Bird Brain: The Complex Behaviors of Crows and Corvids

By ​​Alex Cesaretti

From Aesop’s fable of the “Crow and the Pitcher” to Odin’s twin crows, memory and thought, Crows appear as an icon of wisdom and mischief across mythology and pop culture. Perhaps you yourself have heard from a friend of a friend how, in exchange for food scraps, crows might leave shiny objects like coins or screws on porches and even remember a specific person to give these gifts to. So how are these birds so different from the rest? Different from the geese that refuse to move out of the way of an approaching car or unassuming pigeons that shuffle under your boot for crumbs? And how do we even measure intelligence anyways? ​

Crows belong to the Corvidae family, thought to be the smartest class of birds, with the family which parrots belong to, Psittacidaes, coming in a close second. Nicknamed the “feathered ape” for their intelligence, Corvids actually have a brain to body size ratio similar to that of chimpanzees. Notably, the areas of their brain that function similarly to our prefrontal cortex are significantly larger than other bird families (Kersten et al., 2024, para 2-4). However, this fact still leaves them with brains about as light as ten paperclips and the size of a walnut. Corvids compensate what they lack in size with the density of their neural networks. Researchers cite that their brains have twice the amount of neurons per unit space than primate brains and four times as many as rodent brains (Olkowicz et al., 2016, abstract 1 and results).
Equipped with a physically superior brain to their bird relatives, Corvids showcase immense social complexity with great variability in behavior from bird to bird. Rooks, for example, are known to live in communities up to 60,000 in number and mate for life. They also understand social hierarchies via transitive inference (A>B and B>C so A>C), and remember specific birds by visual recognition or call (Clayton & Emery, 2007). They don’t just remember the appearance of other birds, but of other species as well. One study shows that American Crows who were caught by a researcher wearing a specific mask will scold anyone wearing the same mask for up to 3 years. Within these communities, Rooks might combat with other birds, and their partner will actually help them by participating in combat, sharing food, or by “bill twining”, which is thought to be an act of consoling by stroking their partners beak (Morell, 2021).
Perhaps more impressive are Corvid’s gathering and food caching habits. Clark’s Nutcracker’s cache up to 33,000 pine seeds and can remember their location months after the fact. Some species, specifically ravens and scrub-jays, are cognisant of other birds watching their caching activity. They have a tendency to hide their caches behind barriers or in darker locations, and if they know they are being watched by a bird higher in their social order they will actually return to that cache and move it elsewhere and even continue to move it after that. Interestingly, birds who have stolen other bird’s caches are the only ones to exhibit this behavior, with “naive” birds just caching out in the open (Clayton & Emery, 2007). Another bird, the Caledonian Crow, is the only animal besides humans to use hook shape tools in the wild (Weir et al., 2002). They use them to retrieve hard to reach food like an insect in a tree or a worm from a crevice, and recognize when a certain hook tool is higher utility than another and will keep that more valuable hook safer than their other stick tools (Klump et al., 2021). 
Research on Corvids is limited and has really only begun in the past 30 years, meaning we have only taken a glimpse into these birds' amazing behaviors. When it comes to research like this, it is usually accompanied by questions of intelligence, almost always in comparison to humans. But how should we define intelligence? What does it mean to be intelligent life? If we cannot memorize the location of 33,000 nuts like some Corvids can, does that make them more worth saving? Does this fact make Corvids more valuable and worthy of conservation? The lives of animals are something we can never fully understand, especially when we barely understand our own consciousness. Questions like these become only more prescient in our quickly evolving world, and our answers at best insufficient. That doesn’t mean we shouldn’t try. 
References
1. Kersten, Y., Moll, F. W., Erdle, S., & Nieder, A. (2024). Input and output connections of the crow nidopallium caudolaterale. eNeuro, 11(4), ENEURO.0098-24.2024. https://doi.org/10.1523/ENEURO.0098-24.2024
2. Olkowicz, S., Kocourek, M., Lučan, R. K., Porteš, M., Fitch, W. T., Herculano-Houzel, S., & Němec, P. (2016). Birds have primate-like numbers of neurons in the forebrain. Proceedings of the National Academy of Sciences, 113(26), 7255–7260. https://doi.org/10.1073/pnas.1517131113
3. Clayton, N. S., & Emery, N. J. (2007). The social life of corvids. Current Biology, 17(16), R652–R656. https://doi.org/10.1016/j.cub.2007.06.070
4. Morell, V. (2021). A kiss to help forget a fight. Science. https://www.science.org/content/article/kiss-help-forget-fight https://doi.org/10.1126/article.32663 
5. Weir, A. A. S., Chappell, J., & Kacelnik, A. (2002). Shaping of hooks in New Caledonian crows. Science, 297(5583), 981. https://doi.org/10.1126/science.1073433
6. Klump, B. C., St Clair, J. J. H., & Rutz, C. (2021). New Caledonian crows keep “valuable” hooked tools safer than basic non-hooked tools. eLife, 10, e64829. https://doi.org/10.7554/eLife.64829