Parrots and Songbirds
Intro
Songbirds are the closest related group to Parrots and they share a number similarities due to this, such as both possessing varying degrees of vocal mimicry and having similar brain regions that produce and learn sound, as well as species from each group possessing the ability of allospecific vocalisations.
This section aims to highlight what makes parrots unique, as well as how different evolutionary pressures have caused songbirds and parrots to differ since they diverged over 50 million years ago.
Similarities
The main similarity between parrots and songbirds is that they have similar brain anatomy, both possessing vocal nuclei that do similar jobs.
They also share dense neural packing in thier forebrains (part of the telencephalon). The extent of this density can be compared to the brains of primates with much larger brain masses, which gives parrots and songbirds a higher cognitive power per unit that most mammals, and is likely a large factor in there excellent mimicry skills.
(Brain weight)
(The number of neruons x10-6)
Differences
One of the main differences between Parrots and Songbirds comes from the 2 pathways to vocalisation (talked about in module 1). While songbirds are still able to vocalise without the anterior (vocal learning) pathway, parrots have a complete breakdown in harmonic structure when it is removed and are unable to properly vocalise.
This is likely due to the 2 pathways being more interconnected in parrots, with the vocal nuclei in the anterior pathway also having a function in maintaining normal vocalisations, and without these components, the posterior (vocal production) pathway cannot operate functionally.
Another difference comes from the syrinx (vocal organ) anatomy, with songbirds often having more intrinsic muscles which help with accurate sound production.
These intrinsic muscles are likely a specialisation to help mimic vocalisations as they are found in all vocal learning bird groups, and arent present in related groups such as falcons.