Winter Crow Invasion!

Do you have a metric tonne of crows flooding into your neighborhood/town/city each night?  Do you feel like the crow population is getting out of control?  Are you worried that Alfred Hitchcock’s “The Birds” is about to be a reality?  Do not fear!  What you are experiencing is perfectly normal winter behavior for crows!  In this post we will discuss ROOSTS!

Thousands of crows coming in to roost for the night.

What is a roost?

A roost is a place where birds sleep.  In the context of crows, a roost usually consists of many birds gathering in one location, at dusk, to sleep for the night.  In the winter American crows (Corvus brachyrhynchos) in particular gather in the hundreds to thousands to even millions, in some exceptional cases, each evening.  It’s quite a sight to see and might be a bit disturbing for anyone unfamiliar with this winter behavior!  However, the behavior is just that, a winter one and is therefore temporary.  Crows form massive roosts from November (at the earliest) to about March, when they go back to their home territories to start the nest-building and breeding process.

Why do they gather in such large roosts?

We don’t know for sure, but it’s something American crows have done forever.   One hypothesis as to why they gather like this in winter, is for safety.  One of the main predators for American crows is the great-horned owl.  With longer nights in the winter, having a large group to sleep with after dark might help your chances of not being attacked by an owl.  Having so many other birds means there’s a greater chance it will be a different individual that gets attacked, and also means you have more birds that can detect a predator and send up the alarm to everyone else.  Other hypotheses involve possible information exchange, about foraging sites, but it hasn’t been studied in crows, and many crows just return to their home territories during the day.  It could be that visiting crows (that may have migrated from the north, for the winter) might find out about good foraging sites, but it’s probably not a large contributing factor to roosting behavior.  Finally, roost sites may be conveniently close to good foraging sites, and therefore a good place to sleep.

Crows coming in over an industrial area.

Why do they gather in my town/city?  And not the woods?

I’m sure there are roosts in the woods that people don’t know about, but the biggest conflict with roosts and people are in towns and cities.  Ever parked your car under some trees filled with thousands of birds?  Ever walked under thousands of birds?  Neither the car, nor yourself, likely come out without a fair deal of poop covering you.  Roosts are also quite noisy before the birds all settle down to sleep.  And even then, if they get disturbed in the night, they all sound the alarm, which is quite loud coming from thousands of already-noisy birds!

There are no studies saying exactly why the roosts tend to be in towns, but one hypothesis is that the crows like the light.  Crows see about as well as us humans at night, and the added light might help them spot and evade the dreaded great-horned owl a bit easier.  Great-horned owls are also less abundant in towns.  Urban areas are slightly warmer than rural areas as well, which is an added bonus in the cold winter.  Thirdly, most urban areas prohibit the discharge of firearms, which protects crows from being shot.  Urban areas may also provide better actual sleeping sites, such as taller or specific kinds of trees.

In some cases a roost may have been near a town before the town was even built up, and then the town itself became suitable for roosting (due to the reasons I just gave).  In the case of one roost the Crow Research Group studies, the roost has been documented in the same rough location for over 100 years.  It used to be three miles south of the town, but is now in the middle of downtown, and it likely moved due to the reasons I stated above.

Crows gathered in a group of tall trees.

Doesn’t a roost of so many birds indicate that crows are overpopulated?

No, and there are a couple of reasons why.  Remember that I said crows have been doing this forever?  Well, even if there were only 10 crows in a 100-mile radius, they would come together in the winter to roost.  Additionally, some crows migrate.  In the winter here in New York we tend to get migrant birds down from Canada that join our roosts and communal foraging sites.  So the number of crows in a roost is NOT indicative of the population in a particular area.  The roost contains birds from many miles around and possible migrants.  In the case of roosts further north, they may see fewer crows, as many of theirs have taken off to warmer climes for the winter.

There’s a roost in my town or nearby, what should I do??

Go watch them an enjoy yourself!  Seeing such large aggregations of birds is thrilling and you get to see all sorts of great flights, behaviors, and hear a variety of sounds.  It’s quite comical watching crows vie for space on a branch in a particularly over-loaded tree.

I say bring revenue into the town by having a crow festival in the winter!  Do crow-themed foods, crafts, attractions, competitions, etc.!  Make an eco-tourism site and bring in the money as well as educate people about crows and how wonderful they are!

Is there current research on roosts?

Glad you asked!  The Crow Research Group is trying to get some funding via Experiment.com (crowd-sourcing) to do some movement and roost research!  My colleague, Ben Eisenkop, is interested in how these large roosts affect nitrogen cycling in local environments (since crow poop is chock full of nitrogen).  If you would like to contribute, please click the following link! (The fund raising is over, but please still visit the link to learn more about crow roost research!)

What are the patterns and effects of American crow movements?

29 thoughts on “Winter Crow Invasion!

  1. ChasCPeterson

    Good article! I’ve seen some crow roosts (I used to be married to CL Caffrey): one at the Trenton NJ train station, and a couple in Oklahoma (roosts out in the woods that we do know about).
    Tip: if you can camp yourself under a roost tree before dusk and stay still and quiet enough until crows come in and settle down for the night, you will hear the MOST amazing sounds! Soft and gentle ‘talking’ that is very, very different from the usual raucous caws.

  2. cataranea

    I have always been interested in the fidelity of crows to their foraging sites as they fly out from their roosts. In Vancouver the flights are so massive that it is hard not to speculate about their habits. When they arrive in the morning, some just drop out of the sky from the big stream passing overhead and start foraging immediately. I wonder if they are taking up exactly where they left off the previous evening.

  3. Markus

    Thanks Jen, greatly informative. I live within a few hundred feet of the Saco river, in Maine. Lots of big pine and corn fields. There must be a roost nearby because I have seen hundreds ( I loose count after the first 200 or so ) of crows, in long procession, each November for a few years now. It is an amazing sight and makes me feel insignificant as a human, witnessing this ancient ritual.

  4. Pam

    Thanks for the info. I’ve jokingly wondered to myself about the “crow trees” that I see in the evenings at the subway station when I am going home!!

  5. Lars

    Interesting reading this – Ernest Thompson Seton described a giant crow roost in a Toronto ravine in one of the stories in his “Wild Animals I Have Known”. At the time he was writing, the roost was in the countryside; when I read the story, the site had been surrounded by the city and wasn’t used much by crows anymore.

    Crows here (Calgary) only gather in these big communal roosts in the Fall; then they all fly off and we don’t see them until the Spring. Is this common, crows vacating an area for the Winter? I have no idea where they go.

  6. The Corvid Blog Post author

    Your crows are probably migrating south for the winter. Here in New York, we get Canadian crows for the winter. Calgary winters may be just too harsh for them 🙂

  7. lee

    Very interesting read I saw a roost in Ottawa ontario last year and never seen it before it’s a spectacular sight. I was telling my brother about it and got curious why this happens. Thank you for the information.

  8. Polly Goodfriend Swan

    I live in upstate NY and every late fall, millions of crows come from everywhere to roost in this town . I love watching and listening to them ! but my family is the only ones that do ! the city council spends hundreds of dollars to try and chase them out of town every year ! It is terrible . They use explosives , guns and lazer lights . They even kill some , they are planning a big kill this year . it makes me sick ! my family is the only nature lovers a nd non hunters . If any study is being done on this problem ,please come here to this town and help talk to the city council . I dread winter now because of the hazing of the crows , I wish someone would know how to make this town not the major roost for the entire northern NY area .

  9. Georgia Smith

    Just saw my 1st Crow Roost. I ran to the site with the enthusiasm of a child to see approximately 100 crows. I will go back tonight and quietly listen.
    Thank-you for the above information, now I understand!!!

  10. Hex

    Every year around winter/fall I see bands of crows crossing the sky for what I expect is hours at a time. Ottawa’s probably too cold for them to stay all winter, but I suspect they’re going South and resting for the night, as they often perch in the small woods near my parents’ house. I’ve always loved crows (thanks to reading plenty of animal-protagonist fiction as a kid) so it was always a source of happiness rather than fright for me! I love the idea of a crow festival or something to educate others.

  11. Bob

    Thanks for the blog and information. I live in Little Falls NY and noticed that we have a Humongeous roost of winter crows. I would guess that the numbers are 500 to 1000, maybe more. They are very cool and they provide a great morning alarm clock.

  12. Lyn Ayre

    I heard a crow fly over our house at 11:00 pm, crowing all the way. This really startled me as I thought that once in their roosts, they didn’t go flying for the night. Anyone have any info on this? Thanks for the great article. Warmly Lyn lynayre@telus.net

  13. teresa

    Wow, so glad to hear it’s just a “” winter” ritual,i live in Summerside, prince Edward Island, and I cannot believe the crows that gather at dusk, in the nearby cemetery seems to be a fav spot

  14. The Corvid Blog Post author

    Hi Lyn,

    Crows so not like flying at night, but of a predator disturbs them, they will flee. Sounds like this bird may have been attacked by or avoiding a predator, especially if it was calling the whole time.

  15. The Corvid Blog Post author

    I’m wondering if you live in Auburn? We do actively study that roost. I’m afraid I personally don’t have much political sway as far as stopping the hazing, but I do know my colleagues have tried various discussions and solutions. I remember a couple years back, near Watkins Glenn, on a day they were doing a crow shoot, some folks had us come up and do a crow appreciation day at the same time, including talks and selling crow chocolate bars.

  16. Lisa

    Thanks for the great article! We were watching a solitary crow and I got to searcing for images of crow roosts like the one I saw in commutting from the Trenton NJ train station back in the early 2000s. My husband and found your page this way. Its so amazing to see thousands of birrds move, talk, and interract in one location!

  17. ceydonia

    I had the luck of catching a temporary roost of a “super flock” (that’s what I had always heard it called) in Manchester, NH about 20 years ago. It was late evening in the fall, and all the trees around my apartment looked kind of weird in the half-light. Too dark to make out details, but enough light to see. Turns out that it was more than 1000 crows taking over the (mostly pine) trees in my neighbourhood. It was AMAZING. And yes, I could hear the soft chattering and quiet caws between them. I was in such awe. I have always admired them for their intelligence, but listening to them talk about whatever they were discussing, made me love them. they have a winter roost somewhere near Goffstown, NH, so I get to see them all winter long. Love it.

  18. James T.

    Thanks a whole dang lot ye northerners for all the dang crows we are getting now (in Central FL)! I’d rather it remain quiet like it normally is (I live on an 18 acre Cattle Ranch) & a bunch of people around here have already used their guns to scare them off but apparently it doesn’t work…

  19. Marian Harvey

    Grateful to find you! I’m Granny Crow because I shapeshift to visit Grandson CheLua in Oakland from rural Roachdale, IN where our woods/fields continue to be destroyed by Corporate Agriculture/Right to Farms’ relentless expansion of intense confinement livestock production. I grieve the loss of my Friends, the Birds can’t survive on the chemical laden corn/soy, barren, flattened land…Rural towns and cities, increasingly, are finding ways to “get rid of” Crows…and there was a post, seeking help from Indiana Animal Rights Alliance on Facebook to protect the Crows in Bloomington, Indiana. We’re finally, County by County, protesting Hogwrestling. In the same way, the “Crow problem” permeates our towns and we need to help our Communities to live with, not torment and kill, the wildlife we’ve driven from their homes. If there is any Hoosier Crow lover who might help us organize please contact Indiana Animal Rights Alliance….blessings, thank you Marian Patience “Granny Crow”

  20. BirdLover

    Hi, I live in Northern Toronto Ontario(North York near Wilson/Bathurst) And have always been a fan of these intelligent birds. But, in the past year, I have not seen any crows at all and I wonder where they may have all gone. If anyone has any information, please message. thanx.

  21. jenniesisler

    So that explains the invasion in Springfield, Massachusetts! I was getting rather creeped out by it, even as much as I love birds. Thanks for this information.

  22. tincanification

    i live in a downtown high-rise in Calgary and have witnessed this crow ritual for years. Having worked many night shifts in the downtown area, I have seen them roost on the less taller and older buildings like the old sandstone Court of Appeals, alongside the LRT platform. This twice daily exodus of these murderous avian jokers tends to occur mostly in early fall and late spring here in Calgary [as one other poster mentioned]. I quite enjoyed the piece, cheers and…caw-caw!

  23. Lucy Kemnitzer

    (I did notice this entry is 3 years old) I live in Santa Cruz, California, and our crows roost here all year. Their behavior does seem different in the summer, but it’s not that they don’t form roosts. They seem to form smaller ones more spread out, but not very widespread, so that I still see almost the same number in the neighborhood. (between 65-110 I think) This community of crows is pretty recent, no more than 25 or 30 years old- I remember them arriving but I didn’t make note of the year. It’s a food-rich area with a lot of diversity of land use so maybe that’s why? My neighborhood has a small estuary which is a wildlife refuge, a residential neighborhood with a semi-suburban character, a fishing wharf, an amusement park, some schools, and a restaurant-dense shopping area all in a few blocks. I’ve noticed that the afternoon ritual (which I call a “hullabaloo” because they seem to be performing for each other) shifts so that it is always a couple of hours before dark, with the exception of the early fall when the acorns at the end of the street are ripe, when the hullabaloo goes on all day off and on for several days.

    They also do a thing sometimes where they sit on the wires on my block, by ones and twos but several at a time, where they seem to be watching us and commenting on us. I think that is a summer activity.

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