Why is the glossy cockatoo so brainy? part 1

The glossy cockatoo (Calyptorhynchus lathami, https://www.inaturalist.org/taxa/116846-Calyptorhynchus-lathami) is exceptionally brainy for an Australian cockatoo.

This is true notwithstanding the fact that the largest species of cockatoo, namely the palm cockatoo (Probosciger aterrimus, https://www.inaturalist.org/taxa/117073-Probosciger-aterrimus), is even brainier.

In encephalisation, the glossy cockatoo scores about 7-7.5/10 relative to the psittaciform birds of the world.

For comparison, other relevant parrot-like birds score as follows:

• palm cockatoo 9.5-10/10 (https://www.researchgate.net/publication/8248943_Interspecific_Allometry_of_the_Brain_and_Brain_Regions_in_Parrots_Psittaciformes_Comparisons_with_Other_Birds_and_Primates),
• Lophochroa leadbeateri only 4/10,
• a corella from the Philippines, namely Cacatua haematuropygia, 4/10,
• Cacatua tenuirostris 4.5/10,
• Cacatua pastinator 4/10,
• Cacatua alba 7/10,
• Cacatua moluccensis 6/10, and
• Cacatua galerita 6.5/10.

Within the same genus as the glossy cockatoo: Calypthorhynchus banksii scores only 4/10; and the complex of cockatoos congeneric with the glossy cockatoo, consisting of C. baudini, C. latirostris and C. funereus, 6.5-7.5/10.
 
The above shows that the glossy cockatoo, which specialises on a diet of casuarina seeds, is indeed brainy even relative to the average psittaciform species worldwide. This helps to explain why it is so valued by aviarists. However, it is by no means as brainy as the palm cockatoo, which

• occurs farther to the north,
• is a far larger bird, and
• is associated with rainforest and a diet of large seeds, without clear specialisation as to taxon of plant.

It is surprising to find such braininess in the glossy cockatoo. This is because there is so little about this species that would lead us to expect it to be particularly intelligent for a bird or for a cockatoo.

The glossy cockatoo has an extremely monotonous diet, and is not particularly gregarious. Furthermore, even its displays and vocalisations seem rather rudimentary.

For example, it is the only cockatoo that virtually lacks the head-crest, an erectile structure characteristic of the whole family Cacatuidae, and useful in communication.

The glossy cockatoo is also far quieter than other cockatoos. (Please bear in mind that the palm cockatoo is famous for being the only species of bird, worldwide, known to make, store, and use musical instruments, https://www.science.org/doi/10.1126/sciadv.1602399#:~:text=The%20only%20reported%20nonhuman%20example,1A%2C%20fig..)

Most cockatoos shriek/scream, or make other shrill and loud noises. However, the only vocalisation that I have heard of in the glossy cockatoo is a soft croaking sound. This vocalisation can be heard in the following video-clip: https://www.youtube.com/watch?v=q73W5IqyD7U .
 
Casuarinas (https://www.inaturalist.org/observations?place_id=any&taxon_id=62890&view=species) are among the dullest trees and shrubs to look at: grey-green or olive-green, dry-looking, always leafless, and in some species diallagous (i.e. going brown in the sense of resurrection plants). Their cones, which are the sole source of food for the glossy cockatoo, are small and dull-looking (https://vicflora.rbg.vic.gov.au/flora/taxon/3eb9d1fd-7808-4734-8091-c0a83203c608). The seeds are small compared with pine seeds (https://www.fdacs.gov/Agriculture-Industry/Pests-and-Diseases/Plant-Pests-and-Diseases/Noxious-Weeds/Casuarina-spp.-Australian-Pines).

The glossy cockatoo itself is often overlooked while it forages in the casuarinas (https://www.youtube.com/watch?v=eZFUBAwkZ20). This is because it is sombre in colouration (apart from the red vanes in the tail, conspicuous when the tail is spread, https://www.inaturalist.org/observations/124525086), and it tends not to vocalise. When it does vocalise, it does so softly.

The best way to find the glossy cockatoo is to look for the freshly-discarded remains of casuarina cones on the ground under the trees. Then listen for the soft but tell-tale clicking sound as the birds break open the cones with their beaks.

This bird has been described as an ‘eating machine’. This is because its foraging mode is so simple, and it has to keep it up for hours to fill the stomachs on these meagre seeds (https://www.youtube.com/watch?v=NAB1v1gDwzg).
 
Do readers see that there is nothing in this scenario that would lead us to expect particular intelligence in this bird?

Even if I were told that the main specialist on casuarina seeds was a psittaciform (https://en.wikipedia.org/wiki/Parrot), I would predict that it would be among the least encephalised of the arboreal parrot-like birds.

But instead we have, in the glossy cockatoo, what has been described as ‘the dolphin of the bird world’ – an exceptionally intelligent species, as revealed when it is hand-reared and kept as a ‘pet’ (https://birdscoo.com/care/cockatoo/glossy-black and https://www.animalinfo.com.au/fact_sheets/view/4/15/161/fs:An_Experience_with_Glossy_Black_Cockatoos).

to be continued in https://www.inaturalist.org/journal/milewski/67970-why-is-the-glossy-cockatoo-so-brainy-part-2...

הועלה ב-יולי 6, 2022 12:02 לפנה"צ על ידי milewski