How brainy are ground parrots relative to Australian birds in general?

In my last Post, I showed that certain species of terrestrial parrots in Australia are the least brainy parrots on Earth, helping to explain why they are threatened with extermination by introduced predators.

However, Psittaciformes are the brainiest of all the orders of birds, reminding us that everything is relative. The obvious question thus arises: 'are even ground parrots brainier than comparable birds in orders other than Psittaciformes?'

The answer can be found by reading between the lines in Tables 1 and 2 in https://www.researchgate.net/publication/262565451_Relative_brain_size_in_Australian_birds, which provides average values for braininess for most orders of birds and many of the families of passerine birds (https://en.wikipedia.org/wiki/Passerine) in Australia.

If zero represents average braininess for Australian birds in general, then some orders (or passerine families) have averages in the negative range and others have averages in the positive range. For example, the least brainy orders of Australian birds are Galliformes (https://en.wikipedia.org/wiki/Galliformes), Casuariformes (https://en.wikipedia.org/wiki/Casuariiformes) and Podicipediformes (https://en.wikipedia.org/wiki/Grebe), all of which have averages of -0.27 or less.

At the opposite end of the spectrum are Psittaciformes and Strigiformes (https://en.wikipedia.org/wiki/Owl), which are by far the brainiest Australian birds with average values of +0.2 or more.

The least brainy parrots have values of +0.035, which remains on the positive side. In other words, even ground parrots (e.g. Pezoporus wallicus and P. flaviventris, see https://en.wikipedia.org/wiki/Pezoporus) are brainer than the average bird in Australia, brainier than most orders of birds in Australia, and brainier than most families of passerine birds in Australia.

We can narrow down the comparisons by focussing on other seed-eating birds.

Estrildidae (https://en.wikipedia.org/wiki/Estrildidae) are a mainly seed-eating family of passerines, and they average -0.03. This makes them slightly less brainy than the average Australian bird, compared to ground parrots which are slightly more brainy than the average Australian bird.

The comparison widens when applied to Columbiformes (https://en.wikipedia.org/wiki/Columbidae), which average -0.24. Pigeons and doves are brainier than Galliformes (Australian average -0.31), but they are the fourth least brainy order of Australian birds. This means that ground parrots are much brainier than doves with comparable habitats and diets.

Passerine birds include several brainy families, but the only ones in Australia with average values beating the value for ground parrots are (in order of increasing braininess):

• Pachycephalidae +0.05 (https://en.wikipedia.org/wiki/Pachycephalidae),
• Acanthizidae +0.06 (https://en.wikipedia.org/wiki/Acanthizidae),
• Ptilonorhynchidae +0.08 (https://en.wikipedia.org/wiki/Bowerbird), and
• Pomatostomidae +0.09 (https://en.wikipedia.org/wiki/Australo-Papuan_babbler).

The family Corvidae (https://en.wikipedia.org/wiki/Corvidae) is renowned for its braininess, but the Australian species average only +0.03, slightly less than the value for ground parrots.

So, what these data show is that parrots are so extremely brainy that even their most decephalised members - with their inconspicuous colouration, minimal sociality, crepuscular activity and secretive habits - remain among the brainiest birds in Australia.

Given this perspective, how can we explain the particular vulnerability of ground parrots to predation?

One answer is that ground parrots have particularly slow reproduction and growth. This is related to their specialisation for some of the nutrient-poorest environments on Earth, particularly heathland (kwongan https://en.wikipedia.org/wiki/Kwongan in Western Australia and wallum https://en.wikipedia.org/wiki/Wallum in eastern Australia) and hummock grassland (https://www.anbg.gov.au/photo/vegetation/hummock-grasslands.html).

The result may allow us to reframe the plight of ground parrots in a way. True, they are among the most threatened of Australian birds, but given their slow reproduction they might have been extinct already were they not as brainy as they are.

Publicado el diciembre 31, 2021 06:00 MAÑANA por milewski