Clever City Crows: How Corvids Conquered the City

What is the most intelligent animal you can think of? Species that likely come to mind are perhaps apes, cetaceans, or elephants. However, in spite of their intelligence, most of the species from these groups are not as abundant as they used to be. Humans have changed the world through climate change, pollution, and changing land use, impacting the habitats of many wild animals. We build large cities where most species, however intelligent, will not be able to survive. There is, however, an exception to this phenomenon—namely a peculiar group of intelligent animals: corvids. It seems these clever, cawing birds have used urban environments to their advantage to not only survive, but thrive.

A Versatile Family

Corvids are a family of medium-sized passerine birds. The family Corvidae contains quite a lot of common species such as crows, ravens, magpies, jays, and jackdaws. They are widespread across all continents and live in a wide range of habitats, even in the wild. For example, they’re found in tropical and deciduous forests, on plains, savannahs, coastal areas, and now—more recently in their evolutionary history—in cities. So, what makes them so adaptable? And how did they adapt to urban environments?

Trash to Treasure

Corvids are a perfect example of adaptation to life in the city, as they have found many ways to make a living in urban environments. Firstly, corvids use their generalistic diet. They are highly omnivorous birds, eating a wide range of foods such as insects, fruits, nuts, small rodents, and carrion. This flexibility in diet allows corvids to make use of novel food sources as they come upon them. In cities, corvids are able to use this to their advantage, as urban environments contain many sources of nutrients produced by humans. Fourteen species of corvid have been found to consume artificial foods in urban settings (Benmazouz et al., 2021). Artificial food sources such as garbage bins and bird feeders are a great source of nutrition for a corvid, as these are widespread and numerous across cities.

Urban Living

In addition to artificial foods, corvids also use artificial nesting sites where they build nests using artificial materials. They have found places to nest that would not be available to them in the wild, such as poles, roofs, attics, and exotic trees that are not native to the area. Nests are then sometimes built using materials found in the city. One study by Hiemstra et al. (2023) even found magpies and crows using anti-bird spikes to build their nest. These spikes were ripped off buildings that placed them to repel birds and put together to form a spiky, protected nest.

Street Smart

Finally, corvids also used their smart thinking to adapt their behaviour to urban environments. Corvids in cities are generally more tolerant and less vigilant toward humans, as they have grown used to the presence of humans around them. Additionally, some crows in Japan have figured out how to crack nuts using cars. They drop hard-to-crack walnuts onto a road and wait for a car to run over it, essentially using the cars as nutcrackers to obtain otherwise unreachable nutrients (Nihei & Higuchi, 2002).

Conclusion

All in all, corvids have adapted to living in urban environments in various ways. Populations of many corvid species actually increase in cities compared to populations in their natural environments because of the high food availability and many nesting locations (Benmazouz et al., 2021). I would make the argument that corvids might be the smartest animals, as they have found ways to use human-made environments to their advantage without being a nuisance to the humans providing the beneficial circumstances. These birds should be appreciated for their intelligence and their amazing adaptiveness, and we should look more into how this amazing family manages to have such plasticity in behaviour and physiology.

 

References

Benmazouz, I., Jokimäki, J., Lengyel, S., Juhász, L., Kaisanlahti-Jokimäki, M., Kardos, G., Paládi, P., & Kövér, L. (2021). Corvids in Urban Environments: A Systematic Global Literature review. Animals, 11(11), 3226. https://doi.org/10.3390/ani11113226 

Hiemstra, A.-F., Moeliker, C. W., Gravendeel, B., Schilthuizen, M., Naturalis Biodiversity Center, Institute of Biology, Leiden University, Natural History Museum Rotterdam, & Radboud Institute for Biological and Environmental Sciences. (2023). Bird nests made from anti-bird spikes. In DEINSEA (Vols. 21–25). https://www.hetnatuurhistorisch.nl/fileadmin/user_upload/documents-nmr/Publicaties/Deinsea/Deinsea_21/Deinsea_21_17_25_2023_Hiemstra_et_al.pdf

Nihei Y., & Higuchi H. (2002, 1 juli). When and where did crows learn to use automobiles as nutcrackers? Copyright © 2007-2008. https://tohoku.repo.nii.ac.jp/records/1503