Social Complexity Gives Parrots Big Brains

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Written By Animalcognition

Parrots have rather large brains. In fact, relative to their body weight, their brain size-to-body size ratio is about the same as advanced primates like chimpanzees and orangutans.

“Humans have these really big brains, but guess what, parrots have really big brains too. In fact, if you overlay a graph of brain size to body mass for parrots on top of one for non-human primates, they sit in a perfect line,” says Dr. Andrew Iwaniuk of the University of Alberta.1

But what exactly led to the development of these large brains? Research suggests that parrots owe it to the complexity of their social lives.

Scientists observed both wild and captive monk parakeets to gain insights into their social networks and behaviors. They found that typically, individual parakeets prefer to spend time with one other individual parakeet (most commonly their mate). Pairs were identified as the “fundamental unit” of their social structure, but the birds also held other relationships as well, in varying degrees of closeness. Additionally, hierarchies were determined by the outcomes of confrontations: the birds that lost would find themselves positioned lower down the social ladder than those that had won.

The complexity of these societies bears striking similarities to that of societies formed by other cognitively advanced species with large brains. Because of this, the researchers believe that there is a strong correlation between social complexity and brain size.

Video of wild monk parakeets:

The paper’s abstract:

In many species, individuals benefit from social associations, but they must balance these benefits with the costs of competition for resources. Understanding how these competing factors generate diversity in social systems is a major goal of behavioral ecology, but one that has been hampered by a lack of basic data quantifying many aspects of social structure and associations. Although parrots are generally assumed to have complex social groups, few studies have quantitatively examined these assumptions about parrot social structure.

We critically assessed 4 assumptions about parrot socioecology using data from captive and wild groups of Monk Parakeets (Myiopsitta monachus). We evaluated (1) whether pairs are the fundamental unit of parrot social structure, (2) the patterns and extent of fission–fusion dynamics, (3) patterns of aggression and dominance hierarchy structure, and (4) whether individuals share foraging information. We found evidence that supported pairs as the fundamental unit of social structure, although these close associates were not always heterosexual breeding pairs and were sometimes trios. Fission and fusion of subgroups were common, and the amount of fission–fusion dynamics varied across flock types and by fission–fusion dimension, but the amount of variation among dimensions was consistent across replicate captive social groups.

Despite these levels of fission–fusion dynamics, study of aggressive interactions in our 2 captive groups indicated that dominance hierarchies existed. Hierarchies were moderately linear (0.7) but not steep (<0.1). Finally, we found no evidence that Monk Parakeets share foraging information among groups through active vocal recruitment to foraging flocks. We compared these patterns with those documented for other species of parrots and other cognitively complex large-brained species. We consider the implications of our results for the study of the evolution of complex sociality and highlight several future directions for parrot socioecology research.

This article was written by Amanda Pachniewska, founder & editor of


1 – Andrew Iwaniuk, “This Bird Is No Airhead”
Natural Sciences and Engineering Research Council of Canada 

2 – Elizabeth A. Hobson, Michael L. Avery, and Timothy F. Wright
(2014) The socioecology of Monk Parakeets: Insights into parrot social complexity.
The Auk: October 2014 Vol. 131