When it comes to birds, brain size matters. A larger brain generally allows for more complex behavior and cognition. But which bird species has the biggest brain compared to its body size? The African grey parrot has the largest brain-to-body mass ratio of any bird. Their advanced cognitive abilities are likened to a 3-5 year old human child. African greys can learn hundreds of words, count, and even reason abstractly. Other birds with impressively sized brains include crows, ravens, and macaws. In this article, we’ll explore the birds with the biggest brains and what makes them such intelligent creatures.
What is Meant by Brain Size?
When scientists talk about brain size, they are referring specifically to the weight or volume of the brain. A larger, heavier brain has more neurons and synaptic connections, allowing for greater information processing power. However, raw brain size doesn’t tell the whole story. An elephant has a much larger brain than a human, but that doesn’t make elephants smarter than us. What matters more is the brain-to-body mass ratio – how big the brain is relative to the entire body. Animals with large brain-to-body ratios are generally more behaviorally and cognitively advanced.
How is Bird Brain Size Measured?
There are a few ways researchers can measure avian brain size:
- Directly weighing brains after dissection
- Measuring brain volume by displacement or imaging techniques
- Estimating brain volume based on endocranial volume (volume of cranial cavity)
Weighing brains directly provides the most accurate measurements, but requires sacrificing birds for research. Non-invasive methods like MRI scans can measure brain volume in live specimens. Endocranial volume also gives reasonable estimates, as the interior skull cavity closely matches overall brain dimensions.
What Bird Has the Largest Brain Size Relative to Body Size?
The African grey parrot has the largest brain-to-body mass ratio of any bird species. Despite weighing only about 400 grams, the African grey parrot’s brain averages 9.5 grams – just over 2% of its body weight. The next largest ratio belongs to crows at 1.6%. In comparison, the human brain makes up about 2% of our body mass. The tortoise brain is only 0.2% of its body weight.
So although African greys are dwarfed in size by many other parrots, they pack a lot of brain power per ounce. Other birds with impressively large brain-to-body ratios include other parrot species, corvids (crows, ravens, and jays), hornbills, and some birds of prey like falcons.
Why Do African Greys Have Such Large Brains?
There are a few key reasons why African greys have such disproportionately large brains:
- Highly social nature – Social interaction and coordination requires greater intelligence.
- Food extraction skills – Extracting seeds/nuts takes cognitive skill.
- Foraging innovation – They have flexible foraging strategies.
- Communication complexity – They have large communication repertoires.
African greys live in large, complex flocks with extensive vocal communication. Their strong social bonds, mimicry abilities, and aggression avoidance behaviors likely require greater brainpower. Extracting and manipulating food like seeds or nuts also demands cognitive coordination. African greys are highly innovative foragers, using tools and solving problems to obtain food in the wild. Supporting their impressive learning capacities takes a lot of brain matter!
Brain Power Rankings: Top 5 Birds by Brain Size
Based on brain-to-body mass ratios, these birds have the largest brains:
- African grey parrot
- Scarlet macaw
- Green-rumped parrotlet
- Kea
- Brown-headed cowbird
Parrots take several spots thanks to their large brains relative to their body size. Keas and crows also rate very highly. Let’s look closer at what makes these avian Einstein’s brains so big:
African Grey Parrot
With the largest proportional brain size, the African grey is renowned for its intelligence and speaking abilities. Studies have revealed counting comprehension, abstract reasoning, and communication skills comparable to a young human child. Wild African greys use tools, solve problems, and have complex social structures.
Scarlet Macaw
Scarlet macaws have the largest absolute brain size of all parrots. These long-tailed, brightly colored parrots are highly playful, social, and vocal. They can live for over 75 years and require lots of mental stimulation. Their large brains allow macaws to form close bonds, communicate, and remember cues over a long lifespan.
Green-Rumped Parrotlet
Weighing just 18 grams, this tiny parrotlet has an extraordinarily large brain relative to its tiny body. Parrotlets live in large flocks requiring social coordination. They build nests, use tools, and can be taught words and tricks. Their brain expansion may be linked to the cognitive demands of their complex sociality.
Kea
This mountain parrot is New Zealand’s largest. Keas are incredibly playful and the first bird discovered to use tools in the wild. Their natural curiosity and problem solving lead them to manipulate objects in innovative ways. They have advanced understanding of object displacement and mechanics.
Brown-headed Cowbird
Known for laying eggs in other bird’s nests, brown-headed cowbirds have unusually large brains for a songbird. Their brains are over 50% larger than other similar blackbirds. This allows them to remember locations of dozens of host nests rather than building their own. Cowbirds monitor nests and synchronize egg-laying precisely.
Brain Size and Intelligence
Does brain size equate intelligence? Not exactly. Total brain size doesn’t directly correlate with greater intelligence within a species. For example, men generally have larger brains than women due to larger body size, but there is no difference in IQ. However, between species brain size indicates potential for more complex cognition. Bigger brains allow for more neurons, connections, and processing power. Social life also seems to drive the evolution of large brains across diverse animal taxa. The largest brained species tend to live in more social-dependent, coordinated groups. Human evolution likely favored larger brains to navigate our ultra-social world. We can see this same trend in highly social birds like parrots and crows. Their big brains allow greater information processing and social competence required in sophisticated flocks.
Brain Architecture
Looking deeper than size, specific architecture and connectivity patterns matter too. Parrots have a large forebrain (cerebrum) relative to other birds. The cerebrum is linked to higher cognition and long-term memory storage. Parrots also have highly developed frontal lobes for judgement, problem solving, and flexible behaviors. African greys and other big brained avians show neural scaling and complexity approaching that of primates. Insights into how parrot brains achieve higher cognition could advance our understanding of intelligence differences between species.
Conclusion
For its combination of large absolute brain size and disproportionately high brain-to-body ratio, the African grey parrot stands out as the bird with the largest brain. Their advanced cognitive abilities are supported by a brain as cognitively capable as apes and dolphins. Other highly encephalized birds include corvids, macaws, and parrotlets, which also live in large social groups requiring greater mental capabilities. While brain size alone doesn’t determine intelligence, the social and behavioral complexity of large brained birds reflects their greater capacity for information processing, communication, problem solving and other cognitive skills characteristic of intelligence. Comparative studies of avian neuroanatomy and cognition will continue elucidating the evolution and function of the brains of birds.