Overview

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The native New Guinean Pitohui is the first documented bird species that contains a potentially poisonous chemical defense- batrachotoxin (Weldon 2000). Ranging from 65-100g in mass and 23cm in length, these omnivorous birds are easily distinguishable by their coloration and plumage patterns (Dumbacher et al. 2008, Dumbacher et al. 2000). Five of the six known species have a red/orange coloration on their breast and back and are black/brown on the head, wings and tail (Tidwell 2001). The sixth species, however, has a white coloration on the breast and back. Although little is known about their reproduction, their nests are generally 2-3m off the ground and it is suggested that they are cooperative breeders (Dumbacher 1999, Ben-Ari 2000, Dumbacher et al. 2000). Unlike other birds, Pitohui are very sociable and travel in mixed species flocks (Dumbacher et al. 2000).

Due to the toxicity of these birds, New Guinean tribal natives consider them both poisonous and inedible, as the toxin’s effects are orally numbing and allergy-like (Weldon and Rappole 1997, Weldon 2000, Dumbacher et al. 2000). This response is caused by neurotoxic steroidal alkaloids, which effectively disrupt voltage-gated sodium channels (Dumbacher et al. 2000, Jonsson et al. 2008). These neurotoxic alkaloids are obtained by the ingestion of meylrid beetles, a common Pitohui dietary item, and are then secreted by the uropygial gland and smeared onto the feathers and skin (Dumbacher et al. 2004, Hagelin and Jones 2007, Weldon 2000, Dumbacher et al. 2000). While the toxicity has been found to vary with each species, it is assumed that the batrachotoxin functions as an anti-predation repellent to both vertebrates and invertebrates, specifically ectoparasites (Jønsson et al. 2008). The two most toxic species are speculated to exhibit aposematism as they are also the most brightly colored (Dumbacher and Fleischer 2001).

Ben-Ari E.T., 2000. Birds of a (toxic) feather. Bioscience 50: 1136.

Dumbacher J.P. 1999. Evolution of toxicity in pitohuis: I. effects of homobatrachotoxin on chewing lice (order Phthiraptera). The Auk 116: 957-963.

Drumbacher J.P., K. Deiner, L. Thompson, R.C. Fleischer. 2008. Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds. Molecular Phylogenetics and Evolution 49:774-781.

Drumbacher J.P., R.C. Fleischer. 2001. Phylogenetic evidence for colour pattern convergence in toxic pitohuis: Müllerian mimicry in birds?. Proceedings of the Royal Society B 268: 1971-1976.

Dumbacher J.P., T.F.Spande, J.W. Daly. 2000. Batrachotoxin alkaloids from passerine birds: a second toxic bird genus (Ifrita kowaldi) from New Guinea. Proceedings of the National Academy of Sciences 97: 12970-12975.

Drumbacher J.P., A. Wako, S.R. Derrickson, A. Samuelson, T.F. Spande, J.W. Daly. 2004. Melyrid beetles (Choresine): a putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. Proceedings of the National Academy of Sciences 101: 15857-15860.

Hagelin J.C., I.L. Jones. 2007. Bird odors and other chemical substances: a defense mechanism or overlooked mode of intraspecific communication. The Auk 124:741-761.

Jønsson K.A., R.C.K. Bowie, J.A. Norman, L. Christidis, J. Fjeldså. 2008. Polyphyletic origin of toxic Pitohui birds suggests widespread occurrence of toxicity in corvoid birds. Biology Letters 4: 71-74.

Weldon P.J. 2000. Avian chemical defense: toxic birds not of a feather. Proceedings of the National Academy of Sciences 97: 12948-12949.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records: 25
Specimens with Sequences: 7
Specimens with Barcodes: 7
Species: 4
Species With Barcodes: 2
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Wikipedia

Pitohui

The pitohuis are birds endemic to New Guinea. All six species were formerly classified in the Pitohui genus, classified in the same family. Two species are now classified in the Oriolidae, and three species in the Pachycephalidae (there is one species incertae sedis).

Most taxonomists now separate the species as follows:

Oriolidae[edit]

Pachycephalidae[edit]

Incertae sedis[edit]

They are brightly coloured, omnivorous birds. The skin and feathers of some pitohuis, especially the variable and hooded pitohuis, contain powerful neurotoxic alkaloids of the batrachotoxin group (also secreted by the Colombian poison dart frogs, genus Phyllobates). These are believed to serve the birds as a chemical defence, either against ectoparasites or against visually guided predators such as snakes, raptors or humans.[1] The birds probably do not produce batrachotoxin themselves. The toxins most likely come from the beetle genus Choresine, part of the birds' diets.[2] Due to their toxicity, Papua New Guineans call the pitohuis rubbish birds as they are not good for eating; in desperate times, though, they can be consumed but only after the feathers and skin are removed and the flesh is coated in charcoal and then roasted. (Piper, 2007)

The hooded pitohui is brightly coloured, with a brick red belly and a jet-black head. The variable pitohui, as its name implies, exists in many different forms, and 20 subspecies with different plumage patterns have been named. Two of them, however, closely resemble the hooded pitohui.

The birds' bright colours are suggested to be an example of aposematism (warning colouration), and the similarity of the hooded pitohui and some forms of the variable pitohui might then be an example of Müllerian mimicry, in which dangerous species gain a mutual advantage by sharing colouration, so an encounter with either species trains a predator to avoid both.[3]

See also[edit]

References[edit]

  1. ^ (Dumbacher, et al., 1992)
  2. ^ (Dumbacher, et al., 2004).
  3. ^ (Dumbacher & Fleischer, 2001)
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