New intelligence on Australasian parrots

Everyone knows that parrots (order Psittaciformes, https://en.wikipedia.org/wiki/Parrot) are among the brainiest of birds. However, how many realise that Australia is endowed with both the brainiest and the least brainy of parrots?

Braininess is measured by the mass of the brain relative to the mass of the whole body, corrected mathematically according to the principles of allometry (https://shoonem.ch/papers/40.pdf and https://www.researchgate.net/publication/8248943_Interspecific_Allometry_of_the_Brain_and_Brain_Regions_in_Parrots_Psittaciformes_Comparisons_with_Other_Birds_and_Primates).

I did my own analysis of the data, to produce a score from 1 to 10 for each species of parrot relative to all the other parrots in the world. (Please see the first comment below.)

This is what I found.

The brainiest of all parrots seems to be Probosciger aterrimus (https://en.wikipedia.org/wiki/Palm_cockatoo). It scores 10 out of 10 and could be the brainiest bird on Earth.

Tying for least brainy of parrots - some of which score only 1 out of 10 - are various species specialised for a terrestrial way of life.

Both of these extremes occur in Australasia, including within the country of Australia itself.

Probosciger aterrimus is the largest-bodied of all cockatoos. It lives in rainforest in New Guinea and far-northern Queensland, and extracts the seeds of palms and other trees from their hard coverings.

Whereas parrots typically have a beak functioning like a pair of secateurs, the beak of P. aterrimus is different: it cannot be closed, and seems particularly dexterous. The combination of dexterous feet (shared with other cockatoos) and this extreme beak allows for a complex manipulation of objects (e.g. see https://www.inaturalist.org/observations/89171671 and https://www.inaturalist.org/observations/86121905 and https://www.inaturalist.org/observations/84355115).

Remarkably, Probosciger aterrimus is capable of making and playing musical instruments (https://www.youtube.com/watch?v=_cfYezXDyAA and https://www.youtube.com/watch?v=2MIoXh_ORMw and https://www.youtube.com/watch?v=2_wh3liNT_o and https://www.youtube.com/watch?v=xvzeKCq5nvg).

Worldwide, P. aterrimus is the largest-bodied parrot that lives in a primate-free rainforest, hinting that its braininess may have something to do with its occupation of a primate-like niche. Is it not the closest animal in terms of intelligence - and perhaps also ecologically - to a monkey in Australasia?

The least brainy of all parrots worldwide are Australian species that forage mainly on the ground and mainly at dawn and dusk, in dry or coastal areas: Pezoporus spp. (https://en.wikipedia.org/wiki/Pezoporus), Neopsephotus bourkii (https://en.wikipedia.org/wiki/Bourke%27s_parrot), and several species of Neophema (https://en.wikipedia.org/wiki/Neophema) and Psephotus (https://en.wikipedia.org/wiki/Red-rumped_parrot). These inconspicuous species probably include the widespread but vanishingly rare Pezoporus occidentalis (https://en.wikipedia.org/wiki/Night_parrot), the brain of which has yet to be measured.

The terrestrial species of parrots fill in for mammals other than monkeys on these isolated landmasses. The Australian species eat mainly seeds and retain strong flight, giving them an advantage over rodents in a land of fire, drought and flood. And in New Zealand, a large terrestrial parrot (Strigops habroptilus, https://en.wikipedia.org/wiki/K%C4%81k%C4%81p%C5%8D) is herbivorous and flightless.

The niches of terrestrial parrots do not seem to demand particular mental capacities, particularly in view of the relative freedom from predation on islands. However, these are the parrots now most threatened with extinction, given the advent of introduced predators such as Vulpes and Felis.

Focussing on the country of Australia itself, here is a concise ranking of parrots in order of decreasing braininess on my scale of 1-10:

Parrots on other continents are not as ecologically diversified as those in Australasia. However, they do vary in braininess to some degree.

The brainiest species beyond Australasia are certain Arini (https://en.wikipedia.org/wiki/Macaw) and species in other genera (https://en.wikipedia.org/wiki/Conure) in South America, and Psittacus erithacus (https://en.wikipedia.org/wiki/Grey_parrot) in Africa. These score 7-8, equivalent to certain species of cockatoos of Australia and the Moluccas in nearby Indonesia (https://en.wikipedia.org/wiki/Salmon-crested_cockatoo). The resemblance extends to vocal abilities and occasional use of tools.

The least brainy beyond Australasia are Psilopsiagon (https://en.wikipedia.org/wiki/Psilopsiagon) and Coracopsis (https://en.wikipedia.org/wiki/Vasa_parrot). The former species are restricted to the Andes, where they live above the treeline and forage in shrubs. The latter live on islands in the Indian Ocean, where they evolved in relative exemption from predation.

Among the Arini of central and South America we find the following reminder that braininess varies considerably among habitats and within clades.

Cyanopsitta spixii (https://en.wikipedia.org/wiki/Spix%27s_macaw) scores only 4, which is in line with certain Australasian parrots of similar body size such as Eclectus roratus (https://en.wikipedia.org/wiki/Eclectus_parrot). Its braininess is thus below average for a macaw and for a parrot, and it has become extinct in the wild. The specialised habitat of C. spixii in riverine woodlands may have provided predictable resources, requiring limited behavioural versatility.

A particular puzzle is that there are few if any counterparts on other continents for various small-bodied parrots of Australasia (including New Guinea and nearby Indonesia), which score 7-8: Oreopsittacus arfaki (https://en.wikipedia.org/wiki/Plum-faced_lorikeet#:~:text=The%20plum%2Dfaced%20lorikeet%20is,female%20has%20a%20green%20forehead.), Neopsittacus pullicauda (https://en.wikipedia.org/wiki/Orange-billed_lorikeet#:~:text=The%20orange%2Dbilled%20lorikeet%20(Neopsittacus,yellowish%20streaking%20on%20the%20head.), and Micropsitta spp.(https://en.wikipedia.org/wiki/Pygmy_parrot).

Although these are all tree-dwelling, and they include the only birds on Earth that eat lichens and fungi as staples, too little is known about their ways of life to explain their combination of braininess and small body size.

Publicado por milewski milewski, 29 de diciembre de 2021

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HOW I SCORED BRAININESS:

Braininess is a measure of the size of the brain relative to the size of the body. This relationship is mathematically scaled in view of the tendency for small-bodied birds to have proportionately larger brains than those of big birds.

I plotted the brain volume vs body mass of parrots using a dataset compiled by neuroscientist Andrew Iwaniuk (available on the web).

The volume of the brain is directly proportionate to the mass of the brain (https://cdnsciencepub.com/doi/abs/10.1139/z01-204). Researchers determine brain size by filling the endocranial cavity of a skull with lead shot, decanting it, and measuring the volume in this indirect way.

In each species, an average is calculated based on as many specimens as possible.

I converted information about how much each species deviated from the 'norm' predicted for its body size to a score from 1 to 10.

This means an assumption that the 'norm' (= expected braininess) for parrots in general is 5.

Please note that this ranking does not mean that the brain of a species scoring 10 is tenfold more massive/voluminous than that of a species scoring 1. The value is relative, but not in that way.

For some species, the scores were based on only one or a few specimens, so they may change in future when more measurements become available.

Publicado por milewski hace 5 meses (Marca)

The heathland inhabited by Pezoporus flaviventris is similar to that found on similar nutrient-poor sandy soils in South Africa. A component of particular interest in both cases is the Restionaceae (https://en.wikipedia.org/wiki/Restionaceae). The seeds of these sclerophyllous graminoid plants are eaten by P. wallicus in Australia (see https://www.inaturalist.org/observations/62763799 and https://www.inaturalist.org/observations/8067129 and https://www.inaturalist.org/observations/68486771 and https://www.inaturalist.org/observations/69969381) and rodents such as Acomys subspinosus (https://en.wikipedia.org/wiki/Cape_spiny_mouse and http://cameratrap.mywild.co.za/2013/11/spiky-mice.html and https://www.ewt.org.za/wp-content/uploads/2019/02/2.-Cape-Spiny-Mouse-Acomys-subspinosus_LC.pdf) in South Africa. The bird is surely more mobile than the mammal but is it also more intelligent? And if so, what is the ecological advantage?

Publicado por milewski hace 5 meses (Marca)

In the metropolitan area of Perth, Western Australia, there are several indigenous and introduced species of parrots. Zanda latirostris scores 7 in braininess, whereas all the others score less than 5, e.g. Calyptorhynchus banksii naso, Cacatua (Licmetis) tenuirostris, Eolophus roseicapilla, Trichoglossus moluccanus, and Barnardius zonarius semitorquatus.

Publicado por milewski hace 5 meses (Marca)

Thanks for sharing this piece. Very interesting.
Regards,
Mehd

Publicado por mehdh hace 5 meses (Marca)

@mehd Hi Mehd, You are most welcome and I wish you well in your work on the conservation of parrots, with regards from Antoni.

Publicado por milewski hace 5 meses (Marca)

Thank you for sharing!

Publicado por eldirko hace 5 meses (Marca)

@eldirko You're most welcome.

Publicado por milewski hace 5 meses (Marca)

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