by Gillian Martin
Did a person but know the value of an enemy, he would purchase him with pure gold
Have you spent time looking for family members on genealogy websites? It’s great fun, isn’t it, to discover look-alikes and common traits among newly discovered relatives. There are birds likely around you every day that are related…but perhaps you were unaware? We want to reintroduce you to the family, Corvidae. You guessed it! Crows are among them, and people are inclined to downright hate them. But apart from three species of crows in North America, there are about fifteen other members in this family. They include ravens, jays, and magpies. They don’t all look exactly alike, but if you think about it long enough, you may come up with a few physical and behavioral traits they have in common.
They’re a nuisance, did you say? Yes, they tend to be aggressive and loud, and in some cases their sheer numbers make them a messy pest. The fact that ravens and crows are all black and have sharp, raspy, or guttural vocalizations, doesn’t endear them to us either. And a few family members are notorious nest predators. Most of us have a dry eye when we hear that an owl or hawk snatched the nestling of a crow. But oh! When a crow is a nest robber!!
Why are crows so abundant? They (and jays) are birds of ‘forest edge’ habitats. Their populations have grown since humans began fragmenting forests (thereby creating more ‘edges’) while also developing open spaces and planting trees where few existed. Our croplands, parks, golf courses and sports fields also provide suitable food and trees. Let’s not hold our breath waiting for birds to recognize which food sources and sites are off limits to them! In fact, some members are drawn to places where people recreate merely for the food subsidy that is associated with humans (Walker, Lauren E. et al 2015).
What advantages does the family have apart from the fact that their diet is so highly variable (which includes ‘harmful’ insects and rodents, by the way). Intelligence! A few are even known for innovation, problem-solving skills, mimicking, and learning from observation. Tests reveal that ravens and magpies can count up to seven (in their heads, of course). And as you know, several live in large social groups where they assist each other in multiple ways. (Elphick et al. 2001) But what good are they anyway?
The Cornell lab of Ornithology reports on research reported in the Auk and The Condor: “In the western U.S., researchers have shown that repeated long-distance dispersal events by Clark’s Nutcrackers are essential to establish and maintain Ponderosa Pine populations, and that Pinyon Jays help maintain the tree’s genetic diversity. And in the eastern U.S., Blue Jays speed forest fire recovery by increasing their caching effort after fires and selecting canopy gaps as cache sites….Since oaks and pines are important keystone species that themselves provide habitat for hundreds of animal species, such dispersal can have ecosystem-wide benefits."
There are three other benefits corvids provide which are less known. Most important is that they scavenge carcasses. This provides health benefits especially in places where we live. Second, like some other birds, they pick ticks and other invertebrates from the backs of large mammals. And third, species like ravens and crows make large stick nests which are inherited or usurped by owls. A take-away here for tree care providers is to avoid removing these large stick nests and the foliage that surrounds them.
Honestly now, do we like all our relatives? We can often appreciate something about them, agreed? Perhaps we can think of the Corvidae family that way. They are a part of the tree of life. They serve as the ying and yang that keep things in balance. And they make our planet more habitable.
Elphick, Chris, Dunning John B. JR., Sibley, David Allen, editors. National Audubon Society, The Sibley Guide to Bird Life and Behavior 2001. p 408-415, Publisher Alfred A. Knopf, New York
Lauren E. Walker, John M. Marzluff "Recreation changes the use of a wild landscape by corvids," The Condor, 117(2), 262-283, (6 May 2015)
Pesendorfer, M. B., T. S. Sillett, W.D. Koenig, and S. A. Morrison. 2016. Scatter-hording corvids as seed dispersers for oaks and pines: a review of widely distributed mutualism and its utility to habitat restoration. The Condor 118: 215-237
Thank you for this most informative article. It could be a chapter in a book.
For the record, I may be one of the ten people in the world who likes these birds. They’re clever and always fun to watch. So I’m always glad to see them.
Excellent and thoughtfully incisive exploration of a touchy subject which will hopefully bring some re-thinking of our attitudes towards this family of birds… we should realize that where they have become obnoxious, we may be largely responsible for that situation….