it has since been published (Berger & McGraw 2007)] [in adjacent picture, Lee Berger holds the Taung child's skull. A stuffed eagle looks on].
What's a little odd is that several people have started asking questions about the lifting abilities of the Taung eagle relative to the weight of the juvenile australopithecine (oh, and by the way, the eagle is [I understand] presently a theoretical one - the evidence for its presence is there, but the eagle itself has yet to be found. It has been considered by some workers that the African crowned eagle Stephanoaetus coronatus [shown below, from wikipedia] was the most likely culprit - more on that at another time). This is odd because it was discussed to death the last time there was a flurry of interest in the 'eagle as killer' theory. Anders Hedenström (1995) showed in Nature that, given that Stephanoaetus can carry animals weighing just over 6 kg (wow!), then it would have to have dismembered the australopithecine. Which is fine, given that the specimen is only known from its skull. However, Hedenström argued this based on an assumed mass for the Taung child of c. 10 kg, and that might have been too high.
Berger & Clarke (1996) - in an article published on the same page as Dave Martill et al.'s brief note on the possibility of finding medullary bone in non-avian theropods [more on that in another post] - countered that evisceration of the juvenile prior to its carrying was likely, given that large extant raptors commonly do this. This could mean a 30% loss in body weight of the juvenile, thus bringing it close to or within the short-range carrying abilities of Stephanoaetus. It's also worthy of note that Berger and Clarke brought attention to cases where big living African eagles simply must have lifted animals that weighed more than 6 kg, so this perhaps wasn't the 'upper' lifting limit that Hedenström thought it was.
So, to those people who have suggested that the Taung eagle killed the australopithecine there on the spot (oh, I see, coincidentally in the middle of a veritable midden pile of eagle-killed small mammals), I say check out the literature on eagle lifting abilities.
Speaking of killing the australopithecine on the spot, this introduces the next thing I wanted to talk about... can a big eagle kill a mammal that's too big for the eagle to carry? Like it or not - and I've received some vitriolic emails for promoting this idea (Naish 1998, 1999) - the answer is a definite yes. In fact the ability of large eagles, specifically Golden eagles, to kill relatively enormous prey is not doubted and well established. Between 1987 and 1989 representatives of Animal Damage Control (ADC) were called in to check out mysterious domestic cattle deaths that were occurring in Socorro County, New Mexico. 6 calves were killed and 13 injured, with the biggest calf attacked weighing 115 kg. The attacks were caused, unquestionably, by a pair of local Golden eagles, as verified by observed attacks and by the talon marks on calf skulls. The problem stopped when the eagles were removed (and 'removed' probably means 'shot' I guess [update added Sept' 2008: no it doesn't. Steve Bodio pers. comm.). It seems the eagles killed by puncturing the skull base. I know this all sounds pretty incredible, ridiculous even: if you don't believe me see Robert Phillips et al.'s 1996 paper in Wildlife Society Bulletin. You might be as surprised as I was to learn that Golden eagles are also documented as killers of Mule deer, Pronghorn and semi-domestic reindeer, and again this is all documented in the technical literature and I'm not making it up. For killing of juvenile deer, see Cooper (1969) for Red deer and Ratcliffe & Rowe (1979) for Roe deer.
What was the second thing in the media that I wanted to mention? On Jan' 17th (2006), the BBC broadcast 'Bill Oddie's How to Watch Wildlife' (or whatever), and it included something I've never seen before on film. Oddie and a colleague were observing a wild Golden eagle in the Cairngorms, and the camera was on the bird too. Suddendly, it swooped down low on an adult Red deer. The deer ran down the hillside, pursued closely by the eagle, which swerved and jinked to follow and harass it. The eagle wasn't about to dig its talons into the deer - it looked as if it was trying to see if it could get it to take a nasty fall down the hill. This behaviour has been mentioned for some other raptors - Lammergeiers Gypaetus barbatus are said to do it to ibex and chamois - but I didn't know Golden eagles did it. On Lammergeiers [one shown here, from wikipedia], Berridge (1934) wrote 'A favourite method of dealing with [ibex and chamois] is to swoop down suddenly upon a prospective victim that may be poised somewhat insecurely upon the steep hillside, so that the startled beast loses its foot-hold, and goes tumbling to death in the ravine below' (p. 219). The scoop is that Lammergeiers don't just try this out on ibex and chamois, they will also try this on humans too, and I know this because it has been reliably reported by a professional biologist (I don't have his permission to cite it as a pers. comm., but will try and get this on record).
One final thought on this subject, though to be honest it's not that original and many people end their articles on nasty eagles with the same thought. The raptors I've been discussing here aren't particularly big: Golden eagles max out at 6.6 kg, and Stephanoaetus is less than that. Given that there were, recently, extinct eagles that were substantially bigger than this - Haast's eagle from New Zealand weighed about 13 kg (in females) for example - then eagles as a group simply must have been capable of even more amazing feats of predation.
Finally, here's the Christmas card I sent people in 2004...
Refs - -
Berger, L. R. & Clarke, R. J. 1995. Eagle involvement in accumulation of the Taung child fauna. Journal of Human Evolution 29, 275-299.
- . & Clarke, R. J. 1996. The load of the Taung child. Nature 379, 778-779.
- . & McGraw, W. S. 2007. Further evidence for eagle predation of, and feeding damage on, the Taung child. South African Journal of Science 103, 496-498.
Berridge, W. S. 1934. All About Birds. George G. Harrap, London.
Cooper, A. B. 1969. Golden eagle killed Red deer calf. Journal of Zoology 158, 215-216.
Hedenström, A. 1995. Lifting the Taung child. Nature 378, 670.
Naish, D. 1998. Big bad eagles 2: sheep and cow on the Golden eagle menu. Mainly About Animals 36, 10-12.
- . 1999. Big bad killer eagles. Fortean Times 122, 48.
Phillips, R. L., Cummings, J. L., Notah, G. & Mullis, C. 1996. Golden eagle predation on domestic calves. Wildlife Society Bulletin 24, 468-470.
Ratcliffe, P. R. & Rowe, J. J. 1979. A Golden eagle (Aquila chrysaetos) kills an infant Roe deer (Capreolus capreolus). Journal of Zoology 189, 532-535.
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On the subject of bad dinosaur names, Stephanoaetus coronatus appears to mean "crowned crowned eagle".
Yes, that's because it was originally Falco coronatus Linnaeus, 1766. By the late 1800s it was being included in Spizaetus and not until 1922 did W. L. Sclater decide that it needed its own genus.
Bearded vultures attacking man is, I think, referenced in HBW.
BTW, Mongols trained golden eagles to attack humans. I doubt this was very effective weapon and eagle lived long, but still...
A few years back I watched a video on line of an eagle (in Mongolia I think) take down a small deer. It's impressive that hazards predators assume when at work, eagle no less than lion. The eagle knocked down the deer. With talons dug in, predator and prey summersaulted together at least once, the eagle had to struggle to end up on top. It gave me a whole new take birds. It looked quite like a lion rolling a buffalo.
Bill, you might be referring to the video I posted here (though I'm not saying of course that Tet Zoo is the only place on the web where you might see it: I learnt about it from Querencia).
On the subject of bad dinosaur names, Scrotum humanum not only appears to mean "human scrotum", it *does* mean "human scrotum". :-)
But note that 'Scrotum humanum' was *never* used as a name, only as a label on a plate: this was by Richard Brookes in 1764. Some authors (notably Halstead & Sarjeant 1993) have written of 'Scrotum humanum' as if Brookes intended it to be used as a binomial, but there's no indication of this - all he did was illustrate the specimen and put the label 'Scrotum humanum' next to it. This was realised by P. K. Tubbs of the ICZN who responded to Halstead & Sarjeant's ICZN petition to 'suppress the generic name Scrotum' and basically said that they were mistaken for the reasons I've given above. I don't know about Sarjeant, but I never thought that Halstead took this claim seriously anyway.
Ref - -
Halstead, L. B. & Sarjeant, W. A. S. 1993. Scrotum humanum Brookes - the earliest name for a dinosaur? Modern Geology 18, 221-224.
Coming to English names, Lammergeier (lamb vulture) was renamed Bearded Vulture/Bartgeier for PR reasons.
And insignificant but endangered rodent from Philippines named Panay Cloud Rat (I think it lives in cloud forest on island Panay) was renamed into somewhat poetic Panay Cloudrunner.
Good to see this back again wit some nice new pix.
"Mongols"-- actually Kazakhs in Mongolia and elsewhere--- still hunt foxes, wolves, and various hoofed things with eagles-- I have been there, and written a book about it (Eagle Dreams.)
In the Czech Republic there is a falconry festival every year where golden eagles are flown at roe deer in large fields where they graze. They take them as easily as a goshawk does a hare. There are various versions on YouTube.
Meinertzhagen claimed that a lammergeier stooped sat him while he was traversing a mountain ridge. Of course there are those who will tell you that he was not the most truthful man alive...
Yes, Haast's Eagle routinely killed moa 100 kg or larger (up to 200 kg Dinornis). So it would have been preadapted to hunt humans when they arrived here in New Zealand. No wonder they went extinct so fast.
Haast's Eagle had some vulturine skull adaptations (elongated beak, nostrils partially occluded with bony scrolls, etc) presumably because it had to plunge its head right into the bowels of its prey. Do any of the other predatory eagles mentioned above have some of the same adaptations, or are large animals not a common enough prey item for such things to evolve?
Mike: so far as we know, Haast's eagle was unique as goes its vulturine and terrestrial adaptations. As you know, it's probably not coincidental that it evolved in a land devoid of large terrestrial predators. In other words, 'We know from well documented taphonomic evidence that Haast's eagle could and did kill even the very biggest of the contemporary moa, and unlike big eagles in continental environments it could probably get away with gorging itself at a carcass without having to worry about flying off in a hurry'. That's from here.
Haast's eagle was also covered on Tet Zoo ver 1 here.
Based on Haast's eagle, we might speculate that established terrestrial predators (namely carnivorous mammals, both placentals and marsupials) have prevented eagles from becoming strongly terrestrial in continental environments.
"note that 'Scrotum humanum' was *never* used as a name"
Sure. But even so - did his buddies dare him to do this after one too many bottles of port, or what? :-)
(Second favorite [real] goofy dino name: Irritator.)
(Whoa, special trivia bonus! -- it's Irritator challengeri, after *the* Professor Challenger. Style points to Martill, Cruikshank, Frey, Small and Clarke.)
I'm surprised the Haast's eagles didn't *win*. How many were there? Surely there were more of them than humans at first...
I hoped that's why it was challengeri. I liked that book.
Darren-- I periodically reread your old posts ANYWAY, but this was well worthwhile: new pictures, new comments, and new old Christmas card! Nice post.
Hmm. If some people have thought that "Scrotum humanum" was close enough to being a Linnean binomial to be worth petitioning the ICZN about, are there people who think that a full systematic story about gian salamanders has to mention a supposed "Homo diluvii" (subspecies: testis)?
Homo diluvii testis is not a subspecies name, diluvii testis is a descriptive phrase published as a unit. Taxon names were generally polynomial before the introduction of binomial nomenclature, and as Homo diluvii testis dates to 1732 it pre-dates the official beginning of valid zoological nomenclature in 1758.
(The only pre-1758 publication accepted by the ICZN is Clerck's Aranei Svecici of 1757, which would officially make Araneus the first genus ever published.)
I'm surprised the Haast's eagles didn't *win*. How many were there? Surely there were more of them than humans at first...
Compare dates of the definitive colonization of New Zealand with the rest of the Polynesian Pacific.
Who's to say that they didn't win at first?
First of all, thanks for re-posting these old articles, Darren! Will you re-post them all, or just a select few?
I am slightly hesitant to point this out, as it usually turns out that you already know anything tetrapod-related. But are you aware that there is, besides eagles, another documented cattle-killing bird species? That species is the American black vulture (Coragyps atratus).
Black vultures mostly eat carrion but they have been recorded to harass and kill fairly large animals in feeding frenzy-styled mob attacks. McIlhenny (1939) described, in quite chilling detail, such attacks on skunks and opossums; the unfortunate victims were literally torn apart by the vultures. (Incidentally, the skunks' chemical defences seem to be wholly inefficient to deter such attacks.)
In some parts of the US, black vultures are also a serious problem for livestock breeders, as they kill newborn piglets, lambs and even calves (Lowney, 1999; Avery & Cummings, 2004). These attacks typically occur when the vultures spot an animal out on pasture that's about to give birth. Usually the vultures settle for the afterbirth, but if the mother is too exhausted or inexperienced to defend her offspring, the vultures will attack it (by first pecking out its eyes). Sometimes the vultures even attempt to attack the adult cow in the same way.
In fact, perhaps Coragyps is the closest living analogy we have to Velociraptor...
Avery, M.L. & Cummings, J.L. 2004. Livestock depredations by black vultures and golden eagles. Sheep & Goat Research Journal 19, 58-63.
McIlhenny, E.A. 1939. Feeding habits of the black vulture. The Auk 56, 472-474.
Lowney, M.S. 1999. Damage by black and turkey vultures in Virginia, 1990-1996. Wildlife Society Bulletin 27, 715-719.
So basically this boils down to a question of the load-carrying capacity of African and European eagles. Are there any predatory swallows involved?
As for Haast's Eagle driving humans out of NZ, their range never covered both islands, so far as I know, and so it was probably possible for the Maori to establish a foothold before going eagle hunting.
Even so, there are some myths of young Maori being kidnapped and terrorized by bird-women...
Last year several crows (or ravens, this was not that sure) attacked and killed seven lambs in Austria. Just imagine what raptors could do when they would hunt in bigger packs.
I read that a group of Griffon Vultures killed a cow in Spain in mass attack, when cow laid down. It happened when BSE scare led people to remove cattle carcasses and vultures were starving. But it was just newspaper news.
No. He honestly believed the thing was a petrified human scrotum. Keep in mind that paleontology didn't exist yet; Linnaeus classified all fossils in the mineral kingdom, not the animal and plant kingdoms.
Perhaps the reason why no bird of prey hunts big animals in groups is competition from larger predators. Group of 10 eagles might kill a deer, but would not defend it from a lion.
Off topic, but fitting the blog: Nile crocodile in a gallop:
(bernstein > Round the World Trip > Malawi > Liwonde , pic 38 of 59)
Linnaeus classified all fossils in the mineral kingdom, not the animal and plant kingdoms.
But he was right; Fossils are minerals, and not animals or plants, thats what fossilisation means, after all.
Fastinating guy; but what was it with the Shaman costume??
OT: Solar powered flight? (hope no errors)
cold blooded: tiktaalik, amphibians
cool blooded: archosaurs, reptiles
warm blooded: dinosaurs, pterosaurs
hot blooded: birds, mammals
cold blooded = water/mud adapted (+ naked mole rat)
hot blooded = land/air adapted
Since bats fly at night, they must be hot blooded, but may have originated as diurnal canopy gliders (w/o owls)?
Did the wide spanned pterodactyles use their wings to absorb solar energy to warm their blood for powered gliding/flight? Could that have been the origin of wings among those perching on sunny tree/cliff tops? The addition
of downy feathers in birds indicate no more need for sunlight, so increased homeothermy? Then flight feathers developed? Canopy animals unlike ground and water animals are already light boned and sun warmed, if they consume sugary saps, flower nectar, sweet fruit, flying insects then homeothermy is a good option, adding skin flaps on the forelimbs would allow speedy tree to tree transit.
If you mean zoological speculation, ratio of surface to volume and efficency of photosynthesis conspired together, and say that active sunlight-powered animals bigger than few millimeters are impossible.
I don't think DDEden is talking about photosynthesis; i think ze's talking about solar-thermal energy, as used by living squamates in areas with cold nights. Ever seen an adder or a sand lizard "sunning itself"?
Converting solar energy into any other kind of energy through any kind of chemical process is vastly inefficient, which is why photovoltaic electricity isn't really viable outside the tropics. But using it directly to heat water (or blood) is very easy and very efficient.
I think the speculation is that, assuming pterosaurs were not fully homeothermic, they would have needed to increase their body temperature to be active enough for powered flight, and thus the very large skin area of their wing membranes could have played a role in heating them more efficiently (which would make the best reconstruction be with the membranes being dark coloured).
There are probably reasons why this is unlikely, but i don't think it's as out there as suggesting that pterosaurs could photosynthesize...
DDeden, I don't know where to begin. You should first learn something about these several topics before talking about them.
For starters, there is no difference between "warm-blooded" and "hot-blooded".
Also wrong -- it's always cooler in forests than outside (except sometimes when it's below freezing and there's wind chilling).
I don't see why. Also, flower nectar and fruits did not exist before near the end of the Early Cretaceous.
Leading to gliding -- but whether flapping can evolve from gliding is controversial.
is not done by animals except those with photosynthetic endosymbionts (like shallow-water corals). Heat from the sun can raise the body temperature so that the metabolism can work at its maximum speed, but it can't increase that maximum speed, which is usually much higher in warm-blooded than in cold-blooded animals. If you give a lizard heat but no food for long enough, it won't run around but starve.
There is no reason for such an assumption.
" Converting solar energy into any other kind of energy through any kind of chemical process
is not done by animals"
I am aware of this, just didn't think it necessary to point out. Possibly i was guilty of trying too hard to find something approaching plausibility...
Is there evidence that pterosaurs *were* fully homeothermic?
(I'm getting increasingly fascinated by pterosaurs, and just how "out there" they were. Animals like Tapejara, Nyctosaurus and Hatzegopteryx just seem like they couldn't possibly have been imagined even by the wildest-imaginationed fiction writer. I can't even begin to imagine what they would have looked like in flight, it's kind of mind-boggling that they were even capable of flying... there's probably very little i wouldn't believe about them considering how unbelievable what's known to be true already is...)
On eagles, has Darren covered Washington's (aka Audubon's eagle)? A cryptid, inland-living Haliaeetus with a >3m wingspan, drawn and painted by a world-renowned ornithologist and illustrator with detail to convincingly place it in a known genus but no known species, from specimens he handled himself...
When hunting a wolf, the golden eagle overtakes and swoops down on the fleeting animal, gripping the mask with one foot, in order to prevent the wolf biting, and the back with the other. The great bird then does its best to bring its two feet closer together and thus break the animal's spine, but with a wolf this is seldom possible, and the eagle is content to hold it until the arrival of its master. It is said that if an eagle several times misses its stoop it becomes so angry that it will sometimes fly at a man. On one occasion an eagle swooped at its master because he was wearing a cap of fox fur. The eagle's talons pierced an artery and the man died.
- Seton Gordon, "The Golden Eagle: King of Birds"
Well, the smaller ones probably couldn't have flown otherwise. Then there's the fur, and then there's the pneumatic skeleton that very strongly suggests a bird-style respiration system (even bats don't have air-filled bones).
There was a nature series in Spain decades ago which prominently featured an eagle carrying off a wild goat in the opening credits. This was really the series which started the genre of wildlife documentaries on Spanish television, I suspect. Unfortunately, Felix Rodriguez de la Fuente was less than kosher with the ways he obtained his footage at times. In this case, I believe that the goat had been maimed to obtain the footage and the eagle filmed was a trained eagle (Dr. Felix Rodriguez de la Fuente was a master falconer).
Here's a video clip which shows the event from which that opening sequence was drawn:
African or European?
This is some footage of a spanish wildlife series by Rodriguez de la Fuente. He was quite a figure here in Spain, don´t know how much outside impact he had... Anyway, you can see some bastard eagles throwing goats off some cliffs.
Wonderful blog, I´m becoming quite a fan...
Thanks for comments. Féliz Rodríguez de la Fuente's footage of Golden eagles killing goat kids by pulling them off a cliff was covered previously on Tet Zoo here. While I described the footage as 'faked', the footage showing the killing was most certainly not faked (though it was staged).
If you mean some winged animal using wings to warm itself - its a bit tricky. In flight, air passing the wing cools the animal faster than it warmed itself before.
It would be possible with animal which flies very rarely (like gliding lizard Draco volans).
I've done a fair amount of solo mountaineering in Alaskan golden eagle territory and I pay attention to mountaineering literature, and I've never heard of eagles attempting to scare climbers into falling.
Not saying it's never happened, but it would have to be extremely rare. I wonder if what might look like that behavior may actually be defense of an unobserved nest, fledgling, or kill site.
But, I also know of a building maintenance man in California who had to armor himself with with a garbage can lid and a broom, and do battle with a peregrine falcon pair when he had to get up on his building's roof.
Brian: the 'attempting to scare climbers into falling' stuff concerned lammergeiers, not golden eagles.
"African or European? " - I don't know that - aaaarrrrgggggg :)
Started off as a nice sensible post about raptors picking on dogs/cows/random mammals and now it's just got silly.
I had nothing useful to contribute to this interesting thread, so rather than have the sense to say nothing I latched on to the Monty Python subtheme.
OT: Cold blooded critters (fish, N mole rat) don't sun themselves, can't handle strong sunlight. Cool/warm blooded critters (crocs, snakes, black vultures) do. Large fliers are dark, except seasonal migrants (cranes). Early gliding birds & pterosaurs on cliffs and canopy were sun-warmed, helped their lift/glide, their dark wings didn't sweat and lacked fur/feathers. As homeothermy improved with high energy diet, less need for sunlight, more need to retain internal warmth, so down developed on torso, then to wings, then flight feathers and smaller-lighter tails/wings.
Flapping wings was for cooling/aeration, just like insect wings, which developed into partial flight. Both coral and sloths have symbiont algae which photosynthesize, but that wasn't my point. Top of canopy was safe for early birds/pterosaurs, except for strong wind; thin twigs couldn't support big snakes or reptiles (which tend to attack eggs), so skeletal lightness and tail reduction (replaced with long feathers) was selected for.
There was a nature series in Spain decades ago which prominently featured an eagle carrying off a wild goat in the opening credits. ... While I described the footage as 'faked', the footage showing the killing was most certainly not faked (though it was staged).
Nooo-one expects a Spanish eagle fiction!
When attacking unusually large prey, I imagine that golden eagles rely as much on the "psychological" aspects of shock and terror in order to overcome their quarry, as much as their physical strength. Especially when trying to startle prey into losing their mountainside footing, as mentioned above.
In other words, their chief weapon is surprise.
Surprise and fear.
Their two main weapons are surprise. And fear. And ... I'll come in again.
"'attempting to scare climbers into falling' stuff concerned lammergeiers,..."
OK. I don't really follow European mountaineering literature, so maybe they've reported the behavior. If they haven't, that again suggests it has to be extremely rare or a misinterpretation of their behavior.
But not because they're cold-blooded! Naked mole rats would get sunburnt -- and they aren't cold-blooded, they are intermediate! --, and fish can't risk drying out.
You invent terms and categories for no reason. Crocs and snakes are cold-blooded (ectothermic, poikilothermic, bradymetabolic and bradyaerobic), all birds are warm-blooded (endothermic, homeothermic, tachymetabolic and tachyaerobic).
And swans, and most albatrosses...
Pterosaurs perhaps, but birds did not go through a phase where they were strongly adapted to climbing, and there's no evidence for a gliding phase in bird origins either.
No. Dinosaurs in general were warm-blooded. That logically includes the ancestors of birds!
Bird wings consist only of feathers. Without feathers, a bird arm is not a wing.
This speculation is unnecessary for birds, because their ancestors were already homeothermic.
Are you completely unaware of Sinosauropteryx???
Why would they need that much cooling -- and how does that work in animals that don't sweat?
Besides, insect wings are derived from tracheal gills that were most likely used as fins for swimming and then for moving forward while standing on top of the water -- something that stoneflies still do.
The symbionts of corals are intracellular and actually feed the coral. The symbionts of sloths live in their hair and do nothing for the sloth except making it green (camouflage)!!!
Early birds were not on top of any canopy.
Snakes have only existed for the last 100 or so million years, and terrestrial snakes for even less. We have no idea where any pterosaur nested; given the poor climbing and flight abilities of animals like Archaeopteryx, it's doubtful that they nested in trees either.
Then why did the latter take the pterosaurs so long, while the former is common to all saurischians?
You should get out less and read more. You have a lot to learn.
The origin of wings in insects is looking a lot more iffy in recent years than it was not so long ago, and the paranotal ghost has begun to rear its head. The idea that surface-skimming could have given rise to flight has taken a pretty significant hit with the increasing establishment that stoneflies are not a particularly basal lineage within insects, and those stoneflies that exhibit surface-skimming are not necessarily basal within stoneflies. This is not to say that surface-skimming was automatically not a stage in the evolution of flight, but even if it was, surface-skimming in modern taxa is a more derived feature rather than being retained from the pre-flight ancestor.
Of the four basalmost major pterygote lineages, living Ephemeroptera and Odonatoptera have aquatic nymphs while basal Neoptera and Palaeodictyopteroidea probably had terrestrial nymphs. The most widely supported phylogeny for insects unites Odonatoptera and Neoptera to the exclusion of Ephemeroptera. It's an open question at present whether the aquatic nymphs of Ephemeroptera and Odonatoptera represent a shared plesiomorphy of the pterygote ancestor or an independent derivation in the separate lineages. The exceedingly poor fossil record of super-basal pterygotes may suggest a terrestrial rather than aquatic ancestry for the group, but as an argument from negative evidence it's pretty weak.
It has been shown developmentally that the genes active in wing development are also those involved in crustacean gill development. However, there are enough examples of gene processes being convergently co-opted in separate lineages (for instance, the same genes are involved in arthropod and chordate limb patterning despite the common ancestor of these groups almost certainly not having limbs) that this does not completely seal the deal.
OT: What's the chance that some type of (basal) coastal pterosaurs evolved eventually into birds? Zero?
I'm thinking that theropods and Aves developed from a basal flighted pterosaur with primitive feather-scales which became islanded (with no ground predators) and (as typical) reduced flight, some becoming flightless partly-ratite-like (Theropods) while others maintained gliding, then some re-evolving flight (early Aves) due to new niche opportunities. All of these could have had a variety of scale-feather combinations. Some could have nested in canopy, others on sea cliffs, others in tree hollows, others on soil, or sandy beaches. (Thinking of New Zealand and Papua bird variety.)
> I'm thinking that theropods and Aves
> developed from a basal flighted pterosaur
> with primitive feather-scales
That's a just-so story. Reminds me of Sera's idea that elephants, sirenians and desmostylians were late surviving dicynodonts - all other mammals are, of course, amphisbaenids :-).
DDeden:it is fun to speculate, but you do not seem to understand how science works. We do not come up with an idea and then look for evidence - instead we look at evidence and then propose an idea (an hypothesis) that might explain it. There is much data on the early history of pterosaurs and birds, you must look in detail at this BEFORE speculating on scenarios about their evolution.And none of the evidences lean towards your suggestions by the way.
Would an eagle always need to lift an object it was carrying into the sky? Aircraft flying very close to the ground get extra lift from an sort of air cushion; how directly this applies to a flapping wing I don't know, but an eagle might move a heavy body some distance by ground skimming.
OT: Note the pattern, then the conjecture:
1) Running biped short-forelimbed short-tailed Ostriches derived from flying long-forelimbed short-tailed ancestors.
2) Running biped short-forelimbed long-tailed Theropods derived from flying/gliding long-forelimbed long-tailed ancestors.
A flying predator attacking hornless prey from above, would eventually select for prey with horns, which would then select for ground dwelling predators which attack horned prey from below to attack the soft parts (throat). Theropods share traits with birds because they derive from flying/gliding/climbing predatorial ancestors, not sauropod-like ancestors, I'd think. It's not so much an idea, as it is pattern recognition.
Chris Clark -- Interesting idea; you are referring to what's called "ground effect" or "in ground effect" -- there is a bit about it here: http://www.wigetworks.com/ww_tech.htm
Googling +birds +"in ground effect" turned up some statements that some baby birds use this effect when learning to fly, and an article (not available to me) speculating that Archaeopteryx was a habitual "in ground effect" flier. So birds can use this effect, but it limits them to about half a wingspan above the ground. Flying long distances this way is also easier if the surface beneath is relatively flat and smooth; the effect will be lost whenever the distance between the bird and the surface gets too big. So it's easier to use above water or a very flat land surface; not so practical for hilly terrain.
Seton Gordon's description of wolf eagles is derived from 19th century traveler's tales like Atkinson's and is a bit overdone. The eagles I saw in Mongolia (and the ones in eastern Europe who routinely kill roe deer) are almost placid with their handlers and wouldn't "turn on" them. I doubt they have to break wolves' necks-- the tissue damage and blood loss from their strike is astonishing. They do try to control the muzzles of wolves and foxes.
All Kazakh eaglers wear fox- skin headgear in the winter and I doubt they would if it were dangerous. It would be selected against to say the least (;-)) The birds are worked with tazi dogs in Kazakhstan and are perfectly capable of distinguishing what is quarry, as are most trained hunting birds.
Goldens EASILY kill animals the size of roe and North American pronghorn-- the second is almost routine in winter. They don't have to carry them- they feed in place.
Brian Schmidt said
That might be because the eagles try it on humans only rarely, but whenever the eagles do try it, they succeed. Those might be the solo mountaineers who never returned to tell their tale.
I hope that it is not so.
I've read that in India some villagers in tiger territory wear eyed masks on the back of their head to deter tiger attack (tigers reputedly preferring to attack humans only from behind). Perhaps there is some gear or garb devisable for climbers to deter eagle attack? (Adaptable too for livestock protection?)
Of course. If you were halfway familiar with vertebrate anatomy, you'd understand why. I'll say it again: Read more. Read lots more. And then come back. You have no idea how much evidence against your speculations exists.
It is an inductive inference -- an idea.
OT: Ok, now I got it, I said 'basal pterosaurs' but I meant 'arboreal archosaurs' (probably coastal) from which both birds and pterosaurs derived, IMO.
And there we have your problem: you have yet to learn that you simply can't talk about a topic if you don't know anything about it.
Birds and pterosaurs are not close relatives at all. The birds are closer to Triceratops than to the pterosaurs. We know quite precisely what the closest known relatives of the birds are, and those animals are neither arboreal nor coastal nor basal archosaurs. You can't simply act as if knowledge didn't exist just because it happens not to have reached your eyes yet.
Darren, you may have already seen Scott Maruna's evidence for "Avian Abduction" as written up here: http://biofort.blogspot.com/2008/01/avian-abuctions-back-in-news.html
He also collected a series of newspaper accounts of eagles attacking children, one of which ended with the death of an infant whose skull was opened and the brains eaten before the eagle could be driven away.
Speaking of vultures attacking humans:
Griffon vulture attacks Ipswich woman (at a zoo in the Canary islands, not in the wild).