Groomed By A Vulture

Taken and modified from Wikipedia Commons.

American Black Vultures (Coragyps atratus) are remarkable opportunists. With meathook-like beaks adapted for hooking and slicing, they have the functional morphology of obligate scavengers (Hertel 1995)†, but they'll also take eggs, plant material, garbage, and live prey (Kauffman 2001). Groups have been observed preying on skunks and opossums (McIlhenny 1939) and even juvenile sheep and cattle (Humphrey et al. 2004). The frequency of livestock depredation isn't clear‡, as Avery and Cummings (2004) note that many supposed depredation events are inferred from vultures feeding on already-dead animals; vultures will aggressively pursue afterbirth (Humphrey et al. 2004), which raises the possibility that some 'attacks' are misinterpreted. I'm not attempting to acquit Black Vultures here, but their interaction with livestock clearly requires more study.

† Hertel (1995) doesn't show where C. atratus fits among the scavenger guild, but its extinct relative C. occidentalis tends to be towards the far end of variability. 
‡ This doesn't stop some thousands of Black Vultures from being shot every year - along with hundreds of Turkey Vultures (Cathartes aura) which are not part of this problem (Lebbin et al. 2010). How are these daggers working by the way? I've heard the asterisks were hard to see. I'm also a bit worried when one paragraph will inevitably require three footnotes.

Based on Fig. 1 from Sazima and Sazima (2010).

Similar to the reported events involving livestock, ARKive has video of Black Vultures eating Capybara afterbirth and attacking juveniles, but the relationship between the species is not simple antagonism. Sazima (2007) reviewed video evidence from São Paulo which showed vultures pecking at resting Capybaras, visibly removing ticks and probable organic debris, and the giant rodents changing their posture to allow for a more thorough cleaning. The vultures were also observed to peck at sores (Sazima 2007), but it doesn't seem clear if this was a beneficial removal of necrotic tissue (as the author seemed to imply), or the vultures testing what they could get away with. As for how the association between Black Vultures and Capybaras was formed, Sazima (2007) suggested that the vultures would be familiarized with Capybaras from pecking at the sores and ectoparasites of dead or dying individuals, trying their luck with resting and healthy individuals, being denied when their behavior becomes harmful, learning to seek out resting Capybaras as a food source, Capybaras having advantageous health as a result of grooming, Capybaras adopting soliciting postures, and then cultural transmission in Capybara populations. Sazima and Sazima (2010) mentioned an interesting incident where a vulture picking off organic particles and ticks from a resting Capybara and later flew to a site 100 meters away to feed on a roadkill Capybara, supporting the proposed link between feeding on carrion and grooming (it would have been perfect if the order was reversed...).

Sazima (2010) recorded a remarkable incident involving Black Vultures in São Paulo preening an Irish Setter, the only known instance of cleaner birds interacting with a terrestrial carnivore. Sazima (2010) suggested that the Black Vulture-Dog association could roughly parallel the Capybara situation - the vultures locate the dog resting, spot organic debris in the dog's fur (possibly from rolling on carcasses), approach the dog and begin to feed on organic debris in its hair, and have the dog tolerate their activity until it felt disturbed or was hurt. The dog receptive towards grooming was also recorded to playfully interact with a group of vultures (Sazima 2010), making me wonder if the dog felt preening was play as well. It is unknown if this interaction is localized and/or rare, or if it has been overlooked due to its unpredictable nature and/or lack of attention (Sazima 2010).

Zamuro quitándole parásitos a un Caricare encrestado from Flickr user barloventomagico.

Intraspecific allopreening has been widely observed in birds (including vultures), however interspecific allopreening is a rarity, and has mostly been observed in cowbirds (Palmeira 2008 - citing various). Palmeira (2008) observed Black Vulture/Southern Caracara (Caracara plancus) grooming/preening in Mato Grosso do Sul, Brazil; the Caracara solicited with a head-down display, and subsequently the birds began to simultaneously groom one another. Similar events have been reported from Minas Gerais, Brazil (Souto et al. 2009) and Texas (Ng and Jasperson 1984). The above photo appears to show similar behavior in Venezuela. It would then seem probable that this behavior occurs wherever Black Vultures co-exists with Caracara plancus and C. cheriway, which would be everything from Tierra del Fuego to the southern US.

So why does this behavior occur? Ng and Jasperson (1984) suggest a parallel with cowbirds, which also use a head-down display, in that it could allow Caracaras to join a Black Vulture flock for feeding and roosting. Souto et al. (2009) further suggest that mixed flocks could have the benefits of increased surveillance, the ability of Caracaras to vocalize alarm calls would benefit Black Vultures, and the ability of Black Vultures to locate carrion would benefit Caracaras. I'm curious as to why Caracaras demonstrate this apparent social association-building behavior with Black Vultures and not Turkey Vultures, as the latter has also been observed to intraspecifically allopreen (Souto et al. 2009 - citing Harrison 1965) and is apparently better at finding carcasses (probably by olfaction), even buried ones (Smith et al. 2002). It's worth noting that Sazima (2007) suggested that the long and slender bill of Black Vultures, capable of tearing flesh from small carcasses and catching live insects, makes them excellent pickers and thus potential cleaners. I suspect, for whatever reason, Black Vultures have a propensity towards grooming and aren't particularly fussy about their clientele.




As for why Black Vultures don't go around grooming everything - say (to tie up loose ends) livestock - maybe only a few population in Brazil have learned that preening large mammals results in food. Alternately, Black Vultures could be preening everything that doesn't put up much of a fuss, but such incidents have yet to be recorded in the proper literature.





References:


Avery, M. L. and Cummings, J. L. (2004). Livestock Depredations by Black Vultures and Golden Eagles. Sheep & Goat Research Journal 19, 58-63. Available.


Fisher, H. I. (1944). The Skulls of the Cathartid Vultures. The Condor 46(6), 272-296. Available.


Hertel, F. (1995). Ecomorphological indicators of feeding behavior in recent and fossil raptors. The Auk 112(4), 890-903. Available.


Humphrey, J. S., Tillman, E. A., and Avery, M. L. (2004). Vulture-Cattle Interactions at a Central Florida Ranch. Proceedings - Vertebrate Pest Conference 21, 122-125. Available.


Kauffman, K. (2001). Lives of North American Birds. Houghton Mifflin Harcourt.


Lebbin, D. J., Parr, M. J., Fenwick, G. H. (2010). The American Bird Conservancy Guide to Bird Conservation. University of Chicago Press.



McIlhenny, E. A. (1939). Feeding habits of black vultures. Auk 56, 472–474.


Ng, D., and Jasperson, B. D. (1984). Interspecific Allopreening Between Crested Caracara and Black Vulture. The Condor 86, 214-215. Available.


Palmeira, F. B. L. (2008). Allopreening behavior between Black Vulture (Coragyps atratus) and Southern Caracara (Caracara plancus) in the Brazilian Pantanal. Revista Brasileira de Ornitologia 16(2), 172-174. Available.


Sazima, I., and Sazima, C. (2010). Cleaner birds: an overview for the Neotropics. Biota Neotropica 10(4), 183-194. Available.


Sazima, I. (2010). Black Vultures (Coragyps atratus) pick organic debris from the hair of a domestic dog in southeastern Brazil. Revista Brasileira de Ornitologia 18(1), 45-48. Available.


Sazima, I. (2007). Unexpected cleaners: Black Vultures (Coragyps atratus) remove debris, ticks, and peck at sores of capybaras (Hydrochoerus hydrochaeris), with an overview of tick-removing birds in Brazil. Revista Brasileira de Ornitologia 15(3), 417-42. Available.


Smith, H. R., DeGraff, R. M., and Miller, R. S. (2002). Exhumation of Food by Turkey Vultures. Journal of Raptor Research 36(2), 144-145. Available.

Souto, H. N., Franchin, A. G., and Júnior, O. M. (2009). New Records of Allopreening Between Black Vultures (Coragyps atratus) (Ciconiiformes: Cathartididae) and Crested Caracara (Caracara plancus) (Falconiformes: Falconidae). Sociobiology 53(1), 125-129. Available.

On the Importance of Vultures

Torgos - of no relation to Manos. Taken from here.

Our anthropocentric stigma against scavengers is totally underserved and in fact, carrion consumption is a valuable ecological "service". The word "scavenger" is used fast and loose in popular parlance but the label should be restricted to animals which depend heavily on carrion; just about every vertebrate which can consume meat (including many "herbivores") won't hesitate to snack on a corpse here and there - even humans. The three independent lineages of vultures have specialized for locating and feeding on carrion and utilize the resource to the degree that they can be known as "obligate scavengers" - although it should be noted that it is not their sole food source.

Just to get the word out, nothing said in this article applies to the so-called "Palm-nut vulture" Gypohierax angolensis which is specialized for eating palm nuts (!) and feeds on fish (!!), live prey, and then carrion to a lesser extent (Mundy et al. 1992). Gypohierax is closely related to the gypaetine vultures (both fairly aberrant)... but also Polyboroides and Eutriorchis (Griffiths et al. 2007, Lerner and Mindell 2005). Oh, and the whole "New World"/"Old World" schism is a false dichotomy as these vultures didn't pay attention to those biogeographical rules earlier in their evolution. Anyways, back to the post:

Carrion is an ephemeral and unpredictable resource so it is no surprise that the vertebrates which depend on it the most can fly. Vultures all have large wingspans and locomote by soaring flight (Ruxton and Houston 2004); their stomach acid has a very low pH (1) and is apparently capable of resisting/detoxifying bacteria (Sekercioglu 2006); bald heads and necks don't correlate well with messy feeding habits (contra Mundy et al. 1992) but function along with postural changes as a thermoregulatory mechanism vital to these birds which may deal with rapidly-changing temperatures ranging from <0>70 °C (due to altitude) (Ward et al. 2008). Hertel (1995) outlined the morphological traits shared by these lineages: the long, narrow, shallow, and highly curved maxilla is designed for hooking or slicing large chunks of meat (comparable in function to a meathook); the deep ramus is an adaptation for dorsoventral forces correlated with rapid consumption; there is a large angle between the foramen magnum and basicranium reflecting the strait line of pulling force of the head and neck (avivores, in comparison, have an angle approaching 90 degrees); the narrow ramus and shallow mandibular symphysis indicate a lack of resistance to struggling prey; the occipital distance is greater and orbits are smaller (scavengers are less dependant on eyesight, apparently).

First: Accipiter cooperi - modified from here. This species is a functional avivore and contrasts strongly in form and function with the scavenger lineages. Hertel (1995) compared them to staplers or churchkey can openers function-wise.

Second: Neophron percnopterus - modified from here. A member of the gypaetine vulture lineage(s?). Skull indices of this species and one of its extinct North American relatives (Neophrontops americanus) are well into the "scavenger" ecomorph range despite the extant species taking a broad range of food in addition to carrion (Hertel 1995, Mundy et al. 1992).

Third: Gyps tenuirostris - modified from here. An aegypiine vulture - of all the 13 species in this lineage the 8 Gyps are the most specialized for scavenging (Mundy et al. 1992).

Fourth: Coragyps atratus - modified from here. A member of the cathartid lineage; they're distant relatives of the other vulture lineages but it isn't clear to what degree.

Although functionally similar, there are distinct lineages of gypaetine, aegypiine, and cathartid vultures. The birds which can be called gypaetine vultures are abarrent scavengers; Gypaetus barbatus feeds mostly on bone marrow (it appears to retain vulture-like skull indices despite this); Neophron percnopterus keeps a low profile at large mammal carcasses, is an important small animal scavenger/predator, feeds on eggs, and also consumes fecal matter (preferring carnivore and... human) (Mundy et al 1992). The gypaetine vultures are more basal in the order Falconiformes/Accipitriformes and appear to be allied to the pernine kites; the more familiar aegypiine vultures are more derived and have been recovered in a position somewhere near some of the serpent eagles (long story - see Griffiths et al. 2007 and Lerner and Mindell 2005). Cathartids are, well, certainly not storks and are either basal member of Falconiformes/Accipitriformes (also a long story) or a distinct (ordinal-level?) clade located nearby in a huge mess (see Livezey and Zusi (2007) & Hackett et al. (2008) for the former placement - Morgan-Richards et al. (2008) (and similar mtDNA studies it cites) for the latter).

I think we have been sufficiently introduced to vultures.

So just why is scavenging important? It isn't just some biological curiosity - most animals die from causes unrelated to predation and most of their biomass is consumed by vertebrates (and not microbes and invertebrates) (Devault et al. 2003). Turkey vultures (Cathartes aura) were observed to scavenge every experimentally placed carcass (which wasn't badly decomposed) in a forested environment within three days and vultures on the Serengeti have been observed to consume most of the large, conspicuous carcasses (Devault et al. 2003 - citing Houston 1979, 1986, 1988). So forget the image of vultures cleaning up after lions on the savannah - they consume staggering amounts of biomass from carcasses the size of mice to elephants in temperate and tropical environments worldwide (except Australia...).

It is unfortunate that the loss of Gyps vultures in South Asia due to diclofenac poisoning has demonstrated just how important they were in the ecosystem. The near-extinction of the vultures caused an explosion in the feral dog and rat population and the potential for disease could impact domestic animals and humans (Pain et al. 2003, Prakash et al. 2005). Interestingly, while the importance of facultative scavengers cannot be overstated, these scavengers (such as crows, gulls, starlings) lack the ability to deal with pathogens present in vultures and are more prone to spreading them (Blanco et al. 2006).

Although it appears that vultures are important ecosystem players, facultative scavengers seem to get the job done without them in boreal areas, Australia, and some islands. Perhaps areas with relatively low terrestrial production simply can't support the needs of obligate scavengers and the more generalized species wholly exclude them. The fossil record before the K/T event does not appear to show a community of vulture analogues as none of the pterosaurs and basal birds (that I'm aware of!) show the characteristic skull indices outlined by Hertel (1995) - so presumably a wide variety of facultative scavengers can cover for vultures even in areas with high production. Whatever was going on, in a good portion of our world today vultures are vital parts of the ecosystem and their worldwide decline could be disastrous for a number of as-yet unseen reasons.

Obligate scavengers will even eat facultative scavengers.

Photo taken from here.

References:

Blanco et al. 2006. Faecal bacteria associated with different diets of wintering red kites: influence of livestock carcass dumps in microflora alteration and pathogen acquisition. J. Appl. Ecol. 43, 990–999.

DeVault, Travis L. et al. 2003. Scavenging by vertebrates: behavioral, ecological, and evolutionary perspectives on an important energy transfer pathway in terrestrial ecosystems. Oikos 102, 225-234

Hertel, Fritz. 1995. Ecomorphological Indicators of Feeding Behavior in Recent and Fossil Raptors. The Auk 112, 890-903.

Griffiths, Carole S. et al. 2007. Phylogeny, diversity, and classification of the Accipitridae based on DNA sequences of the RAG-1 exon. J. Avon. Biol. 38, 587-602

Hackett, Shannon J. et al. 2008. A Phylogenomic study of Birds Reveals Their Evolutionary History. Science 320, 1763-1768.

Lerner, H. R. L. and Mindell, D. P. 2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Mol. Phyl. Evol. 37, 327-346

Livezy, Bradley C. and Zusi, Richard L. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zool. J. Linn. Soc. 149, 1-95

Morgan-Richards, Mary et al. 2008. Bird evolution: testing the Metaves clade with six new mitochondrial genomes. BMC Evolutionary Biology 8

Mundy, Peter et al. 1992. The Vulture of Africa. Academic Press

Pain, D. et al. 2003. Causes and effects of temporospatial declines of Gyps vultures. Asia. Cons. Biol. 17, 661–671.

Prakash, V. et al. 2005. Catastrophic collapse of Indian white-backed Gyps bengalensis and long-billed Gyps indicus vulture populations. Biol. Cons. 109, 381–390.

Ruxton, Graeme D. and Houston, David C. 2004. Obligate vertebrate scavengers must be large soaring fliers. Journal of Theoretical Biology 228, 431-436

Sekercioglu, Cagan H. 2006. Increasing awareness of avian ecological functions. TRENDS in Ecology and Evolution 21, 464-471

Ward, Jennifer et al. 2008. Why do vultures have bald heads? The role of postural adjustment and bare skin areas in thermoregulation. Journal of Thermal Biology 33, 168-173.

Whelan, Christopher J. et al. 2008. Ecosystem services provided by birds. Annals of the New York Academy of Sciences 1134, 25-60

Change has come to The Lord Geekington

As you may have noticed, the banner has undergone something of an art evolution. Since I drew the old banner last year I've taken an art class and wow, what a difference it has made! I would love to take more, but now that I have a hypothetical B.S. Biology degree this may prove difficult. We'll see how it evolves next year.

So who's on it?

Discussed here, this is a damaged cat skull (note the missing upper right canine) which I dug up in the woods near my house. The odd characters (sagittal crest, closed postorbital bars) may be related to large size; while I can't rule out an exotic hybrid, this is probably within the range of variation for house cats. I certainly won't let myself fall prey to phylogenetic roulette!


The last thoracic vertebrae and first two dorsal vertebrae from Basilosaurus cetoides, an Eocene stem-cetacean. As I discussed here, the vertebral count from a smaller relative suggests that B. cetoides was even larger and more ridiculously elongated than previously imagined. I'd love to see how these big, extreme vertebrae worked.


Mesoplodon densirostris - I've written quite a lot of posts about beaked whales so a representative is obligatory.

The start of my lazy bird silhouette series, this is a generalized frigatebird (Fregata sp.). They're incredible fliers and I would love to see them in real life.

Turkey vultures (Cathartes aura) are ubiquitous but amazing animals none the less. I saw one getting mobbed the other day and they're capable of some incredibly spry moves for animals that spend most of their time soaring. I've written about cathartids numerous times.

The cirroctopod Opisthoteuthis is the closest an organism has come to resembling a plush animal. They're frequently mentioned in my numerous cephalopod posts. I can't talk about the fish, just some poeciliid of no consequence.


No, it isn't an exogorth, this is an amphibian known as a caecilian. They're the most poorly known major tetrapod clade and their relation to other lissamphibians still seems up for debate. The structure located between the rudimentary eye and the nostril is a sensory tentacle. I have yet to seriously discuss them.


Softshell turtles (Trionychidae) are highly derived cryptodires which traded in a bulky carapace for their titular comparably strong and flexible shell. I've mentioned them here.

Wow, no references. I'll have to make up for that...

Teratorns

I had previously mentioned teratorns all the way back here, noting that family Teratornithidae is grouped with the New World vultures (Cathartidae) - possibly in the order Cathartiformes. The "possibly" is partially due to the fact that traditional grouping in Falconiformes or Ciconiiformes has been challenged and cathartids may require their own order. It should be mentioned that some workers feel that they may be more closely related to storks or Pelicaniformes, but unfortunately there seems to be a lack of available information. Welcome to the world of teratorns!

Teratornis merriami was a Pleistocene teratorn of North America that recently had isotopes from its collagen analyzed by Fox-Dobbs et al. 2006. 2H isotope levels possibly suggested a marine diet in one specimen, but 13C and 15N isotope levels suggest teratorns fed in a terrestrial c3 environment (i.e. the non-arid plants). The 15N isotope levels suggested a mixed diet of browsers and grazers, and the authors suggested the teratorn was a scavenger with wide dietary flexibility due to its size. The authors appear to have assumed that teratorns were obligate scavengers by their large numbers in the tar pits, but of course carnivorous birds will engage in facultative scavenging. If teratorns were large enough to require a broad diet, then perhaps they exploited the tar pits in great numbers despite usually preying on something else. I say preying because two morphological studies cited by Fox-Dobbs et al. strongly suggest just that.

Campbell and Toni 1983 mention a 1981 study by them (which I can't access) documenting the plane of rotation of the quadrates, maxillary rostrum and mandible structures and concluded that the birds swallowed prey whole and could not tear pieces off a carcass like a vulture. Hertel 1995 used a number of indices to classify avian skulls into ecomorphs; scavenging species were well separated from other ecomorphs with fairly high confidence (caracaras were somewhat hard to determine) and were marked by such distinctive features as smaller orbits, greater occipital distance, a deep and narrow ramus, large foramen magnum angle and other features related to twisting food off from a carcass and eating it quickly (and apparently less need for acute vision). Teratorns did not show these vulture-like features and in many features it was classified as a piscivore - except for mandibular and maxillary indices (which apparently classified it as a scavenger and mammalivore/generalist, respectively). Hertel speculates that it could have fed from fish from the surface (the feet were not strongly raptorial), but the isotopes from Fox-Dobbs et al. suggest this was either rare or not the case. I think that the mandibular and maxillary features interpreted by Campbell and Toni as being from a predator and the other features resembling a piscivore (and the facultative scavenging) indicate that this was either a generalized species or occupied an ecomorph with no modern counterparts. Fox-Dobbs et al.'s implication that teratorns went extinct directly because of the loss of megafauna is thus probably not correct. Even if it was fairly generalized, it was still fairly large (12.5-15 kg or 27-33 lbs - Campbell and Toni 1983), presumably had fairly large home ranges and was probably more prone to extinction.

Campbell and Toni 1983 further noted that T. merriami* has always been portrayed as a super-condor (this is still true 25 years later) despite the fact that we now know that the skull indices indicated a much different niche. And since when do birds in different families look identical down to the coloration? The post-cranial skeleton apparently shows a mosaic of cathartid, ciconiid and unique features; the flight was apparently condor-like, the pelvis was stork-like and indicated that sustained walking was possible and the stout legs indicated that running was not likely. I'm guessing that this teratorn could have hunted mammals, reptiles and amphibians on the ground and possibly fish in freshwater, although the short legs would have been a hindrance. However it "earned a living", relatives with similar bauplans existed for millions of years.

*Some material from Cuba may indicate that there is another species in the genus, or that there is yet another genus of teratorn (Olson and Alvarenga 2002). This article mentions a "Teratornis" olsoni. Nothing has been published to my knowledge.


The Incredible teratorn (Aiolornis incredibilis) was one of three teratorn species that lived in North America in the late Pleistocene (from the early Pliocene) and was primarily differentiated from T. merriami by its size. Where T. merriami had a 3.5 to 4 m (11-13') wingspan, A. incredibilis was more along the lines of 5-5.5 m (16.5 to 18') and it presumably weighed around 36 kg (80 lbs) or more. Campbell et al. 1999 examined new and old specimens and determined there were enough characteristics to establish a new genus (it was originally in Teratornis) and suggested that Pliocene specimens may actually belong to other species and/or genera. Clearly a lot remains to be discovered and written about this species, Campbell et al. thought that it had distinctive flight capabilities but didn't (probably couldn't) expand upon that. The beak was deeper than Teratornis, although without much skull material nothing about potential ecomorphology has been written. I doubt it was a "super condor" as alleged by some, and presumably it shared the same walking abilities (since Argentavis did...) and specialized on some other food source. It seems dubious that three large generalists could have co-existed in the North American southwest in the late Pleistocene.

As I've been hinting at, the third species in question is Cathartornis gracilis which is very rarely discussed (it is known from two tarsometatarsi). Campbell et al. 1999 discuss it briefly; it is comparable in size to Teratornis but more gracile, although Campbell et al are not convinced it belongs in its own genus. Olson and Alvarenga 2002 mention that more material has apparently been found and Campbell now thinks it is worthy of genus-level distinction. Like the Cuban material, I haven't heard of any publications.

Teratorns aside from Merriam's aren't discussed too frequently, with the exception of the gigantic Miocene Argentavis magnificens from South America. This was the largest flying species of bird with a span of around 7 meters (23 feet) and a mass of around 70 kg (150 lbs) (The azhdarchid pterosaur Hatzegopteryx dwarfed this) and so has received a lot of attention. Campbell and Toni 1983 stated that Argentavis was simply a larger version of the Teratornis morphotype on the basis of wing and leg bone similarities (i.e. condor-like flight and stork-like walking); apparently the 1981 paper by the authors documented features of the 55 cm+ skull which indicated it was predatory (Chatterjee et al. 2007). Palmqvist and Vizcaino 2003 determined that a falconiform the size of Argentavis would have a territory of about 542 square kilometers (~200 sq. miles) and would take about three days to patrol its territory and would eat around 5-10 kg of meat per day. The authors feel that since scavenging birds do not have defined territories and can exist at higher densities that predatory ones - and they suggest that predatory sabertoothed marsupials opened up a new niche for giant vultures (they seemed to imply that Argentavis ate bones). Most recently, Chatterjee et al. 2007 stuck with the morphological implications that this was a predatory species capable of eating rabbit-size animals whole. So why gigantism? Palmqvist and Vizcaino note that while giant species have low populations, low population density, small clutch size and long breeding cycles they are resilient against predation (maybe even engaging in kleptoparasitism) and can withstand famine.

Very seldom discussed is the earliest teratorn Taubatornis (with 6 Google hits) from the late Oligocene of Brazil that had not reached the proportions of later species (the distal width of the tibiotarsus was about 70% that of Teratornis). This fossil also demonstrates that South America is likely the place of origin for this family and that teratorns in North America (and Cuba?) were a fairly recent phenomenon. Olson and Alvarenga also mention the curious fact that teratorns and cathartids are almost always found together, which would support frequent scavenging habits (the authors are neutral).


That about ends the story for teratorns thus far, and as usual there are more questions than answers. For birds with no obvious adaptations for eating carrion, teratorns sure did hang out with vultures and get stuck in tar pits a lot. Teratorns also seem very different from living birds of prey that hunt on the ground, and exactly how a short-legged bird unable to run well hunts a sufficient number of small animals per day is beyond me. Perhaps Teratornis was somewhat like a marabou stork or adjutant (Leptoptilos sp.) in that it was a presence at kills but otherwise occupied a different niche it was morphologically adapted towards. The presence of three sympatric genera (and their extinction) certainly hints that these were not all generalists. It is increasingly clear that teratorns were not "super condors", but what exactly they were is still rather unclear. Hopefully some of the unpublished material will come to light and new discoveries will be made to clear up the basic life histories of this enigmatic group.






References:

Campbell, Kenneth E. and Tonni, Eduardo P. 1983. Size and locomotion in teratorns (Aves: Teratornithidae). The Auk 100: 390-403.

Campbell, Kenneth E. et al. 1999. A New Genus for the Incredible Teratorn. Smithsonian Contributions to Paleobiology No. 89: 169–175. Available (Huge file)

Chatterjee, Sankar et al. 2007. The aerodynamics of Argentavis, the world’s largest
flying bird from the Miocene of Argentina. PNAS. Published online (for free)

Fox-Dobbs, Kena. 2006. Dietary controls on extinction versus survival among avian
megafauna in the late Pleistocene. Geology V. 34, No. 8 pp. 685-689

Hertel, Fritz. 1995. Ecomorphological indicators of feeding behavior in Recent and fossil raptors. The Auk 112(4): 890-903

Olson, Storrs. L and Alvarenga, Herculano M. F. 2002. A new genus of small teratorn from the Middle Tertiary of Taubate Basin, Brazil (Aves: Teratornithidae). Proceedings of the Biological Society of Washington 115 (4) pp. 701-705

Palmqvist, Paul and Vizcaino, Sergio F. 2003. Ecological and reproductive constraints of body
size in the gigantic Argentavis magnificens(Aves, Teratornithidae) from the Miocene of Argentina. Ameghiniana 40 (30) pp. 379-385

New World Old World Vultures?

Quite a while ago I discussed the fossil history (and perhaps origin) of the cathartids or "New World" vultures in the Old World - and hinted at a "tale for another day". The cathartids are of rather uncertain taxonomic placement (a distinct order?) while the "Old World" vultures are placed in order Falconiformes* in the family Accipitridae and sub-family Aegypiinae. BUT - and there always is one regarding classification these days - this should be "Aegypiinae" since genetic evidence suggests that Gypaetus (Bearded vulture), Neophron (Egyptian vulture), Gypohierax (Palm-nut vulture) and perhaps Polyboroides (Harrier-Hawks) form a clade rather distanced from the remaining 6 genera of "vultures" (Griffiths et al., 2007). So Aegypiinae is apparently both para- and polyphyletic, huh. As the photos suggested, the three genera of "vultures" are superficially rather aberrant looking so perhaps this is not too much of a shock. Siebold & Helbig 1995 suggested the sub-family Gypaetinae for Gypaetus and Neophron; and I'll use Aegypiinae for the remaining and more conventional "vultures".

*Or Accipitriformes, Griffiths et al. 2007 placed Falco pretty far away. I probably shouldn't get into this.


Why go through all this trouble? Reportedly, both Gypaetinae and Aegypiinae have occupied the New World at some point of time. This is rather remarkable on top of the vulturids/cathartids living there and caracaras (Polyborinae). Marabou stork relatives (Leptophilini) were also present, but there's nothing to suggest they were scavengers (Jabiru isn't). Oh and teratorns don't appear to have been scavengers, despite their common depiction as super-condors.

Anyways, let's take a look at these New World Old World vultures:


Gypaetinae

Neophrontops is a genus with five species related to Neophron that lived in North America from the mid-Miocene to upper Pleistocene (Fedducia, 1974), so it certainly did not have a very casual appearance. I should note that Fedducia's described species, Neophrontops slaughteri, was named for, ehem, one Bob Slaughter. Fedducia's vulture species did not appear to overlap chronologically but a later study (Rich, 1977) showed that two species (N. americanus and N. vallecitoensis) were both present in the mid-Pleistocene with different sizes (the latter was larger); this could make it a radiation of sorts, albeit a rather brief one. Fedducia notes that Neophron fossils have not been found in Africa (this still appears to be true) and suggests that, gulp, the current species is the result of an invasion of Old World vultures to the Old World from the New World perhaps as recently as the Pleistocene. The genetic grouping with Old World species may not be entirely inconsistent, although it would require this lineage to be oddly invasion prone.


Aegypiinae?

While the Neophron/Neophrontops relation appears to be rather unambiguous one, larger reported New World Old World vultures are rather, well, problematic. Two genera have been classified in Aegypiinae: Palaeoborus and Neogyps. In the description of a new Palaeoborus species by Miller & Compton 1939, it (well, its ulna) is noted as being similar to Neogyps except for differences in the shape of the condyle; oh and it is somewhat comparable to Haliaeetus. Why does this stick out to me? Hertel 1995 notes that Neogyps, the "Errant eagle" was originally considered an eagle with vulturine habits, then re-classified in Aegypiinae; but skull indices used to determine diet classified it as a mammalivore, possibly a generalized one. I unfortunately couldn't find Patricia Rich's book on the subject of fossil vultures, but the book The Origin and Evolution of Birds* by Alan Fedducia (partially available here, p. 299-300) notes that she couldn't conclude on their relations and raised the possibility that they are one or more separate branches of hawks or eagles.

*Oh, and it mentions that Ciconia maltha was the ecological equivalent of the marabou stork. I haven't seen this confirmed elsewhere.


I haven't seen any more recent work on the phylogenetics of these species, although that would be difficult seeing as how Accipitridae is currently undergoing upheavals. Are the genera related? Palaeoborus is from the Upper Miocene to Lower Pliocene and Neogyps is from the Upper Pleistocene (Fedducia, 1974), so there is only a mild ghost lineage. Fedducia hinted at the possibility of Old World vultures having New World origins, but we'd have to assume that eagle-like characteristics were due to the basal nature of the genera. These seem to be rather ambiguous species here, so it doesn't seem as if we can do much aside from speculating on their relations. I guess for now that we'll have to conclude that there is no unambiguous evidence for New World members of Aegypiinae.


Not having Rich's book has made this post difficult, but it appears that nothing more definitive can be known. I for one thought things were a little more definitive before starting this post for one thing, but I learned better. Well, at least we got New World Old World "vultures" of a sort.

Next time I think I'll blog on something less old and ambiguous.

-Cameron

References:

Fedducia, Alan. 1974. Another Old World Vulture from the New World. The Wilson Bulletin. Vol. 83, No. 3. Available (for free).

Griffiths, Carole S. et al. 2007. Phylogeny, diversity, and classification of the Accipitridae based on DNA sequences of the RAG-1 exon. J. Avian Biol. 38: 587- 602.

Hertel, Fritz. 1995. Ecomorphological Indicators of Feeding Behavior in Recent and Fossil Raptors. The Auk, Vol. 112, No. 4., pp. 890-903.

Miller, Alden H. & Compton, Lawrence V. 1939. Two Fossil Birds from the Lower Miocene of South Dakota. The Condor, Vol. 41, No. 4., pp. 153-156.

Siebold, Ingrid & Helbig, Andreas. 1995. Philosophical Transactions : Biological Sciences, Vol. 350, No. 1332, pp. 163-178

Rich, Patricia Vickers. 1977. Temporal range extension of Neophrontops americanus (Accipitridae). The Condor, 79: 494-509. Available (for free)

The Yellow-Headed Vultures

Dear Constant Readers,

This is not actually new, but an expanded last half of the previous post. It was just getting too cumbersome or "epic" and I think the tone of this is different enough to warrant splitting. I finally did get a good source on these species too, so they won't be as spotty. As always, don't hesitate to correct me on anything.

Contrary to just about everything written about birds, they do not have a rudimentary/absent sense of smell (Beason 2003). Uniquely among aegypiines, cathartids, and probably just about every other avian, members of the genus Cathartes detect the chemical ethanethiol which is produced by rotting corpses. Even fairly close relations such as the black and king vulture conspicuously lack this ability. Additionally, Cathartes cathartids are all large, dark birds with two-toned wings and brightly colored heads.



Cathartes melambrotus
Greater Yellow-Headed Vulture
Forest Vulture

Interestingly, this was by far the last known extant cathartid to be named, all the way back in 1964. The animals themselves were assumed to be a race of C. burrovianus; but differences in size, head color, range and habitat were enough to convincingly make this a distinct species (Amadon, 1977). The IUCN Redlist states that this species inhabits subtropical rain forest and is of least concern despite a downwards population trend. Their range is 6.7 million square kilometers (~2.5 million square miles), which is the smallest of any non-condor cathartid. The population is estimated at 100,000 to 1,000,000 animals, roughly the same as most non-condors excluding turkey vultures. Unfortunately there do not appear to be many recent publications on this species, so I'm going to have to rely on some more popular material.


The book "Raptors of the World" gives this range, about 3-4 million square kilometers/1.1 to 1.5 million square kilometers. Confusingly the IUCN cites this book as a reference, so it is possible new data subsequently came out to support a larger range. The whole of South America is, by the way, about 6.8 million square miles/17.8 million square kilometers. Given that it is common over its range and nearly replaces turkey vultures, Ferguson-Lees and Christie feel the 6-figure estimate is justified. Presumably it is on the lower side of that broad estimate. They also feel that it is potentially threatened with deforestation. The name (which unfortunately hasn't caught on) indicates that this bird is specialized to living in tropical to near-temperate primary forest in lowlands but also some adjacent grasslands. They range vertically from sea level to 1000 meters/3200 feet (normally over 700m) but can be found as high as 2000 meters/6500 feet.

Despite the name, as you can see from this illustration, the heads of these birds are not exclusively yellow, but have a blue crown and blue spot in front of the eyes. The overall coloration of the head varies into yellow-orange with the crown varying into gray and pink. Irises on this species are red. The plumage is black with a variable greenish to purplish tinge. The two-toned underwings of this genus are the least pronounced in this species. This species is similarly sized to the turkey vulture but has wider wings which are held flat or in a slight dihedral and the rocking behavior while soaring is not exhibited. These birds are solitary or travel in pairs, but have been known to roost which turkey vultures, whom they dominate at kills. There is little information known about food and breeding.

I have noticed that some recent movies (Big Fish, Sideways deleted scene) have used this species in lieu of the turkey vulture. Apparently there is some sort of protective law for the native turkey vulture against using it, but not for this species. It was definitely odd to see such an obscure species in major films.

Additionally, this page has some videos, this one has photographs and discusses differences with the lesser yellow-headed vulture.



Cathartes burrovianus
Lesser Yellow-Headed Vulture
Savannah Vulture

According to the IUCN this species is also of "least concern" and occupies a territory of 7.8 million square kilometers (~3 million square miles) of grasslands, wetlands, and degraded former forest. The territory occupied is still much less than most non-condor cathartids. "Raptors" cites a figure of 12 million square kilometers, but estimates that 2/3rds of that is unsuitable and the rest is patchily distributed. Marsh, coastal swamps, mangroves, grasslands, open woodlands, rice fields and urban areas are inhabited, but not forest. It also engages in nomadic wanderings and migrations. Despite all these difficulties in measuring population, the authors still feel it is probably in the 6-figures somewhere. The map included is of course a vast simplification of the distribution:

As one can see from this illustration, "yellow-headed" is a bit of a misnomer for this species. The head ranges from yellow to orange and the neck and crown are sometimes red. The crown and neck can also vary to blue-gray, blue-green, or violet. The wings are two-toned, but the tips are noticeably lighter colored for a member of the genus. Feathers are blackish with a green tinge but wear away into a brown color. An additional field characteristic is that while on land, the wings are held in a way that makes them appear much longer than other Cathartes. Unlike the forest vulture and like the turkey vulture, this species flies with a dihedral and characteristic "rocking". It apparently does not soar as high as the turkey vulture though.

These birds are also solitary, in pairs, or rarely in groups. There was at least one report of hundreds flying in a possible seasonal migration however. As far as food, they tend to avoid large carcasses and go for smaller mammals, reptiles, and amphibians. Given that it often lives in wetlands, dead fish are commonly eaten. Invertebrates, their larvae, and frogs may be eaten alive.

Unlike the forest vulture, this species is believed to have some geographical variation. Individuals increase in size eastwards and southwards and tend to have straw colored primaries. Some authorities treat them as Cathartes burrovianus urubitinga. They have also been seen in more northwestern portions, but this may be due to seasonal migration.



As you can see from this information, there really are a number of uncertainties about these two species. Other cathartids are better known, but this demonstrates how for every common species there seem to be a few neglected ones. This isn't the last we'll hear about cathartids, but who knows what things I'll move on to next...


-Cameron


References:
Some free, some not.

Beason, Robert C. 2003. Through a Bird's Eye - Exploring Avian Sensory Perception. Bird Strike Committee Proceedings. Published online (for free) Here

BirdLife International 2004. Cathartes burrovianus. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 18 July 2007.

BirdLife International 2004. Cathartes melambrotus. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 18 July 2007.

Ferguson-Lees, James and Christie, David A. Raptors of the World. Houghton Mifflin, New York, 2001.

Vulture Mimics: An Introduction to Cathartids

I'll level with you, cathartids actually aren't vulture mimics, vulture originators would technically be more appropriate. Technicalities such as earlier fossil/implied genetic age aside, the "Old World" vultures were known to the West much earlier (obviously) and still remain the by far the most popular conception of what a "vulture" is*. Why is this important do you ask? For instance, ostrich-mimics (ornithomimosaurids) are older than ostriches, but unfortunately they were discovered later and are less familiar. There is even a non-dinosaurian ostrich-mimic-mimic (Effigia) that is even older and less familiar still. While cathartids are often called "New World" vultures, as we'll see that is a very poor name indeed. I won't call them vulture mimics either, that was just a scam to initiate discussion, I'll call them cathartids**. But as we'll see...

*Actually the genus Gyps (Griffin vultures) seems to be the long-necked "vulture" archetype. Ever notice how in cartoons taking place in the American West the vultures are all Griffins? Vultures most certainly are not limited to deserts either, by the way. Aegypiine vultures have some interesting forms and classification controversies, they might get discussed later.

**According to Amadon 1977, at least one authority called the whole group "condors".


Some sources such as Mikko's phylogeny put cathartidae and vulturidae as synonyms. Curiously I've noticed that papers on condors (e.g. Vultur) classify them as vulturids but just about everything else calls them cathartids (e.g. Cathartes aura, the turkey vulture). I suspect vulturidae may be a functional sub-family in most classifications, but I have yet to find a source specifically stating this [Edit: "Vulturid" is a synonym with priority nonetheless. However, it likely that it was named with "old world" vultures in mind. See comments]. The big-picture classification of cathartids is more confusing still. Traditionally they were classified as falconiformes along with the familiar birds of prey. Their overall appearance is similar, although cathartids have odd features such as weak feet and perforate nostrils. The oft-cited Sibley-Ahlquist taxonomy upheaval placed them in the order ciconiiformes along with storks and relatives. To cite something, why not the Turkey Vulture Society page, yep, turkey vultures are more popular than what I'd previously thought. A stork/vulture association isn't as nonsensical as it seems; the shockingly hideous marabou stork is a bald-headed (occasional) scavenger with the same self-urination (the white stuff in bird poop isn't poop) habit of keeping cool. Interestingly, the stork/vulture connection has been suspected as early as 1967 (Fedduccia, 1974). However, it most certainly is yet another vulture-mimic of sorts.

But here's the problem: cathartids aren't ciconiiformes either. Popular literature is often outdated and/or a simplification of controversial issues. As a layman, the world of bird phylogeny seems ludicrously confusing and unsettled. A 2006 paper by Ericson et al places them closer to falconiformes (and near-passerines, apparently) than ciconiiformes, although their split apparently took place slightly before the K/T event. Slack et al in a 2007 paper places them in a super-group called the Cracrafti/Conglomerati, although they are positioned in an unstable area in between the falcon/buzzard, gull/oystercatcher, and albatross/loon/stork/penguin lineages. Another paper by Gibb et al in 2007 again with more species included it the synonymous "water-carnivore" super-group and interestingly placed cathartids closer to the seabirds/shorebirds than anything. However, they are still clearly quite isolated. The phylogenetic trees also demonstrates a surprising distance between falcons and buzzards making falconiformes apparently paraphyletic; and demonstrated storks and pelicans grouping rather than with herons, making the traditional ciconiiformes polyphyletic. With more species getting studied, it seems like birds phylogeny is going to need a radical overhaul. Cathartids are now apparently an incertae sedis, although I have seen a proposal for the creation of the order cathartiformes. I've seen this used in a recent Spanish-language publication (here), although widespread acceptance is lacking.

Despite taxonomic upheavals galore the extinct family teratornithidae is still attached to cathartids in recent publications (e.g. Chatterjee 2007). Mikko's phylogeny page places both groups in an encompassing group called vulturides. Usage of that group appears exceedingly rare in publications and I am not certain if it could be synonymous with cathartiformes or not. Despite traditionally being portrayed as super-condors (such as here) tetatorns are now believed to be predatory and distinctive. Given their size (bigger than even super-marabous) they might just be present in the final post of some trilogy.

Let us now discuss cathartids proper, the extinct ones. The reason I don't call cathartids "New World vultures" is that they were certainly present in the Eocene-Oligocene of Europe. To make matters worse, aegypiine vultures are known from both Old and New Worlds from the lower Miocene to Pleistocene, obscuring their "world" of origin (Fedduccia 1974). That's a tale for another day though. Cracraft & Rich in their 1972 paper discuss how for years possible remains of Old World cathartids were discounted or ignored due to their problematic nature (the vice versa was true as well interestingly). Despite their outwards similarity to aegypiines, cathartids are very distinctive from a skeletal standpoint, particularly the shape of the tarsometatarsus and to a lesser degree the tibiotarsus. They named four genera, one of which (Amphiserpentarius) was apparently re-classified as a secretary bird, but according to Mikko's the rest still stand up. [[Edit: Peer editing has revealed to me that the alleged smallest crow-sized cathartid, Plesiocathartes, is a leptosomid. The paper is unfortunately unavailable to me, but see comments]]. The authors raise the remarkable possibility that cathartids in fact originated in Europe in between the late Cretaceous and Eocene and branched out to the New World in the Early Eocene. This was presented as an alternate hypothesis and not a replacement. I haven't seen much more discussion on this, but it should be noted that they used the non-cathartid Neocathartes in their theory. This was alleged to be a "walking turkey vulture" of sorts, but turned out not to be. Sorry for not being able to find the actual paper for that one.

I hope that this was an adequate prelude to the cathartids. There are still some fossil forms that I'll probably cover some time in the future, but I'd like to talk more about extant species. Perhaps I can do a cathartid-of-the-random-time-interval sort of feature. Or maybe not, I like to focus on obscurity...


Oh, I'm not done just yet.


-Cameron


References:
Some free, some not.


Amadon, Dean. 1977. Note on the Taxonomy of Vultures. The Condor. 79: 413-416. Available: Here

Chatterjee, Sankar & Templin, R. Jack & Campbell, Kenneth E. 2007. The aerodynamics of Argentavis, the world's largest flying bird from the Miocene of Argentina. Proceedings of the National Academy of Sciences. Published online (for free) Here

Cracraft, Joel & Rich, Pat Vickers. 1972. The Systematics and Evolution of the Cathartidae in the Old World Tertiary. The Condor. 74: 272-283. Available: Here

Ericson, G.P. et al. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biology Letters. 2: 543-547. Available: Here

Fedduccia, A. 1974. Another Old World vulture from the New World. Wilson Bull. 86: 251-255. Available online Here (for free)

Gibb, Gillian C. et al. 2007. Mitochondrial Genomes and Avian Phylogeny: Complex Characters and Resolvability without Explosive Radiations. Mol Biol Evol. 24: 269-280. Available: Here

Slack, Kerryn E. et al. 2007. Resolving the root of the avian mitogenomic tree by breaking up long branches. Molecular Phylogenetics and Evolution. 42: 1-14. Available: Here