Real Science Hurts Brains: Crow Edition


Didja know real life is ridiculously complicated?  Even simple things involve a lot, if your observation runs close enough – one classic example of baking a pie from scratch requiring the creation of a universe.  Causes are often multifactorial, because how could they not be?  The pie example runs through the ingredients, the cultivation of apples and wheat and cows to make butter etc., but that pie also needs a human to put it together, who must be educated from societies that had to evolve all the way up from monkey grunting, besides the hundreds of millions of years since we diverged from our last common ancestor with apples, and the billions of years of natural selection running to the two minutes after the Hadean magma cooled.

So I say that if you’re genuinely trying to arrive at the truth of a given thing, you need to wrack your brain for all the considerations, contingencies, and possibilities.  If you wants tha Real Science, you gots ta be willing to come up with a lot more than a single hypothesis.  Yes, to test, you have to narrow things down to the ideas you’re going to test, but to make that test as rigorous as possible, you should really try to think of every possible factor that could confound the results.  Stretch that brain.  Presumably that’s why you went into science, right?  To feel smart?

But no.  It’s easier to feel smart if you blithely whistle past all the ways you could be wrong, like evopsych assholes and scientific racists (how much overlap those fields possess).  One hypothesis.  A few cheesy tests.  Maybe squint and look at the data sideways, and by jove, you’ve cracked it!  Now go get as many women pregnant as possible, to share your genetic genius with the world.

Over here in the real world, you could be like me, and know just enough to be sure you’ll never fully understand anything.  Don’t throw your hands up and veg out watching George Michaels videos on yewchoob until you die.  Stay wondering.  Be frustrated forever by the fact real science hurts, and take your cold solace in the awareness at least you aren’t an evopsych fucko, or qanon, or moon landing truther, etc etc.

Here I come to the actual point of the article.  Does anyone know why crow populations are skyrocketing in the Pacific Northwest?  I could be wrong about this, but to my slightly-less-than-casual observation, they may have doubled or tripled in population within the last few years.  This was well after a documented boom they had back in the late twentieth century.

A possible point of failure in this question:  observational bias.  Most of my travels in a given week range from Auburn to Federal Way and back – up and down the west side of one little valley.  Maybe there are more crows here than elsewhere.  Maybe I had poorer observation of their numbers in previous years because I wasn’t paying as close of attention.  Maybe my mind is exaggerating, and they always gathered by the hundreds on the edge of the mall, sunning themselves in the morning light, in preparation for the daily hustle.  Maybe if I’d been driven down the west end of Main Street before, at the right time of day, I would have already seen them dotting the little lawns and parking lots and rooftops and trees, in groups ranging from dozens to hundreds, block after block.  Maybe they would always gather in megaflocks in the south of Auburn somewhere, making a cacophony that can be heard a mile away.

Sounded like I was trying to convince myself my observations were accurate toward the end of that paragraph, but I absolutely do recognize this perception could be flawed.  It literally could be a matter that I was never in the right place or time of day or time of year to see these crow convocations before.  In which case, there’s no phenomenon to wonder about.  But assuming there is a phenomenon, what’s causing it..?

Here’s where the range of possibilities starts to hurt the brain.  If I was a shit scientist instead of a vexed layperson, I would just cook up one hypothesis and a single test to run for it, then congratulate myself in print and get quoted in popular science magazines.  Instead, I sit here realizing how complex this can be – maybe even unknowable.  Some things I’ve considered:

Food explosion.  I learned from Abe Oceanoxia that invasive European earthworms have taken over the USA in huge numbers, and crows happily eat a lot of worms, whatever their proclivity for french fries.  Maybe earthworms are having a population explosion for reasons I can’t even begin to guess at.  Or maybe they’re just more available, because long years of drought seem to have ended here, and rain drives them to the surfaces of lawns and sidewalks.  Any given rainy day, you’ll see robins and crows both going for the wriggly pink smorgasbord, crows most of all.

Or maybe there’s another food altogether that has increased.  As covid and the ascent of global fascism have fostered a sense of doom in the younger generations, increasing deaths from despair, it has certainly increased the amount of litter.  Is the food explosion mostly human trash?

Predator decline.  I’ve heard that owls are the most prolific predators of crows.  I imagine cats and dogs take their share as well.  Well, we’ve no shortage of cats and dogs, but maybe the species of owl that eats crows has taken a population hit – or altered their behavior based on availability of a different prey animal or animals.

Or maybe a competing predator of the food they eat has experienced a decline, like worms becoming overpopulated due to a mole plague.

Natural selection.  Maybe a disease that had been killing crows had winnowed the population to those crows with a resistance, and those crows in turn had a big population boom?  Maybe crows had only bred at certain times of year to avoid competing with themselves but that was an obsolete limitation and year-long breeding finally won out majority expression in the population?  Maybe something crows eat had an evolutionary breakthrough and exploded.

Cultural selection.  Maybe crows figured out a cool trick they hadn’t done before.  I was once impressed by watching a crow use a tool, but since then have seen it again several times.  What’s interesting is the tool is the same – a short straight stick, just a few inches.  Was the technique of crafting this tool communicated, or were they all learning to go for the same source for the tool, or have I just seen one crow who packs its tool everywhere it goes, and gets around?

I haven’t seen this so often that it could make that big a population difference, but maybe there is some other behavioral trait they’ve increased.  Maybe they mob raptors and ravens so often now that they are being preyed upon less often, or are competing less for food.  Maybe they’ve increased the frequency of the food call.  There’s a tension in crow instincts between the desire to have food all to oneself and the desire to call a bunch of crows in to share.  If they’re all doing the food call more often, they’re eating food before any competing species can get to it.

My husband saw a yewchoob vid where some weirdos left a mound of peanut butter in the woods and crows ate almost all of it, beating out bears and coyotes and raccoons and more, strictly because of this instinct to call in your friends.  Well, that and having less hesitation about strange food sources.  The coyote missed out because he was too scared of the blob to eat it.  Maybe the hesitation recently reduced even more.

Commensalism.  Human population in the region has also exploded.  The town I live in has three times as many people as it did when I first moved here as a child.  More people, more lawns with worms, more fast food places and restaurants producing food waste, more rats and mice and pigeons and starlings to eat.  I’ve seen them eat pigeons and starlings before.  Hell, an increase in predatory behavior could drive population, or even cause an evolutionary split between crows with different feeding habits.

Niche partitioning.  Maybe that last one is it.  Maybe there’s been an invisible split along behavioral lines in food gleaning, which is the beginning of a speciation event that may or may not ever reach completion before it collapses back in on itself due to climate change or other human issues.

Some or all of the above.  The cause is multifactorial after all.

None of the above.  Phenomenon isn’t real.  I’m tripping and all this thought is for nothing.

Hell, all this thought assuredly is for nothing because I will never know the answer, whether it’s knowable or not.  And yet the thoughts still happen.  At least it shows I’m smarter than an evopsych dick.  That’s nice.

Comments

  1. John Morales says

    My husband saw a yewchoob vid where some weirdos left a mound of peanut butter in the woods and crows ate almost all of it, beating out bears and coyotes and raccoons and more, strictly because of this instinct to call in your friends.

    Heh. Cute channel, that one.

  2. flex says

    I can’t say anything about an increase in crows in your area, but I have noticed a decline in birds in general in mine.

    What have I really noticed? Less birdseed eaten at the feeder in the winter.

    I suppose there are a number of possibilities…
    Maybe because the winters have been more mild, they haven’t needed the seed. However, birds seem to be opportunists, and if seed is available I would expect them to find it and empty the feeder.
    Maybe the squirrels were eating more than I thought in previous years. Certainly possible, I don’t have a camera on it to see how often the squirrels get into it. Again, mild winters may put less pressure on squirrels to raid feeders.
    Maybe there really are fewer birds.

    Since I’ve also noticed a decrease in insects in my area over the last few years (aside from ticks, they are moving in), maybe the reduction in the insect population is directly impacting the bird population.

    We do get crows, but they seem to be nesting couples and except for the early spring and late fall when they are moving around we only see 3-4 at a time. We have seen more coopers hawks and heard more owls in the last few summers, so that may be a factor too. The feral cat population is down quite a bit, according to the local humane society. But the coyote and fox population has been increasing.

  3. another stewart says

    To test whether the phenomenon is real, you could look at iNaturalist to see how the number of records has changed over time. (Drawing a circle round Seattle to cover the coastal Pacific NorthWest, including SW BC, gives you 30,000-40,000 records.) You’d want to control for changes in recording intensity, so you’d want to do the same for a control sample of other ecologically similar bird species.

    GBIF has two orders of magnitude more records.

  4. Pierce R. Butler says

    Maybe you should look at it the other way ’round: with the Guardians Of Pedophiles having adopted a creed of never admitting fault or failure, many fewer people are eating crow.

  5. rwiess says

    Observations over my lifetime, aided by a good friend who did his PhD on crow behavior: In the early 70’s we were amazed to see a crow in a park in Seattle who allowed us to approach to about 10 feet away before it flew off. Had never gotten anywhere near that close to a crow before, and rarely saw them in the city. By the late 80’s, crows are everywhere, and we followed the morning and evening gatherings to find the roosts. There were many roosts. (factoid- there were generally roosts of robins in the winter nearby) There were many roosts. In the last 30 years, growth in the city has eliminated many roosts, either direct destruction or just building too much too close. Now the roosts are far fewer, and mostly further north or south of Seattle. Not surprised you are seeing more crows down your way, as that is a major remaining roosts. All the crows are in the roosts in winter. In breeding season the breeders have territories throughout the city, while non-breeders are still in the roosts.

  6. says

    john – dere it iz

    flex – i feel like i’ve seen markedly fewer small backyard birds in the last few years. it’s well-supported that insect populations are diminishing globally, and it could be to blame. are we belatedly heading for rachel carson’s silent spring? i hates it, but even with smaller pops, we still have all the usual suspects out here – especially juncos, chickadees, and bushtits. crows don’t spend as much time in our cul-de-sac as they do elsewhere, and are usually focused on the worms when they’re around. and we do have at least a handful of regular outdoor cats here.

    stew – good to know if i had the sauce for citizen science, there are resources. of course, there have been quite a few papers on crows in the scientific literature as well. they’re easy wild animals to study, good for student work.

    pierce – as much as i don’t mind having lots of crows around, those fuckos need to start chompin’. good for nothins.

    rwiess – my husband found some info on dramatic increases around here since the 1960s, so boomin’ has been going on for a while. he also mentioned roosts in the cities were displaced, with one noted roost in kent. by now there could easily be a big roost in my neighborhood, as many trees as are on the hill just across the river.

    for years we’ve seen crows during commuting hours, commuting along with the people. it’s like they have their own aerial I-5. thousands go north to scavenge and come south to sleep. i bet there are similar routes between other suburban roosts and daytime food sources. this raises a question for me – might they have learned to commute by watching us do it?

    this also raises another possible reason for population increase. if a roost in seattle is driven to the four winds by construction, and each of the separate roosts build their numbers up to pre-split levels, you have four times the crows. repeated disruptions could be causing new roosts to develop all over the region.

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