Evidence of social intelligence and playfulness in not-particularly-brainy parrot-like birds
(writing in progress)
Look at the playful and socially intelligent behaviour in the following two video clips of the largest and rarest of the Indonesian corellas, namely Cacatua moluccensis.
In the first (https://www.youtube.com/watch?v=HHIENaZXWTY):
This individual is laughing like a human, and playing antics as if to clown around to give its humans something really to laugh about.
I do not doubt that this bird ‘means it’ as opposed to merely performing mimicry with no understanding of what it is expressing.
The second (https://www.youtube.com/watch?v=jzOJoLVkSTE) shows the same species dancing to music on the floor. This indicates both its semi-terrestriality (which it shares with all other corellas and various other related genera, including Eolophus and Nymphicus) and - again - its playfulness and social intelligence.
According to my calculations:
This species, Cacatua moluccensis, has a braininess score of 6/10 relative to all other psittaciforms on Earth. This means that this exceptionally entertaining, comical species, with a sense of humour and an extreme desire to play with humans in the case of many individuals kept in captivity, is not particularly brainy for a parrot-like bird.
Lophochroa leadbeateri (https://www.inaturalist.org/taxa/145357-Lophochroa-leadbeateri) is possibly the most beautiful of all cockatoos, and the only one penetrating the nutrient-poorest parts of the Australian interior.
This species has a braininess score of 4/10 for a parrot-like bird. This is 'below par'. Although L. leadbeateri is brainy among birds in general, it is less brainy than expected for a psittaciform (https://en.wikipedia.org/wiki/Parrot).
Cactus moluccensis is brainer than Lophochroa leadbeateri. However, the difference in captive behaviour is not fully explained by encephalisation, and presumably reflects social adaptations as well in the different habitats of the two species.
Cacatua moluccensis is a bird of rainforest on a few Indonesian islands, now virtually extinct in the wild. Lophochroa leadbeateri is a bird of the extremely nutrient-poor, drought-prone outback of Australia.
My point is this:
Those parrot-like birds that behave in a way most engaging for their human ‘keepers’ are not the brainiest of a brainy lineage; it is just that their social nature predisposes them to complex interaction, which can be projected intelligently and with versatility on to humans if the bird so wishes.
Can readers imagine the intelligence in a species such as the palm cockatoo (Probosciger aterrimus), which scores closer to 10/10 among the psittaciforms of the world, but is not particularly social and so does not have a comparable reputation as a captive species?
The various species of cockatoos have a wide range of encephalisation among parrot-like birds. However, even the least encephalised spp. of cockatoos are so socially intelligent that it can surprise the naive.
In the case of L. leadbeateri, there is a combination of intelligence (which I would equate with cognitive empathy) and delicate colouration. An ornate crest is not something that I think most naturalists would expect from a habitat as unpromising as the real habitat of this species: the interior of Australia where it is not only semi-arid and drought-prone but nutrient-poorer than any climatically similar region on Earth.
Please bear in mind, L. leadbeateri is not nearly as entertaining and interactive as the C. moluccensis shown in the video clips above; but it is still remarkable for a bird evolved in such inauspicious circumstances, not so?
If there is a distinction between 'social intelligence' and other forms of intelligence is, this has not been studied enough to measure it.
When it comes to comparing say dolphins, elephants, parrots, and humans in terms of social intelligence, and then quantifying their social intelligence relative to their other aspects of intelligence, one can imagine this keeping scientists busy for centuries.
What I am doing here is mainly conceptualisation, and a kind of preliminary assessment based on the most obvious evidence.
To pinpoint a particular puzzle:
The glossy cockatoo (see my recent Posts) seems to show exceptional social intelligence towards humans when hand-reared by humans. But it is far from clear to me why it evolved such social intelligence, given its remarkably simple trophic niche and its only modest sociality within its own species.
If a species can have modest overall intelligence but exceptionally well-developed social intelligence, the budgerigar (Melopsittacus undulatus, https://www.inaturalist.org/taxa/19339-Melopsittacus-undulatus) exemplifies this. This species is brainy for a bird, but not more so than average brainy for a psittaciform – and yet is exceptionally rewarding as a pet.
On the other hand, a species can have extreme overall intelligence, and yet have little social intelligence when it comes to interacting with humans.
Baboons exemplify this. They are brainy by any standards, but are useless as pets; they just cannot relate to humans in the way parrot-like birds can.
After correcting for systematic differences between birds and mammals in brain size and structure, we can see that the budgerigar is no match in encephalisation for any baboon. This is because its brain is not as large, relative to body size after allometric and bird-mammal correction, as that of baboons. In the overall scheme of things, baboons are ‘smarter’ than the budgie (although both are smart relative to birds and mammals generally).
Baboons are exceptionally smart among primates whereas the budgerigar is not exceptionally smart for a psittaciform.
And yet there is no comparison in the social intelligence from a human perspective: the budgie is a joy to keep, and can even converse in a rudimentary way with its human keeper in human language. By contrast, baboons can hardly get on with a human keeper enough to make a nominal pet – even if the monkey has been lovingly hand-reared by suckling at a human breast.
One way in which this can be expressed:
The brain of the budgerigar represents 10 units of intelligence overall, whereas that of the baboon represents 15 units of intelligence overall. However, the brain matter devoted to the kind of social intelligence that makes for good relationship with a human represents is say 3 units of intelligence in the budgerigar, versus only 1 unit of intelligence in the baboon.
What this works out to is that this kind of social intelligence contributes 3/10 of overall intelligence in the budgerigar, but only 1/15 of overall intelligence in the baboon.
In the final analysis, the budgerigar seems to be threefold more intelligent than the baboon in social interactions with a human keeper, despite seeming to have only two-thirds the overall intelligence.
(writing in progress)
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Clarifying braininess in the desert-dwelling cockatoo, Lophochroa leadbeateri mollis:
The encephalisation score for Lophochroa leadbeateri, the only cockatoo that comes close to inhabiting hummock grassland, is 4/10. This is derived from a data set for all psittaciform birds worldwide. This species is thus less than average in braininess for a parrot-like bird.
To put this into context:
Lophocroa leadbeater does seem less brainy than that best-known of intelligent parrots, the African grey parrot (Psittacus erithacus). The former has body mass 460 g and brain size 8.5 ml, whereas the latter has body mass 406 g and brain size 9.2 ml. This means that the African grey parrot is considerably smaller in body size but has the larger brain.
However, another genus of parrots extremely familiar in aviaries, Amazona from tropical South America, is somewhat less brainy than L. leadbeateri.
Given that Lophochroa leadbeateri has a braininess score of 4/10 for a parrot-like bird, how do its closest relatives (particularly belonging to genera Cacatua and Eolophus) compare?
Well, sharing a score of 4/10 are the Philippine corella Cacatua haematuropygia (which actually has the same absolute body mass and brain size as L. leadbeateri), the western corella Cacatua pastinator (indigenous to Perth but now only found elsewhere in southwestern Australia), the cockatiel Nymphicus hollandicus, and the galah Eolophus roseicapillus. The long-billed corella Cacatua tenuirostris (originally centred on the treeless grasslands on basalt in western Victoria) scores 4.5/10, as does the budgerigar Melopsittacus undulatus. These spp. are all less than average in braininess for parrot-like birds worldwide.
By contrast, several other spp. of Cacatua are brainier than the average psittaciform bird worldwide: these include the Indonesian Cacatua sulphurea (probably 6/10), the Indonesian Cacatua alba (7/10), the Indonesian Cacatua moluccensis (6/10), and the Australian and New Guinean Cacatua galerita (6/10).
So L. leadbeateri is indeed not particularly brainy for a parrot-like bird, a cockatoo, or a relative of corellas. It is slightly less brainy than the budgerigar, and about as brainy as the cockatiel. The latter is an aberrantly small-bodied cockatoo, and one of the most popular of pets besides the budgerigar. On the other hand, L. leadbeateri is certainly brainy enough to be an endearing and behaviourally complex pet, provided it decides to like its human keeper.
Overall, the results in terms of encephalisation are rather ambivalent. I would not rely on this aspect in explanation of the ecological niche of L. leadbeateri as one of the few cockatoos which extends into habitat combining semi-aridity and extreme nutrient-poverty.
Please see https://www.youtube.com/watch?v=xPg2pJZjQs4.
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