Hooded pitohui
Hooded pitohui | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Oriolidae |
Genus: | Pitohui |
Species: | P. dichrous
|
Binomial name | |
Pitohui dichrous (Bonaparte, 1850)
| |
Synonyms | |
Rectes dichrous (Bonaparte, 1850) |
The hooded pitohui (Pitohui dichrous) is a species of bird in the genus Pitohui found in New Guinea. It was long thought to be a whistler (Pachycephalidae) but is now known to be in the Old World oriole family (Oriolidae). Within the oriole family, this species is most closely related to the variable pitohuis in the genus Pitohui, and then the figbirds.
A medium-sized songbird with reddish-brown and black plumage, this species is one of the few known poisonous birds, containing a range of batrachotoxin compounds in its skin, feathers and other tissues. These toxins are thought to be derived from their diet and may function both to deter predators and to protect the bird from parasites. The close resemblance of this species to other unrelated birds also known as pitohuis which are also poisonous is an example of convergent evolution and Müllerian mimicry. Their appearance is also mimicked by unrelated non-poisonous species, a phenomenon known as Batesian mimicry. The toxic nature of this bird is well known to local hunters, who avoid it. It is one of the most poisonous species of pitohui, but the toxicity of individual birds can vary geographically.
The hooded pitohui is found in forests from sea level up to 2,000 m (6,600 ft) but is most common in hills and low mountains. A social bird, it lives in family groups and frequently joins and even leads
Taxonomy and systematics
The hooded pitohui (Pitohui dichrous)[2] was described by the French ornithologist Charles Lucien Bonaparte in 1850.[3] Bonaparte placed it in the genus Rectes which had been erected in the same year by Ludwig Reichenbach as an alternative name for the genus Pitohui, which had been described by René Lesson in 1831. No explanation was given for the preference of the newer name over the established older one, but it was common to prefer Latin names over non-Latin names, and to provide Latin names to those without.[4] Richard Bowdler Sharpe encapsulated that attitude when he wrote in 1903 "Pitohui is doubtless an older name than Rectes, but can surely be laid aside as a barbarous word".[5][6] Eventually however the principle of priority, which favours the first formal name given to a taxon, was applied, and Rectes was suppressed as the junior synonym of Pitohui.[4]
The hooded pitohui was placed in the genus
The hooded pitohui is
Pitohui, the common name for the group and the genus name, is a Papuan term for rubbish bird, a reference to its inedibility.[11] The specific name dichrous is from the Ancient Greek word dikhrous, meaning 'two coloured'.[12] Alternate names for the hooded pitohui include the black-headed pitohui[13] and lesser pitohui.[14]
Physiology and description
The hooded pitohui is 22 to 23 cm (8.7–9.1 in) long and weighs 65–76 g (2.3–2.7 oz). The adult has a black upperwing, head, chin, throat and upper breast and a black tail. The rest of the plumage is a reddish brown. The bill and legs are black, and the irises are either reddish brown, dark brown or black. Both sexes look alike. Juvenile birds look like adults, except that the rectrices of the tail and remiges of the wing are tinged with brown.[10]
Toxicity
In 1990 scientists preparing the
Bioassays of their tissue found that the skins and feathers were the most toxic, the heart and liver less toxic, and the skeletal muscles the least toxic parts of the birds.[17] Of the feathers, the toxin is most prevalent in those covering the breast and belly.[19] Microscopy has shown that the toxins are sequestered in the skin in organelles analogous to lamellar bodies and are secreted into the feathers.[20] The presence of the toxins in muscle, heart and liver shows that hooded pitohuis have a form of insensitivity to batrachotoxins.[17] A 65 g (2.3 oz) bird has been estimated to have up to 20 μg of toxins in its skin and up to 3 μg in its feathers.[15] This can vary dramatically geographically and by individual, and some have been collected with no detectable toxins.[19]
The poisonous pitohuis, including the hooded pitohui, are not thought to create the toxic compound themselves but instead sequester them from their diet. Phyllobates frogs kept in captivity do not develop the toxins, and the extent of the toxicity varies both in the pitohuis across their range and also across the range of the unrelated blue-capped ifrit, another New Guinean bird found with toxic skin and feathers. Both of these facts suggest that the toxins are obtained from the diet.[19] The presence of the toxins in the internal organs as well as the skins and feathers rules out the possibility that the toxins are applied topically from an unknown source by the birds.[17]
One possible source has been identified in the forests of New Guinea: beetles of the genus Choresine (family Melyridae), which contain the toxin and have been found in the stomachs of hooded pitohui. An alternative explanation, that the birds and beetles both get the toxin from a third source, is considered unlikely as the blue-capped ifrit is almost exclusively insectivorous.[18]
Ecology
The function of the toxins to the hooded pitohui has been the source of debate and research since its discovery. The initial suggestion was that the toxins acted as a chemical deterrent to predators.[15] Some researchers cautioned this suggestion was premature,[21] and others noted that the levels of batrachotoxins were three orders of magnitude lower than in the poison dart frogs that do use it in this way.[22]
Another explanation for the purpose of the toxins is to mitigate the effects of parasites.
A number of authors have noted that the two explanations, as a chemical defence against predators and as a chemical defence against ectoparasites, are not mutually exclusive, and evidence for both explanations exists.[16][24] The fact that the highest concentrations of toxins are bound in the feathers of the breast and belly, in both pitohuis and ifrits, has caused scientists to suggest that the toxins rub off on eggs and nestlings providing protection against predators and nest parasites.[19]
One argument in favour of the toxin acting as a defence against predators is the apparent
There have also been experiments to test pitohui batrachotoxins on potential predators. They have been shown to irritate the buccal membranes of brown tree snakes and green tree pythons, both of which are avian predators in New Guinea. The unpalatability of the species is also known to local hunters, who otherwise hunt songbirds of the same size.[17]
The existence of resistance to batrachotoxins and the use of those toxins as chemical defences by several bird families have led to competing theories as to its evolutionary history. Jønsson (2008) suggested that it was an ancestral adaptation in Corvoidea songbirds, and that further studies would reveal more toxic birds.[8] Dumbacher (2008) argued instead that it was an example of convergent evolution.[27]
Distribution and habitat
The hooded pitohui is
Behaviour
Calls
The hooded pitohui makes a variety of
Diet and feeding
The diet of the hooded pitohui is dominated by fruit, particularly figs of the genus
Breeding
Little is known about the breeding biology of the hooded pitohui and its relatives due to the difficulties of studying the species high in the canopy of New Guinea.[30] Nests with eggs of the hooded pitohui have been found from October through to February.[10] The nest that has been described was 2 m (7 ft) off the ground. The nest is a cup of vine tendrils, lined with finer vines and suspended on thin branches.[10][30]
The
Relationship with humans
The toxic and unpalatable nature of the hooded pitohui has long been known to local people in New Guinea, and this knowledge has been recorded by Western scientists as far back as 1895.[34] In spite of this, and reports of toxicity in birds going back to classic antiquity, before the discovery that the hooded pitohui was toxic, toxicity was not a trait that scientists attributed to birds. The discovery of toxicity in birds, triggered by this species, sparked interest in the subject and a re-examination of older accounts of unpalatability and toxicity in birds, although the field is still understudied.[16]
Status and conservation
Common and widespread throughout New Guinea, the hooded pitohui is evaluated as a
Notes and references
- ^ Since then the variable pitohui has been split into three species:
- Northern variable pitohui (Pitohui kirhocephalus)
- Raja Ampat pitohui (Pitohui cerviniventris)
- Southern variable pitohui (Pitohui uropygialis)[2]
- ^ Or four, if the shrikethrushes are treated as a separate family, Colluricinclidae, from the whistlers.[4]
- ^ . Retrieved 19 November 2021.
- ^ a b Gill, F.; Donsker, D., eds. (2017). "Orioles, drongos & fantails". IOC World Bird List (v 7.2). Retrieved 10 June 2017.
- ^ Bonaparte, Charles Lucien (1850). "Note sur plusieurs familles naturelles d'oiseaux, et descriptions d'espèces nouvelles". Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences (in French). 31: 561–564 [563].
- ^ a b c d Dumbacher, J. P. (2014). "A taxonomic revision of the genus Pitohui Lesson, 1831 (Oriolidae), with historical notes on names" (PDF). Bulletin of the British Ornithologists' Club. 134 (1): 19–22.
- ^ Sharpe, Richard Bowdler (1903). A Hand-List of the Genera and Species of Birds: Volume 4. Vol. 4. London: Trustees of the British Museum. p. 267.
- ^ Quoted in Dumbacher (2014), p. 20
- ISBN 978-84-96553-42-2.
- ^ PMID 18055416.
- .
- ^ S2CID 216419243. Retrieved 2 June 2017.
- ^ Jobling, J. (2017). "Key to Scientific Names in Ornithology: Pitohui". Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. Retrieved 14 June 2017.
- ^ Jobling, J. (2017). "Key to Scientific Names in Ornithology: dikhrous ". Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. Retrieved 7 June 2017.
- JSTOR 1367895.
- ^ "Pitohui dichrous - Avibase". avibase.bsc-eoc.org. Retrieved 2017-06-03.
- ^ PMID 1439786.
- ^ PMID 25839151.
- ^ S2CID 40669290.
- ^ PMID 15520388.
- ^ PMID 11035772.
- PMID 24617754.
- S2CID 206631249.
- ^ .
- JSTOR 4089675.
- ^ JSTOR 3546161.
- S2CID 19317909.
- PMID 11571042.
- ^ PMID 18929671.
- .
- PMID 28276508.
- ^ .
- .
- ^ Parker, S.A. (1962). "Notes on some undescribed eggs from New Guinea". Bulletin of the British Ornithologists' Club. 82: 132–133.
- hdl:2246/833.
- JSTOR 2452783.
- hdl:2263/2499.