Nature’s Garbage Collectors: Guest Blog by Nick Rhodehamel
For a long time, I used to say that crows like nothing better than pizza crust. But that’s not strictly true; crows seem to eat and to enjoy most table scraps. They don’t obviously roost near our house, but they must watch us because when we put out stale bread, old pasta, or anything else that’s edible, they descend within minutes. Sometimes you hear a call go out, and a group arrives; other times a single one arrives, but usually he’s soon followed by more. Often there are as many as 10 in our yard. We don’t tell our neighbors that rotisserie chicken leftovers are given to the birds.
I’m talking, of course, about the ubiquitous American crow (Corvus brachyrhynchos) here. They are large, fully black birds that range over most of North America. There are two other North American crow species that are virtually identical to the American crow but that have more limited ranges–Northwestern crow (Corvus caurinus), found in the Northwest, and Fish crow (Corvus ossifragus), found along the south Atlantic coast.
Crows are intelligent birds who have as many as 250 unique calls and make and use tools. They are highly social, live in close-knit family units, and are rarely alone. Crows take mates for life. They are highly adaptable and will live almost anywhere in natural or human-shaped environments, but they prefer open spaces or the margin of wooded areas; they don’t like unbroken forests or deserts. When not feeding from dumpsters or my backyard, they eat earthworms, insects, seeds, snails, small rodents, and song bird eggs and young. They eat most anything. They also help clean up road ways of smashed squirrels, rabbits, and whatnot; crows are not specialized as scavengers, though, and carrion is a small part of their diet.
I have always liked crows because they seem to have a strong sense of themselves and always seem to be having a good time. A group of them regularly gathers in my yard, sitting in various trees and calling to each other in their characteristically raucous way. I assume they’re swapping stories of food finds or maybe just wasting time.
A group of blue jays (Cyanocitta cristata) also gathers here. They too are social, intelligent, travel in packs, and seem to enjoy life. Jays too are omnivores and their choices in food and the source thereof is much the same as those of crows; so they’re competitors of crows. And they don’t like crows, and crows don’t like them. I often see groups of jays dive bombing the larger, less agile crows.
Sometimes, both crows and the jays will assemble and vie for our trees and lawn. They call to each other, likely insults and threats. When jays try to take a spot claimed by the crows, they are forced back. Then the same happens when the crows try an offensive. After a while, the conflict loses energy and individuals drift off until there’s no one left.
These crows seem to think my yard is theirs. Either that or they have a simple abiding hatred of turkey vultures (Cathartes aura) as well as jays. Twice a year turkey vultures migrate through in small groups, going south in October and back north in March. We have several mature Douglas firs that the vultures like to rest in and spend the night. If the crows discover the vultures, though, they go crazy, making a tremendous din, calling in reinforcements, and dive bombing the vultures; there will be as many as 25 crows. Finally, the vultures take wing, the band(s) of crows trailing after them. How far the crows follow I don’t know.
But not all is well with crows. West Nile virus, first identified in North America in New York City in 1999, is a threat to them as well as humans. The virus is effectively spread by mosquitoes, which carry the highest virus concentration in fall. Crows are very susceptible to it and were among its first casualties. So susceptible are crows that they function as a reliable biological indicator of the human disease potential.
In the initial onslaught of the virus and as it spread, crow populations were devastated–overall, somewhere in the neighborhood of 45% of the American crow was killed. A laboratory study showed that 97% of crows infected with the virus die. Another study of captured, live crows found that only 3% of those crows had antibodies to the virus in their blood, confirming that not many infected crows survive.
Nevertheless, crow is not considered an endangered species. Crow deaths from West Nile virus seem to be declining with time and the rates have leveled off. In some cases, crow numbers have increased. Nationwide, by 2006, surveys of crow numbers indicated only a 13% decline relative to 1999.
Several factors are responsible for these trends. Among them are increased resistance to the virus within crow populations and an apparent loss of virulence by strains of West Nile virus. But the most significant factor is probably the structure of crow society. Crows are among a small minority (about 3%) of birds and mammals that breed cooperatively. Their small family units include nonbreeding “helpers”. These are both young male and female birds who are generally offspring of the breeding pair and who contribute to caring for and rearing young. Helpers will delay moving away and starting their own families in response to the needs of their parental group. This intragroup cooperation provides a safety net for crows, without which the loss of one of the breeding pair would probably mean the loss of the entire next generation.
I know that some of my neighbors find the crows annoying. Crows make lots of noise, and they certainly cannot be considered “song birds”. On trash day, they tear open garbage bags and strew the refuse around, never picking up after themselves. But they also have a function as Nature’s garbage collectors, eating road kill and old pizza. They contribute to our well being by thinning the numbers of rats, mice, and rabbits that plague our homes and gardens. And they provide a consistent source of entertainment and theater in your backyards.
Loved the article on crows & blue jays. Have both crows & jays frquent our rural yard. Have 3 acres & enjoy all the wildlife & birds than come. Did not know crows mate for life, interesting fact I did not know.
Dear Carol Ann,
I’m glad you liked the article. Please post again.
Loved the article! I too, am an admirer of the entertaining Crow.
Thank you and thanks for taking the time to post, Sherrilyn.
So interesting! I get so angry at crows who prey on baby rabbits, but at the same time I respect and enjoy their clever survival skills
Whether we appreciate the comparison or not, crows are a lot like humans — they are noisy, bossy survivors.
Dear Kate,
I’ve shooed crows out of mulch in a blueberry bed where baby bunnies were nesting, so I know what you mean. And later in the season, I probably cursed the same rabbits that I had saved when they chewed the new blueberry growth. In addition, to being noisy and bossy survivors, they take care of their own members.
I loved this article on the Crows. Even though they wake me up on most mornings with their loud sounds–they are much appreciated on my small farm.
Thanks so much for taking the time to write the wonderful articles. Bob
Thanks, Bob, I’m glad you enjoyed the piece. And that’s the nicest compliment I’ve had all day.
I always think of crows as little men in tail coats. Their upright posture and preference for walking or hopping unless they really need to fly reinforces that image. They really appear to know what the white line at the side of the road means and will take a leisurely stroll off the traveled roadway as a car approaches and wait on the other side of the line for it to pass. As a teenager, I cared for an orphaned crow with blue eyes. I also love the crow’s larger cousin the raven. They are all so clever.
Dear Lois,
Thanks for sharing your image of crows. It’s very apt. Also, I read your post to my wife, and she wanted you to know that she got a kick out of it. It’s interesting to consider the insult “bird brain” when there are such clearly intelligent birds as crows and ravens around.
one of my favorite birds – I tend to really like the preditors- redtail hawk, all owls and the sound of the ravens flying by at head level at the Grand Canyon is almost as good as the redtail hawk cry . . .
Dear JP,
Thanks for taking the time to post. I’m pretty fond of ravens too. I’ve seen them at 19,000 feet digging into food caches that were not buried deeply enough. That’s a smart, self-possessed bird.
The crows in my neighborhood have been seen eating road kill quite often. Hate to see dead animals (except voles), but at least their death feeds another of nature’s creatures. My biggest problem with crows is that their caws cause my schnauzer to go ballistic. I think he thinks they are teasing him.
-Jeff
Dear Jeff,
I can easily imagine a schnauzer going ballistic. When the crows come, our cats are glued to the windows and make a sort of cackling noise. My guess is that they’d be afraid of the crows if they ever got that close.
Thank you for your description of these noisy birds. I too put out all kinds of dinner scraps,loved by the jays, woodpeckers and cardinals. I wait till morning to put out the treats, so not to feed the night time adventurers. Everything is gone by noon. I always know when the crows arrive by their noisy chatter. I’m glad to know I’m not alone at sharing the goods and not trashing leftovers.
Dear Elizabeth,
Yes, I like putting out stuff that would otherwise rot for a while in a bag and then in a landfill. I’ve always felt slightly guilty about attracting crows to my yard, so I too am glad to hear other people do the same thing. Also, I know what you mean about night time adventurers—we have lots of raccoons, and while kind of cute, they carry lots of diseases I’m not wild about getting. Thanks for taking the time to post.
agreed! I am always reassured by the sound of a crow’s “rattle”. I imagine 2 crows, exchanging words of wisdom, an having a few chuckles along the way!
Dear SDP,
I agree with you too. Any number of times I can recall spending time in woods or on mountains and really appreciating crows and ravens stopping by to see what I was doing. It was like receiving company.
I too feed the crows and get great enjoyment from them. One day I heard on the radio, “Willamette biology Professor David Craig recently co-authored a study, published in Animal Behaviour, which supports many people’s anecdotal claims that birds recognize and remember people they consider to be a threat and friend.”
Dear Karen,
That’s very interesting. I’ve always heard that crows recognized individuals. My crows, though, never seem to warm up too much and always appear pretty wary. I wonder what sort of methodology Professor Craig used to test his hypothesis.
I love Crows. They provide a show better than anything on TV.
Dear Cynthia,
I’m with you. Thanks for taking the time to write.
I also noted their decline in numbers after the initial onslaught of west nile virus. Previously the crows would find crickets fly up to my roofline and either eat or play with them. The crickets could sometimes escape and find their way into my attic through the ridge vent. I have not had a cricket in my attic for three years, not that I’m unhappy about that. Their “songs” and beautiful shiny almost iridescent black are very appealing.