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Are There More Crows and Ravens in the Bay Area These Days?

by Adrian Cotter on March 27, 2018


I have a question about the growing population of crows in the Bay Area – SF Gate did an article on it in 2012 and I wonder what more current data shows. I live in West Marin and the Woodacre population has grown from a few to several hundred + in the last decade. They are a clear threat to our biodiversity out here, not to mention drowning out any dawn chorus, scaring birds, etc. Their raucous loud dawn and dusk vocalizations and numbers feel out of hand. What is happening and what can people do (besides not feed them)? -Caroline Warner, Woodacre

The only thing good enough for a crow is a shotgun.”

This was an opinion from 1919. It was a common one, if fish and game journals of the time are any judge. Crows were vermin fit only to be exterminated. And attempt to exterminate them we did: with shotguns, poison, and dynamite.

One myth we hold is that crows and ravens showed up in the Bay Area for the first time circa 1970. Early California ornithologists, like Joseph Grinnell and his predecessors, tell a different story, where crows and ravens were not uncommon and were over time driven off from where humans made cities: crows for the farms, and ravens for the ranches. Crows were commonly found nesting on Berkeley campus in 1872, but were gone by 1927. However they were still noted as common in Marin. Golden Gate Park even had a gamekeeper to control “unsavory” birds and animals.

Not everyone thought the same of crows as the sportsmen. Some questioned the research that showed crows as insatiable egg eaters and crop destroyers even back in the early 1900s, and decried it as research funded by the ammunition industry.

As the conservationist side of the argument began to win, and more birds began to be protected — they began to arrive — that is to return — in the Bay Area, albeit in rapidly growing numbers. The 2012 SFGate article holds true: populations of ravens and crows have continued to grow in the Bay Area and across the country, particularly in urban areas. Any increase in crows in Woodacre is likely a byblow of the increasing populations of crows found from Mill Valley to Fairfax.

It is a fact that crows are nest predators. But it is less certain how much they might impact an ecosystem. In a recent round-up of studies (2015 Madden, et al.) 81% had no negative impact (and in fact, in a small number of studies, they had a positive impact).

That’s not to say that crows don’t eat eggs, or nestlings, or don’t, or can’t have any impact in some circumstances (ravens are often a culprit with local endangered species: Point Reyes National Seashore removes ravens to protect Common Murre nesting). The counterpoint to this is that we rarely see the impact of other nest predators like squirrels or rats, or Cooper’s Hawks, or even house cats (two other much derided “Vermin” in the journals of the early 20th century), let alone understand the relationship and competition that exists between those species. But it may also be that we have seen nothing yet. In some parts of the country, crow roosts see tens of thousands and in some cases hundreds of thousands of birds taking part.

So the question is really: should we do anything about the crows?

The biggest thing to keep in mind is that crows are not the true threat to biodiversity — we are the threat. We have automobile terraformed much of the continent, fragmenting existing habitat and creating a consistent habitat in which some species thrive. Where there are species threatened by other species like the crow, it is loss and disruption of habitat that is likely the true cause.

The best thing we can do then, perhaps, is work and advocate for rich and varied habitats for the birds that we want, and to try to leave less space (and food) for the crow. Denser, habitat-rich cities, and better connected parks would help. Of course, there are limits to what we might do. San Francisco could control its corvid population by cutting down all its trees, and returning itself to its former dune habitat, but that seems an unlikely event!

The other thing that you could do to help is work to contribute to the growing set of citizen science data. Using iNaturalist or eBird you can help to answer what birds are there now, and how their populations might be changing over time. Enlist your neighbors (Cornell Lab of Ornithology has lots of great programs for kids and adults) and don’t just record the rare birds.

On a different (cynical or hopeful I can’t decide) note, maybe we ought to be thankful that there are a few bird species that look like they might survive the Anthropocene — and perhaps in numbers that would rival the birds in the air prior to European colonization. The raucous crow may not be the bird we wanted to have darkening our skies, but maybe it’s the bird that we deserve.

adrian-imageAdrian Cotter is an amateur naturalist based in Oakland. He works on websites for the Sierra Club for work. He has helped coordinate the (hopefully soon to be relaunched) SF Natural History Series for many years, is working to rejuvenate the Rotary Nature Center as part of Community for Lake Merritt, is a bioblitz junkie, and earned his Corvidae knowledge while mapping raven nesting in San Francisco.

Ask the Naturalist is a reader-funded bimonthly column with the California Center for Natural History that answers your questions about the natural world of the San Francisco Bay Area. Have a question for the naturalist? Fill out our question form or email us at atn at baynature.org!

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13 comments:

Josiah Clark on March 27th, 2018 at 8:11 pm

Oh man. If folks are not seeing an overwhelming rise in nest predation by corvids in the Bay Area they are not looking hard enough. There is not a single nesting species unaffected by the nearly 2000% increase in Ravens in the last 30 years (to say nothing of the other corvids).
It’s the cup nesters and precocial young that are hit the hardest. Also reptiles and small mammals. Corvids are amazing, and grossly overpopulated just like the people whose lead they follow. The real question is what are we going to do about it.

Constance Taylor on March 28th, 2018 at 7:23 am

Hi Josiah,
Can you post some resources and research regarding where your info is coming from? I’d love to learn more about Corvid population increase and nest predation.

Michael Meyer on March 30th, 2018 at 11:57 am

It would be good to see real data (published peer-reviewed) on this.

Judith Gottesman on March 30th, 2018 at 12:26 pm

Thank you for this informative article, and for pointing out that humans are the biggest threat to birds and other wildlife, not crows and ravens. People keep selecting which animals they like and then wanting to destroy the ones they find messy, loud, annoying, like crows and seagulls.

Leha Carpenter on March 30th, 2018 at 2:05 pm

Thank you, Adrian Clark, for this article.

Anne B. Clark, Binghamton University, and Kevin McGowan, Cornell Lab of Ornithology discuss findings from North American studies on crows and nest predation in this video about crows. If you want to skip ahead to the part about nest predation, it starts at around 10:47. Kevin McGowan (the speaker here) is America’s top authority on crow research.

https://www.youtube.com/watch?v=I_mlMJLUcTs

(Spoiler alert and fun fact: In North America, ants eat more baby birds than crows do.)

Leha Carpenter on March 30th, 2018 at 2:07 pm

D’oh! Where did I get “Clark” from??? Thank you, Adrian Cotter!

Erin Barca on March 30th, 2018 at 4:14 pm

Thank you, Adrian Cotter.

Yes, they are returning. Thank you for saying this. On a complementary note, has anyone reading this ever seen or heard the throngs of ravens and crows at a productive salmon spawning stream in the Great Bear Rainforest? It’s amazing. These are birds being subsidized by the ocean and other predators, non-human predators. I wonder at the terrible depletion and loss of many species in our state, the salmon and steelhead, tule elk, pronghorn, wolves, etc. Can we truly know what the raven and crow population was like before a certain culture of people invaded, shot, poisoned, and trapped nearly every living being in sight? When there used to be salmon and steelhead in every one of our coastal rivers and streams, feeding many, including the riparian forest trees, growing habitat. When waterfowl darkened the skies. When the sea could feed a thriving population of condors and grizzly bears. I try to imagine it frequently, even though it hurts me to do so.

DEAN ALLEN JONES on April 1st, 2018 at 1:23 am

I with Erin Barca on this one. Over and over again early written accounts by European settlers express awe at the sheer abundance of all kinds of life in a world in which the only human “management” was some intentional seasonal burning by some native groups. Back then no one attempted to use extermination to control the corvids or any other species. I realize that we live in a different era and that the Bay Area of those times will never return. I still think that we need to be patient and to study the complex web of life a lot more before arrogantly assuming the role of “balancing” or of “rebalancing” the scales of something that is far larger and far more intricate and far more self sustaining than anything as humans have, so far managed to create.

Cheri Collins on April 1st, 2018 at 4:36 pm

I fed songbirds, mostly house finches, for years. Then, they were replaced by crows. I started reading about crows in hopes of understanding what happened. I learned that crows are everywhere there are humans. And, the more humans, the more crows. Human lifestyles support crow lifestyles, it seems. And Corvids are highly intelligent. Wildlife which stays or moves into densely human populated areas has to learn to live with us. We’re not easy to live with! I think the intelligence of crows is a significant factor re:their returning to and living well in the Bay Area. Think of them as the avian techies?

susan ives on April 2nd, 2018 at 11:18 am

Hi, Surprisingly, no one has mentioned the impacts of agriculture at Pt Reyes National Seashore on bird populations. Beyond the silage mowing in spring that impacts ground-nesting birds the thousands of cattle in the national park, and the mountains of manure they produce attract corvids.
The corvids also prey on protected species like the Snowy Plover. Little is being done to control the impacts to wildlife of dairy and beef cattle at our national park. A planning process for the park is underway, but ranchers have now hired a lobbyist which may short circuit that process by imposing legislation to guarantee ranching at the park without regard for the environmental impacts.

Laura Cunningham on April 6th, 2018 at 7:04 pm

I think there are more crows in the Bay Area. I grew up here since 1968 and since 2010 I have seen a huge increase in crows. I am a birdwatcher and I recall seeing them only occasionally in October over the decades in the East Bay where I grew up. Now when I see flocks of crows everywhere at all times of year in the East Bay. I keep a daily bird log since 1981. I think this is perhaps due to increased subsidy by urbanization, garbage, and agricultural practices. It would be nice to see a few areas like Pt. Reyes National Seashore returned to a more natural state, without agriculture and livestock, to see how the bird diversity responds. These places are increasingly rare. Ravens are native, but increasing in the California desert due to subsidy by open garbage containers and increased urbanization of wildlands. The increased raven population is harming the Federally Threatened desert tortoise: https://www.fws.gov/carlsbad/PalmSprings/DesertTortoise/Raven%20EA%20Final%203-08.pdf

Ron Sykes on April 29th, 2018 at 9:53 am

I live on the southern border of Pleasant Hill. On 4/28/2018 I saw my first Ravens here. Two sitting in a tree and upsetting the crows until they determined they were not hawks or owls. They were very large birds with big powerful beaks. They were not jet black like a crow but with a more brown/black appearance. I was amazed at their size. One and a half to two times the size of a crow. Amazing. Leave nature alone and it takes care of itself. Humans only screw up the balance.

Caroline Warner on July 9th, 2018 at 9:53 pm

Wow I missed the reply on this and so glad to see it and all the comments. For the record I LOVE BIRDS – all of them. My work is protecting and restoring wetland habitat for birds in the Bay Area. My question about crows isn’t a hate question or whatever else so many inferred. I moved to Woodacre in 2006 and had two crows in my back yard. I loved them. They joined a lot of other birds at my feeders and in my complete sanctuary for animals – no cats and all love. The first year the two successfully raised 5 babies (2 different nests) and then there were 7. And so on. I for sure feel partly responsible for their increase – along with another friend/neighbor! But this year it is seriously different. There are two “murders” of crows that dominant the area. There is no more dawn chorus – all you hear is crows. I’ve watched them eat other birds, one even dropped one on my head, and they have a bunch of weird diseases. It feels like a definite biodiversity issue and in earnest I would like to do something about it – besides not be able to feed birds any more.

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