Hornbills, hoopoes and woodhoopoes are all similar in appearance and have been classified together in a group termed Bucerotes. Vague similarities with other long-billed, forest-dwelling birds (like woodpeckers, long-billed cuckoos and such passerines as tree-creepers) meant that early ornithologists were often confused about the affinities of these birds. By the late 1800s, however, most had realised that all three were close relatives, and that they were most likely close kin of kingfishers, bee-eaters and rollers. The group that includes kingfishers, bee-eaters, rollers, hornbills and hoopoes has been termed Coraciiformes; some recent phylogenies have found Coraciiformes of tradition to be paraphyletic to Piciformes (woodpeckers and kin) (e.g., Mayr et al. 2003, Cracraft et al. 2004, Ericson et al. 2006, Hackett et al. 2008). The resulting 'coraciiform' + piciform clade appears robust and has recently been named Picocoraciae (Mayr 2010).
Within Picocoraciae, a close link between hornbills, hoopoes and woodhoopoes is firmly established on the basis of anatomical and genetic evidence. All three groups share a list of features not seen in other birds, and have similar skulls, chest bones and leg bones.
Hoopoes and woodhoopoes are similar, slender-billed birds of Old World woodlands, forests and grasslands [adjacent image shows Green woodhoopoe Phoeniculus purpureus (also called the Purple or Red-billed woodhoopoe): photo by Axel BÃ¼hrmann, from wikipedia]. The Hoopoe Upupa epops [shown at top; photo by J. M. Garg, from wikipedia] is widespread, occurring across Europe, Africa including Madagascar, and Asia. These populations differ somewhat in size and colour and about ten subspecies have been named: some experts think that a second species (U. africana) should be recognised for African hoopoe populations. A large, flightless species (U. antaios) previously inhabited St Helena in the South Atlantic (Olson 1975).
Hoopoes are unmistakeable, combing a long, decurved bill with an erectile crest, pinkish or buff-coloured head and body plumage, and black-and-white striping on the wings and tail. They probe into bark, soil and leaf litter with the long bill, and feed mostly on insects and their larvae. Much of their foraging is done on the ground. Hoopoes are more flexible in terms of nesting behaviour than hornbills and woodhoopoes, and will use burrows, nest boxes and buildings as nest sites. The nest site soon becomes fouled with droppings and food fragments.
Woodhoopoes - some species of which are sometimes called scimitarbills - are restricted to Africa, though they also inhabited Europe during the Miocene (Ballman 1969). Between eight and ten species are known (ideas differ on which populations should be regarded as species: see Simmons et al. (2005) and Cunningham & Cherry (2005)). Most forage in the trees of woodland and grassland environments, but two are restricted to rainforests. Woodhoopoes are hoopoe-shaped, but differ from them in being crestless and in possessing dark, metallic plumage. Some have straight bills, while in others the bill is strongly curved. Several species have white patches on their wings and tails, and the White-headed woodhoopoe Phoeniculus bollei [shown here, painting by J. G. Keulemans] is particularly distinctive.
Woodhoopoes are more agile than hoopoes, and are experts at climbing up tree trunks and clambering about among branches. They even hang upside down on occasion, and often use their tail feathers as props in similar fashion to woodpeckers. When on the ground, woodhoopoes hop, whereas hoopoes walk.
One interesting detail of woodhoopoe biology is that the sexes often differ in bill length, with males having substantially longer, more curved bills (a male's bill can be more than one-third longer than a female's) [adjacent photo - showing bill dimorphism in Green woodhoopoe - from Andrew Radford's site]. Females forage on branches for small insects, while males probe into crevices for larger prey (Jamieson & Spencer 1996, Radford & du Plessis 2003). Sexual dimorphism in bill length and shape is fairly widespread in birds, and it means that the sexes avoid competing with one another by acting as separate 'ecological species' (see the article Sexual dimorphism in bird bills: commoner than we'd thought).
Like hornbills and hoopoes, woodhoopoes are cavity nesters. However, Green woodhoopoes at least cannot use cavities that are open to the elements and require cavities partially covered by bark or vegetation. These partially covered cavities are rare commodities, and are often taken over by bees, rodents and other animals. It also seems that woodhoopoes are sensitive to cool night-time temperatures and ordinarily cluster together under cover to stay warm at night. All of this means that they're constrained in terms of where they can live and breed (du Plessis 1992). [Image below shows Common scimitarbill Rhinopomastus cyanomelas by Steve Garvie, from wikipedia.]
Because woodhoopoes often choose roost or nest sites in weak, partially rotten wood, they are poorly protected from mammalian predators. Genets and cats take a heavy toll on woodhoopoe populations, and woodhoopoe mortality seems to be about twice as high as that of other small birds from the same habitats. Woodhoopoes are not completely defenceless though: female hoopoes and woodhoopoes can both produce a dark, foul-smelling oil when threatened on the nest, and can even spray it from their oil gland (located beneath the tail).
Woodhoopoe family life
Some woodhoopoe species are highly social birds that live in groups with a well-established dominance hierarchy. The Green woodhoopoe is a co-operative breeder, and as many as ten birds will work together with a mated pair to help raise their chicks (du Plessis 1991, du Plessis et al. 2007). As is typical among co-operative breeders, these helpers are often close relatives of the pair, typically being offspring from previous clutches. However, unrelated birds of the same sex may also form social groups, with the non-breeders being subordinate to the breeding, territory-holding birds. It seems that this behaviour is reciprocal, and that the roles are exchanged when the helpers become territory-holders themselves. The breeding behaviour of other woodhoopoe species is poorly known, so it is possible that co-operative breeding occurs in some of them as well.
All individuals of the social group help defend the breeding territory, but the subordinate birds actually seem to contribute more to territory defence than the breeding pair. Groups use 'vocal rallying' (or choruses) to advertise their occupation of a territory, and call for longer when they perceive that a neighbouring group consists of many individuals (Radford 2003). Males undergo a change in voice at sexual dimorphism (Radford 2004) and, because the composition of a group means that it has a distinct rallying sound compared to others, groups can identify other groups with ease. A group answers faster to an unfamiliar group, or to a trespassing familiar group, than to a familiar group in its expected location (Radford 2005).
And, just to remind you what this all would have looked like had the book worked out, here's the layout we planned...
For previous articles on members of Picocoraciae, see...
- She was a very strange woodpecker
- Woodpeckers: barbed tentacles and the avoidance of brain injury
- A case of dead kingfishers
- The other ground hornbill
- Ground hornbills: savannah-dwelling, avian pseudo-hominids
Refs - -
Ballman, P. 1969. Die VÃ¶gel aus der altburdigalen SpaltenfÃ¼llung von Wintershof (West) bei EichstÃ¤tt in Bayern. Zitteliana 1, 5-60.
Cracraft, J., Barker, F. K., Braun, M., Harshman, J., Dyke, G. J., Feinstein, J., Stanley, S., Cibois, A., Schikler, P., Beresford, P., GarcÃa-Moreno, J., Sorenson, M. D., Yuri, T. & Mindell, D. P. 2004. Phylogenetic relationships among modern birds (Neornithes): towards an avian tree of life. In Cracraft, J. and Donoghue, M. (eds), Assembling the Tree of Life. Oxford University Press (Oxford), pp. 468-489.
Cunningham, M. & Cherry, M. I. 2005. Seeing the woodhoope for the trees: a response to Simmons et al. (2005). Ibis 147, 225-227.
du Plessis, M. A. (1991). The role of helpers in feeding chicks in cooperatively breeding green (red-billed) woodhoopoes Behavioral Ecology and Sociobiology, 28 (4) DOI: 10.1007/BF00175102
- . 1992. Obligate cavity-roosting as a constraint on dispersal of Green (Red-billed) woodhoopoes: consequences for philopatry and the likelihood of inbreeding. Oecologia 90, 205-211.
- ., , Robert E Simmons, R. E. & Radford, A. N. 2007. Behavioural ecology of the Namibian violet woodhoopoe Phoeniculus damarensis. Ostrich 78, 1-5.
Ericson, P. G. P., Anderson, C. L., Britton, T., Elzanowski, A., Johansson, U. S., KÃ¤llersjÃ¶, M., Ohlson, J. I., Parsons, T. J., Zuccon, D. & Mayr, G. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biology Letters 2, 543-547.
Hackett, S. J., Kimball, R. T., Reddy, S., Bowie, R. C. K., Braun, E. L., Braun, M. J., Cjojnowski, J. L., Cox, W. A., Han, K.-L., Harshman, J., Huddleston, C. J., Marks, B., Miglia, K. J., Moore, W. S., Sheldon, F. H., Steadman, D. W., Witt, C. C. & Yuri, T. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320, 1763-1768.
Jamieson, I. G. & Spencer, H. G. 1996. The bill and foraging behaviour of the Huia (Heteralocha acutirostris): were they unique? Notornis 43, 14-18.
Mayr, G. 2010. Metaves, Mirandornithes, Strisores and other novelties - a critical review of the higher-level phylogeny of neornithine birds. Journal of Zoological and Systematic Evolutionary Research 49, 58-76.
- ., Manegold, A. & Johansson, U. S. 2003. Monophyletic groups within 'higher land birds' - comparison of morphological and molecular data. Journal of Zoological and Systematic Evolutionary Research 41, 233-248.
Olson, S. L. 1975. Paleornithology of St. Helena Island, South Atlantic Ocean. Smithsonian Contributions to Paleobiology 23, 1-48.
Radford, A. N. 2003. Territorial vocal rallying in the Green woodhoopoe: influence of rival group size and composition. Animal Behaviour 66, 1035-1044.
- . 2004. Voice breaking in males results in sexual dimorphism of Green woodhoopoe calls. Behaviour 141, 555-569.
- . 2005. Neighbour-stranger discrimination in the group-living green woodhoopoe. Animal Behaviour 70, 1227-1234.
- . & du Plessis, M. A. 2003. Bill dimorphism and foraging niche partitioning in the green woodhoopoe. Journal of Animal Ecology 72, 258-269.
Simmons, R. E., Du Plessis, M. A. & Hedderson, T. A. J. 2005. Seeing the woodhoopoe for the trees: should we abandon Namibia's Violet woodhoope Phoeniculus damarensis as a species? Ibis 147, 222-224.
The species in the first picture looks remarkably like a woodpecker.
(Olson, 1975) is available online if anybody wants to read the original description of Upupa antaios: http://www.sil.si.edu/smithsoniancontributions/Paleobiology/pdf_lo/SCtP…
Amazing animals birds are. I just got back from scout camp so I've seen my fair share lately. Is there any hope that this will be published.
Are these exclusively an old world group? I'm very sure I have seen a bird remarkably similar to the one in your first caption building very complex bag-like hanging nests here in tropical America. But then again, I'm no bird expert and I've always seen them from down below in the ground. I think they call these birds 'oropendolas' around here.
I'm pretty sure you saw oropendolas. If you did, those aren't related to hoopoes at all. Oropendolas are icterids, and thus deeply nested in Passeriformes.
To be honest, I don't think oropendolas and hoopoes look at all alike, as unfortunately named 'passerines and near-passerines' go. For one, oropendolas are much larger, much longer-legged, straighter- and thickerbilled, proportionally narrower winged, etc. than hoopoes.
You might have seen them from some distance, though.
Thank you very much for this article! I live in South Africa, and we have hoopoes here (quite frequently visiting our garden) and also Woodhoopoes (green) and Common scimitarbills. The scimitarbill is the only one around the town where I live (most of the country is open savannah); the green woodhoopoe lives in more densely wooded areas. I didn't know about woodhoopoe bills! I haven't seen the green one much; the scimitarbill I gather doesn't have the same degree of sexual dimorphism. Anyways I'd like to say something about the calls ... woodhoopoes are called 'Kakelaars' in Afrikaans which roughly means 'cacklers'; they have a cackling, chattering, rather mocking and jeering sort of call. But the scimitarbill has an entirely different kind of call. It is a simple, plaintive whistle, repeated a few times in succession, and only a single bird utters it, it's not the rallying 'crowd call' kind of thing of the green woodhoopoes. Makes sense since they're pretty much solitary ... well, actually most of the time they're in pairs, but I've seen on occasion three birds in the same vicinity. I would very much like to know whether it is indeed right to classify scimitarbills in a different family from the woodhoopoes ... they are very similar in ways but there are also significant differences. They *look* very much like woodhoopoes but they *act* different.
Regarding your question at the end, there is no objective standard for deciding if two species belong to the same or different families. The standard is indeed "Do they look different enough?", but then the meaning of "enough" is quite undefined. Usually, scimitar-bills are put in Phoeniculidae. But you can do whatever you want: submerge it all in Upupidae, proclaim Rhinopomastidae, whatever. Knock yourself out. Whatever you do, nobody can say you're wrong. The tree of life is an objective reality, but the names we give to its nodes and branches are arbitrary.
Then again, Charles Sibley liked Rhinopomastidae, and he did have an objective standard, though one that's almost impossible to follow rigorously.
I have always wondered that the african hoopoe is regarded as a separate species, but not the madagascar form, since this is much more distinct than the other two.
The Madagascar Hoopoe is significantly larger than other hoopooes (so much that one is immediately struck by its size when first seeing it). It has much paler plumage and a purring call that is very different from the "normal" popping hoopoe call. And perhaps strangest of all, it is a forest bird.
It is quite a shame that the book did not work out. I know I would have bought it.
Tommy: some people have suggested splitting Madagascar form into a third species. However, both other species can often be found in park-like forests. Along the north-eastern edge of hoopoe's range in Russia, it is essentially a forest bird, living in pine forests. African hoopoe prefers wooded campgrounds to open savanna in many national parks. I suspect that the idea that the hoopoe is a bird of the open country is false: it's just easier to see there.
The bird on the left page of the mock layout looks like a toucan!
I've never seen woodhoopoes before. They're pretty excellent.
"They probe into bark, soil and leaf litter with the long bill, and feed mostly on insects and their larvae."
I vaguely remember part of one of the autobiographies about Gerald Durrel's childhood, and his Corfu menagerie. He offered a snake to a 'pet' hoopoe and and watched it (the snake) get mangled. I can't remember and I don't know if it was feeding or defensive behaviour, but thanks to that it didn't surprise me when you said hoopoes are related to hornbills.
You omitted two tidbits about the Hoopoe: its modification of uropygial gland in nesting female and chicks which acts as predator deterrent (a sort of avian skunk), and its unusually unsteady flight, which helps it to avoid birds of prey.
Also, ornithologists turned historical descriptions of Northern Bald Ibis from Europe into several other birds, among others Hoopoe, Night Heron and Cormorant.
By the late 1800s, however, most had realised that all three were close relatives
How much serious research was really done on the question of these somewhat obscure* birds' relationships in ye olden days? Didn't consensus on this issue rather emerge in the usual way: by some influential ornithologist(s) of the day publishing some classification scheme that everyone else just happily accepted (because it seemed to 'make sense'), and then happily followed for generations?
* 'Obscure' from the viewpoint of a 19th century European or American naturalist, that is.
Hoopoes and woodhoopoes are similar
I know that they share some subtle osteological characters, but apart from having curved bills, are they really all that similar in appearance, ecology, or behaviour? As your book chapter that-was-not-to-be says, there are plenty of differences between Upupa and woodhoopoes regarding, for example, plumage colouration, locomotion, vocalisations, foraging behaviour, and sociability.
Or, more generally speaking: it would be interesting to know to what extent peoples' perception of these two bird clades' similarities are - subconsciously - influenced by the fact that members of both clades have been given the vernacular name 'hoopoe' in English. (In French, by contrast, hoopoe is huppe while woodhoopoe is irrisor. Would a French-speaker therefore be more likely than an English-speaker to notice and to emphasise superficial differences rather than superficial similarities between woodhoopoes and true hoopoes?)
woodhoopoe mortality seems to be about twice as high as that of other small birds from the same habitats
@ Brian on Comment 5:
Thanks for the clarification, I learned something today. Yes, I've always seen this birds from a distance. They nest very far up in the canopy of very tall trees, usually facing open meadows.
Too bad this book will never see print. It seems like an excellent read. Considering the popularity of bird studies throughout time, it's amazing how the relationships between the various bird families has managed to remain such a controversial hot topic to this day.
Dartian: there have been some studies about the affinities of woodhoopoes in the 19th century. For example, there is this paper by Hugh Strickland from 1843. He used the generic name Irrisor for woodhoopoes (the name Phoeniculus seems to have been overlooked by most authors at that time), and concluded that they are most closely related to hoopoes as both share a unique morphology of the bill, contrary to Lafresnaye who had disputed this. Strickland also notes that woodhoopoes had earlier been placed in several different genera of long-billed birds (Upupa, Merops, Promerops, Epimachus). He wasn't sure where to place the Upupidae, but didn't mention hornbills as possible relatives (although it had already been suggested by Blyth in the 1830s). He apparently didn't convince everyone, but this paper by Murie (1873), who examined the anatomy of both groups, confirmed their relationship and concluded that their closest relatives are the hornbills. Murie's paper also reviews what had previously been said about their relationships.
Obviously, my absence means that I haven't been able to keep up with comments and responses. Some quick responses here (thanks much for comments, hope you liked these articles)...
-- Comment 11: bird at left is a hornbill, used there because accompanying section of text discusses close relationship between hornbills and hoopoes.
-- Comment 13: skunk-like 'stink gland' ability of hoopoes and woodhoopoes is indeed mentioned in article - see paragraph adjacent to pic of Common scimitarbill.
-- Comment 14: I suppose you're right that hoopoes sensu stricto and woodhoopoes are different in general outward appearance, but their close affinity is well established by osteology at least. Both share medially projecting flanges on the ventral part of the coracoid, a peculiar 'hook' on the proximal phalanx of manual digit II, an 'anvil-shaped' stapes and a list of other characters... both groups are also very similar in overall skeletal morphology, sharing limb bone proportions, relatively stout humeri, big retroarticular processes, long hallux etc. Maurer and Raikow have also shown that various muscle characters shared by hoopoes and woodhoopoes aren't seen elsewhere. As for the "woodhoopoe mortality seems to be about twice as high as that of other small birds from the same habitats" quote, it comes from...
Ligon, J. D., Carey, C., & Ligon, S. H. 1988. Cavity roosting, philopatry, and cooperative breeding in the Green Woodhoopoe may reflect a physiological trait. Auk 105, 123-127.
Lars: vielen Dank for those references!
(As a side note, I find the writing style and the expressions used in many 19th century scientific papers pretty awesome. For example, Strickland says that using just a single character - e.g., bill shape - to classify birds is "a vicious arrangement". And Murie, when reviewing upupiform taxonomy, refers to "Huxley's grand Balaclava charge at the birds". Great stuff!)
Strickland [...] concluded that [woodhoopoes] are most closely related to hoopoes
Yes, to a modern reader at least, that certainly seems to be his take-home message. It's notable, however, that Strickland's paper was published in 1843, 16 years before Darwin's Origin of Species*. In other words, at a time when pretty much all naturalists were (or, at least, were supposed to be) de facto creationists. Thus, when Strickland said that two bird taxa were 'related' he probably did not mean that in the same sense that a modern evolutionary biologist would.
* Hugh Strickland died in 1853.
Darren: thank you, too, for the reference! And welcome back!
at a time when pretty much all naturalists were (or, at least, were supposed to be) de facto creationists
What about Lamarckism? ...OK, Lamarckism wouldn't lead to "related", would it.
What about Lamarckism?
Lamarckism was not mainstream; Lamarck didn't have many supporters (especially not outside of France), and his ideas (when they weren't ignored altogether) were rejected and ridiculed by most of his contemporaries*.
* Ironically, much later on, roughly during the time between Darwin's death and the emergence of the Modern Synthesis in the nineteen twenties/thirties, lamarckian ideas about the evolutionary process were quite widespread among biologists and paleontologists. (And in the Soviet Union and elsewhere in the Eastern Bloc, lamarckism was the official evolutionary doctrine until even later than that. But that's another story.)
Thus, when Strickland said that two bird taxa were 'related' he probably did not mean that in the same sense that a modern evolutionary biologist would.
Wasn't Strickland a quinarian? In which case, he probably wouldn't have meant 'related' in the sense that anyone not used to thinking at right angles to reality would have.
Dartian: At least Owen, who was very influential, did believe in some form of (non-Darwinian) evolution, although I think he never wrote much about the details of how he thought it worked. I don't think Strickland was an evolutionist, but he envisioned relationships between different organisms as a kind of irregular map or network of interconnected taxa. In this context, his statement about Upupidae being related in three different directions to Alcedinidae, Paradisaeidae, and Corvidae makes sense. His statement that the resemblance between Upupa and what we now call Furnariidae "seems to be one of analogy only" seems to mean that he didn't think of them as being directly connected. There is a part of his diagram reproduced here(p. 170). So Strickland was not a quinarian, and he actually was one of the leading opponents of quinarianism. Here is a biography of him, and a collection of his papers. His paper "On the true method of discovering the natural system in botany and zoology" (p. 408-417) explains his idea of classification, and ends with a long list of things that Swainson's quinarian bird classification got wrong.
By the way, Strickland is sometimes said to be the first person in history to be run over by a train (he was examining the geology), but according to wikipedia this is incorrect. He also was the first to publish the idea that the dodo is a pigeon.
Wasn't Strickland a quinarian?
Lars beat me to it; Strickland was, in fact, a leading critic of the quinarians.
To what Lars wrote may be added that Alfred Russel Wallace was a supporter of Strickland's classification principles already before he co-discovered natural selection, and that Wallace later had no trouble in reconciling these principles with his evolutionary thinking.
Strickland is sometimes said to be the first person in history to be run over by a train
That was when Strickland became 'Struckland'.