Meet the Neighbors: The Crows of the CBRM

Crows fascinate me.

Try as I might not to anthropomorphize them, I catch myself thinking of them as sly or wise or watchful or mocking, depending upon whether they’re emptying my bird feeder, dancing on my roof, poking around my recycling or crapping on my head as I walk down North Charlotte Street of a winter’s evening (I anthropomorphize them, I don’t romanticize them).


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The roost I’m familiar with in the North End of Sydney is one of two in the local area, according to CBU biologist David McCorquodale:

In the Sydney area they often roost in Wash Brook valley (from [the] old incinerator down to the North end) and often there is a roost in Sydney Mines/Florence as well. My estimate is that these roosts have close to 10,000 individuals at the peak during the early winter.

McCorquodale says crows roost from mid-autumn through into April.  Our crows are American Crows or Corvus brachyrhynchos which are considered to be “partially migratory,” meaning some  migrate and some don’t.  McCorquodale says it appears as if most crows in NS now spend the winter in the province. (Insert exchange rate joke here.)

The Cornell Lab of Ornithology  site (a fantastic bird resource) characterizes American crows as:

…very social, sometimes forming flocks in the thousands. Inquisitive and sometimes mischievous, crows are good learners and problem-solvers, often raiding garbage cans and picking over discarded food containers. They’re also aggressive and often chase away larger birds including hawks, owls and herons.

(Add bald eagles to that list, a feat I have witnessed myself. Also, note that scientists use the word “flock” rather than “murder” to describe a group of crows.)


Safety in Numbers

David Harris, formerly of the Nova Scotia Department of Natural Resources (DNR), now retired, says an interesting facet of the North End roost is that it is mobile:

Depending on temperature and wind direction, it moves around the harbor. Sometimes in the North End, sometimes in the Pier, also often in Westmount. When the harbor freezes on quiet evenings, they roost on the ice.

Terry Power, a current DNR employee, says roosting on the ice is primarily for protection from predators, but “could also have some benefits for keeping warm.”

Some of the birds you see perched in the trees at night will have traveled “tens of kilometers” to get there, because roosting together has benefits. Says McCorquodale:

Two key things about the roosts are safety (from cats, raccoons, owls, people) and information sharing. By this I mean, with large numbers of crows, it is almost guaranteed that one will detect the danger and alert the others. Crows learn or glean information about foraging sites and social interactions in the roosts too.

The CBRM flocks are “small potatoes” as crow roosts go. McCorquodale says Nova Scotia is home to similar-sized roosts around Pictou, Truro, Kentville and Mount St. Vincent University in Halifax. (To see just how ubiquitous American Crows are in our region, see the Martimes Breeding Bird Atlas.)

Power said when he lived in the Annapolis Valley in the 1980s, there was a roost on Boot Island (a nature preserve in the Minas Basin off the coast of Grand Pré) that counted between 25,000 and 27,000 birds. Power’s DNR colleagues studied the Boot Island roost throughout the ’80s and found the crows there came from a broad section of the Valley. In foraging for food, he said, they “have to distribute themselves over large areas, especially when you get large numbers of birds.”

But while the Boot Island flock was “phenomenal” for Nova Scotia, crow roosts can contain hundreds of thousands of birds, if not more. One roost in Fort Cobb Oklahoma in 1972 was estimated to hold two million crows.

American crows roosting in tree on the Esplanade, CBRM.

American Crows roosting in a tree on the Esplanade, CBRM.



Wild Party

What really piques my curiosity about the North End crows is the noise they make at dawn, as they head out for the day, and at dusk, as they return to the roost. In an attempt to find out what all the racket is about, I contacted Dr. Kevin McGowan of the Cornell Laboratory of Ornithology, who has been studying the American Crows and Fish Crows of Ithaca, New York, since 1988.

McGowan, who maintains a website dedicated to crows, told me it’s “really difficult to tease apart…what they’re communicating about or why.”

[T]here are lots of …possibilities for what could be going on in a roost. Some of it may be mate-finding, that the young birds that are out there are keeping their eyes open for a cute mate out there among that big flock…

The other is that crows don’t breed until they’re three to five years old and most of the ones who don’t stay home with their parents. So the question is, if you’re a young bird, are you going to go off and try to make your way in the world or not? And these sorts of gatherings — where you’ll see a lot of talking, a lot of chasing, a lot of flying around — those may, in fact, be sort of informational exercises for the young birds to figure out, ‘I think I’m a pretty fast flier but oops, maybe I’m not as fast as I thought I was.’…[S]ome sort of personal assessment that affects later decisions on what you should be doing in life. Those are big wild speculations [laughs].

McGowan’s crow FAQ notes that crows have “lots” of calls but most of them sound like “caw.” Crow language, he told me, is tonal (he compared it to human tonal languages, like Chinese or Vietnamese, which use pitch to give a single word multiple meanings). Where I walk by a roost and hear “caws,” McGowan hears much more:

[W]hat we find in these roosts is there’s just a lot of talk going on and they talk about everything. I mean…almost every single vocalization that I’ve ever heard, you can hear at night in these pre-roost gatherings or in the roost, and a lot of them just don’t make any sense.

Some of them, the sort of standard, regular cawing, is just perhaps a chorus of, ‘Yeah, me too,’ …just sort of keeping the whole social gathering going. And, again, shout out – what’s your voice sound like, relative to everyone else? Am I a baritone or am I a tenor? Do I have an impressive voice or don’t I have an impressive voice?

Those are possibilities for what they do, but they also do alarm calls, and nobody’s alarmed; they do greeting calls; they do all kinds of crazy stuff in there. It’s a wild party. Then all of a sudden they all go quiet then head off to the final spot. It’s pretty interesting to watch.


Life and Times

McGowan’s crow FAQ notes that half of all crows die in the egg or as nestlings. He bands young birds just before they fledge and says roughly half of those he bands are still alive and with their parents a year later ( “a pretty good survival rate” by bird standards).

In terms of life expectancy, McGowan says they’ve had three crows in the population they study live to 19, although most birds, once they become breeders, make it to about 10 years of age. (Crows have the potential to live much longer, though — McGowan says one in captivity is known to have lived over 50 years).

Compared to birds like robins and blue jays, who mature rapidly and breed at one year, crows experience a prolonged adolescence. Says McGowan:

[C]rows aren’t adult until they’re at least two years old and we can see that…The yearlings, they just don’t do things the way the adults do. You know, everybody will go defend the territory and fly up and chase the intruders off and…the yearling just sits there and sings a little bit to himself and picks off a leaf…They’re just not there yet.

As mentioned, some crows will remain with their parents for years, helping raise subsequent generations of young. Power said he thinks that “cooperative” method of raising young benefits parents and offspring alike:

I’m sure that the young help raise the immediate family but the other side of it, those young birds that are hanging around helping are learning how to avoid trouble.

McGowan agrees:

Crows learn a lot during their first year about what to be afraid of and what not to be afraid of, what’s a food source, what do you have to worry about, and they get a lot of that from their parents. It’s not just, ‘Where’s the food?’ and ‘I can find food now,’ but it’s like, ‘Watch out!’ ‘Don’t touch that!’ ‘Look out for that car!’

For birds who don’t remain with their parents, McGowan says the roost may be a source of this sort of education. Crows, it seems, really have each other’s backs. McGowan says when crows warn other crows of danger “it’s like they believe each other.”

They say, ‘Oh, that’s dangerous! That’s a bad person.’ It’s like, ‘Well, what’d he do?’ ‘I don’t know but somebody told me he’s a bad person and I believe him.’ And then that gets transferred down the line, so you’re 10 steps down the line, 10 birds removed from the crow that actually got shot at.

But it’s beneficial for the birds to do that and to be wary. In the natural world, there’s a little bit more of a prize for being a little bit overly cautious than for not being cautious enough. Sure, it’s good not to be too worried, you can get in and get food faster, but potential mistakes are costly, meaning you die.


Crow Hop

McGowan is not at all interested in the mythological significance of crows which is fair enough, he’s a scientist after all.crow_edit_05

But I do love a myth and knowing that crows and ravens figure prominently in First Nations mythology, I asked Eskasoni’s Elizabeth Marshall to tell me something about the crow in Mi’kmaq legend. She said her partner’s last name is Gabriel, and his family of Gabriels is known as the Crow clan, ‘Kaqawej’ in Mi’kmaq.

Better still, the Mi’kmaq have a dance called the “Crow Hop” which Marshall says:

…mimics the crow’s tendency to repeatedly poke its prey with a stick, until the prey grabs the stick which the crow then pops in its mouth..

And now back to our scientific discussion…


Getting to Know You

McGowan, on his website, says crow have “one endearing characteristic that is apparently not shared by other birds.”

They will get to know people as individuals. While you can get chickadees to eat out of your hand, any old hand will do, and I suspect that the chickadees do not know you as an individual. Crows will! If you toss them peanuts (I recommend unsalted, in the shell) on a regular basis, they will wait and watch for you. Not just any person, but you.

By the same token, if you get on their bad side, they’ll remember that too:

[T]hey also are happy to turn this talent of recognition to the darker side, and treat you as an enemy. (Again, not just all people, but YOU.) Because I climb to crow nests to band young birds, many crows in Ithaca know me and hate me. Whenever they notice me in their territory they will come over and yell at me. They will follow me around and keep yelling for as long as I am there…


Stop Making Sense

McGowan says that when you are accustomed to viewing the world through what he calls “the lens” of evolution and natural selection, a lot of bird behavior makes sense:

It’s obvious why a male songbird sings and fights and has bright plumage and all of that, that’s obvious. And it’s obvious why a killdeer will do a distraction play to try to keep a predator away from their eggs.

Such behaviors can be fascinating, he says, but it’s the behaviors that don’t make sense from the point of view of evolution or natural selection that really intrigue him, and he’s seen crows do some very odd things:

I was radio-tracking some crows going to the roost a number of years ago…[T]here was a big pre-roost gathering, there were about 3,000 birds or so…going to go into a roost and they were…chasing back and forth and yelling, and I had a bead on this one kid and was following him as he was moving through the large group.

Then the whole group took off to the south and this kid turned around and went home. He went back to his family on territory and slept on territory that night. So, it’s like he went to the party but didn’t do the sleepover. To that guy, that wasn’t a big, ‘Hey, where are we going to go tonight guys? Where’s the spot?’ There wasn’t any discussion about the future…or what was going to happen tomorrow morning. It was something about the right then and there, and…what I realized is that there’s something about the gathering itself that provides information or something for these birds, whether they follow through with the actual clustering and then dispersal in the morning…We don’t honestly have a good sense of what that could be.

It’s the sort of mystery that might keep a person interested in crows. As McGowan says:

[T]hey’re very interesting birds in a number of ways. There’s just a lot going on. There’s nothing simple about a crow’s life.