With all the online crow trivia listicles that are already floating around it can be hard to come up with tidbits that are both factual and interesting. I was up the the challenge though and am hoping I found at least one thing every reader didn’t know. Let me know how I did in the comments section!
1. Avocados are toxic to crows.1
Well, really avocados are toxic to most birds, and many other kinds of domestic animals. Avocados contain a molecule called persin, which the plant produces as a fungicide. In birds, it can cause damage to the heart tissues, difficulty breathing, lethargy or even death. The resplendent quetzal is a rare exception in that it can not only tolerate avocados, but is considered a crucial seed distributor of the plant. So next time you’re considering sharing your Chipotle leftovers, make sure you didn’t order extra guac.
2. Scavenging accounts for very little of a crow’s diet2
Scavenging, meaning the consumption of dead plant or animals material, is a crucial part of our ecosystem that is commonly the recipient of unfair prejudice. American crows often get thrown in with this lot, and while there wouldn’t be anything gross or insulting about this if it were true, it simply isn’t. Whether you’re in the city or the wildlands, scavenging and active predation account for only a minority of a crow’s diet. The bulk of their daily meal is made of human refuse, invertebrates and worms. In the cities, about 85% of their diet is human refuse, whereas in exurban and wildland areas human refuse and invertebrates account for roughly equal proportions of their daily food (about 35% each).
This scene is not as common as many people think! Photo: W. Perry Conway/CORBIS
3. There’s only three places with no native corvids3
New Zealand, the southern part of South America and the poles (ok so I guess technically 4 if you want to be a stickler about it). Why this is remains largely mysterious, but it probably has to do with where and how these birds radiated out from their ancestral origins.
Global corvid distribution. They’ll be our avian overlords soon enough I’m sure.
4. They have some of the best spatial memory of any animal4
Every year Clark’s nutcrackers and pinyon jays store tens of thousands of seeds to sustain them through the lean winter months. If they fail to retrieve enough they’ll perish, so a good spatial memory can literally be the difference between life and death. To deal with this mental load, these two species (and other food caching birds) have a huge hippocampus relative to the rest of their brain. With the spatial memory part of their brain super charged they’re able to retrieve 20,000-30,000 seeds with 90% accuracy or better. I can’t usually retrieve my cell phone what that kind of accuracy so I certainly tip my hat to them!
Clark’s nutcracker. Photo: Minnesota Birder
5. They account for the largest songbird in the world.5
The common raven is marginally the largest songbird of the world with a 4.9ft wing span and weighing in at up to 4.5lbs. An extremely close second is the thick-billed raven, which is native Ethiopia and has limited range in some surrounding countries. In fact, the two are so close in size that there are conflicting reports of which is bigger depending which publication you look at3,5. Scientists finally resolved this dispute, however, and came to the consensus that the common raven is larger for the 2009 publication of the Handbook of the Birds of the World.*
Thick billed raven. Photo: Ignacio Yufera
*This section has been updated from a pervious version which incorrectly stated that the thick-billed raven was larger.
Literature cited
- http://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/avocado
- Marzluff, J.M., McGowen, K.J., Roarke, D. and Knight, R.L. 2001. Causes and consequences of expanding American crow populations. in Avian ecology and conservation in an urbanizing world (J.M. Marzluff, R. Bowmanm and R Donelly, eds). Kluwer academic Press, norwell, Ma.
- Madge, S. and Burn, H. 1999. Crows and jays. Princeton, New Jersey: Princeton University Press 1999.
- Marzluff, J.M. and Angell, T. 2005. In the company of crows and ravens. Yale University Press.
- dos Anjos, L., Debus, S., Madge, S., & Marzluff, J. (2009). Family Corvidae (crows). In J. del Hoyo, A. Elliot, & D. A. Christie (Eds.), Handbook of the birds of the world (Vol. 14, pp. 494e641). Barcelona, Spain: Lynx Edicions.
corvidresearch.blog 
Loved this “trivia”. Love this website. Love crows. Thanks and keep it comin’.
Every time I get here I learn something new. Thanks
Knew about avocados being poisonous (apple seeds as well due to the trace amounts of arsenic) and the fantastic spacial memory. I also knew corvids were widespread but not resident in the poles – but didn’t know they also are absent from New Zealand. I had no idea that they are not scavengers. I’ve learned the hard way that they eat earthworms, however, since my African pied crows managed to get capillaria (parasite) from snacking on them. (APCs are susceptible to capillaria whereas American crows appear to be immune.) And that thick billed raven is phenomenal. Thanks for putting this list together.
Great info! I am a Crow & Raven lover and there were things I did not know. Like Avocados being toxic! Also their diet. They are glorious creatures who def get a bad rap. Thanks so much for the info!
Oh my. Love my crows and yours too. Your baby crow pictures remind me of how goofy and cute they are. R
This is a great blog, informative and well written, for me specially because I’ve always found crows facsinating, but I do not have a naturalist’s patience.
One question: I live in the New York Metropolitan area (Jersey City to be exact), and crows are extremely rare around here. I’ve spent time in upstate New York, and have occasionally seen them, but they keep their distance (i.e. >100meters). On the other hand I’ve been in places like Sri Lanka where they are all over the place, not very shy, and fun to watch. I have a video of one looking at me from a distance of a few meters and cawing. Why is that? Different breeds? Pushed out by seagulls and pigeons?
Happy New Year,
Jacob
Thank for your kind words, Jacob. As for your question, for the best answer I’d head on over to my crow colleague and former NY based crow researcher Jennifer Cambell-Simth’s site (http://coyot.es/thecorvidblog/) to ask your question. She will likely be much better equipped to address the peculiars of our eastern crows and of that area specifically. In general though, yes the house crow (the species you encountered in Sri Lanka) are even more synanthropic than our American crows. If you head to Jennifer’s old stomping grounds in Ithaca though, I assure you, you will find plenty of friendly American crows!