Yesterday I got an email from the USA;
Hello, Mr. Avery. My name is ***********[girl’s name] and I’m a 9th grader at ********** North Junior High. I am doing a class project on passenger pigeons, and I see that you have quite a bit of expertise on the subject. A lot of people have varying opinions on the topic of passenger pigeons. I am curious to know what you think about certain things.
Here are the questions and my answers:
Do you think that passenger pigeons would be able to survive in North America today? Why or why not?
That’s a good question and the answer is yes and no. I think there are plenty of nest sites, and plenty of food for them, but I think we would have to get from zero Passenger Pigeons to millions and millions of them before they would survive and prosper. And that’s because I think that they depended on living in huge flocks, and particularly nesting in huge colonies, to swamp the impacts of predators. When a massive flock of Passenger Pigeons set up a colony in Minnesota then lots would die from predation by hawks, squirrels, bears etc etc but although it was a very large number it was probably a very small proportion because the colony was so huge that local predators could only dent its numbers. So yes, in theory because there’s plenty of food and nest sites, but no in practice because they’d be wiped out easily by predators.
Why do you think passenger pigeons went extinct?
We cut down lots of their forests and we shot/trapped lots of them for food – and none of that can have helped them. But those things, I think, weren’t big enough factors to wipe them out. I think they went extinct because they could no longer swamp the impacts of predators (as above). But it’s a bit of a guess.
What do you think the world would be like today if passenger pigeons were still alive?
Amazing, if they were numerous. I’d love to fly back to the USA and see a Passenger Pigeon colony or winter roost. I’d love to stand and look upwards and see a river of birds flow over my head for hours at a time. And they’d be on TV a lot. They might be a bit of a hazard around airports sometimes though.
How did the extinction of passenger pigeons affect the United States and Canada?
It must have been in quite a big way because over 100 years after the last Passenger Pigeon died in Cincinnati Zoo, Ohio, we are still talking about them. I don’t think the ecology of the USA has changed much – the relative abundance of some trees may have shifted in the absence of Passenger Pigeons eating their acorns but not hugely.
How did the extinction of passenger pigeons affect their ecosystem?
See above – not hugely.
How many passenger pigeons once lived in the wild?
People differ on this – and it’s very difficult to tell. If I had one trip on a time machine I’d like to go back and find out. My guess is about 10 billion – others say fewer, but that’s my guess.
How would reintroducing passenger pigeons to the wild today affect the ecosystem?
Not very much, but it would be very difficult, I think, because one would aim to reintroduce millions, not just a few birds.
How would reintroducing passenger pigeons to the wild affect people?
If they became really numerous again there would be gains and losses for people. They would be pests of crops in some places, I guess. They would be an air safety hazard. But they would be a natural spectacle that would be seen by tens of millions of Americans each year. And they apparently were good to eat.
If they were still alive today, how would climate change affect passenger pigeons? Would they feel the effects of it yet?
Good question! I don’t know but I guess there would be many impacts. They would probably nest a week or two earlier because snow clearance would occur earlier. Maybe they would migrate less far south and spend more time hoovering up beech mast and acorns. Very good question.
What can we learn from the extinction of passenger pigeons to prevent something like it from happening again?
We should learn that when we lose a species we don’t gain much, so it would be better if we found a way to conserve species. We look like idiots if we wipe out species with no benefit to our own species. How daft is that?
I get quite a lot of requests for help a bit like this one. I aim to answer all of them but I don’t always get round to it – sorry! And not all of them are so well expressed as this one so I felt quite highly motivated to answer this young lady’s questions. And so it took some time. And so the blog that I might have written didn’t get done. So I am showing you my homework instead.
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Nice plus heartening. A US 9th Grader — that makes her 14?
murray – yes, 14-15. I was impressed.
Mark, thank-you for so willingly sharing your knowledge with people like this. You’ve probably inspired her to go on and make a positive change in the world.
C – I felt inspired by her questions and interest. I am in the phase of my life when I am not completely useless and one of the things I can do is put something back so that’s what I try to do. However, I do get a lot of requests, almost all completely out of the blue from people I’ve never heard of or met, and some get ignored either because they are too pushy, or daft questions or I mean to reply but get overtaken by other things. So, I’m no saint!
Magic when you get interest like this from ‘the youngsters’. Thirty years ago when I was on a kerbside recycling project we were by far the highest profile environmental project locally so at a time when the environment was the leading issue of the day local school kids would write to us wanting to know more not just about waste issues, but the ozone layer, protecting turtles etc. We would get letters from kids in low income/disadvantaged areas who wanted to know more about rain forests – it’s lack of encouragement of the young especially, not inherent flaws, that mean such areas are often dominated by litter and apathy. There was a bloody big moral obligation to respond – but it was also a huge honour and pleasure to do so. The way that campaigning has gone the past fifteen or so years I feel we’ve largely lost that and I can’t express how much that saddens and frustrates me.
A wee point about the passenger pigeon and its perceived need to exist in very large numbers – I recall reading a reference in this book https://www.amazon.com/Ancient-Americans-Rewriting-History-World/dp/1862076170 a good few years ago that there was evidence that it was human caused changes in the landscape that led to its population explosion, in the older archaeological record its remains are very rare it claimed. I have absolutely no idea how valid the remarks were and if I still had the book would look up the specific reference and source, but I’m afraid I can’t. I know that there’s an argument the American bison became so numerous is because of the virtual extinction of all other terrestrial megafauna approx 12,000 years ago. It could of course be complete guff about the PP, but even then worthwhile to know the idea is being postulated (sort of) publicly somewhere? The fact that a girl from the USA considers an English fellah the go to authority about the PP is quite an accolade – Dr Mark Ian Avery…he’s not just about hen harriers!
Les – yes, I’ve heard some of that stuff about Passenger Pigeons but am not convinced. The archeological record might not be a very good place to look for evidence for a bird with the ecology of the Passenger Pigeon for one thing. But this was a bird that seemed very dependent on old growth deciduous forest and the main thing we did to that was cut it down. PPs might werll have fluctuated a lot in numbers in the past but it is difficult to explain the decline from most numerous bird on the planet to extinct in the wild in a 50 year period without coming up with some factor that operated more strongly when the bird became rarer. But there is a book on the subject, and others have written books apart from mine of course.
This is going to get daft and off topic but here are two irresistible PP quotes:
… It is extremely interesting to see flock after flock [of Passenger Pigeons] performing exactly the same evolutions which have been traced as it were in the air by the preceding flock. Thus should a hawk have charged on a group at a certain spot, the angles, curves and undulations that have been described by the birds … are undeviatingly followed by the next group that comes up.
[John Audubon in 1813, ref.: pp 66-7, A Message from Martha]
And then this:
“… I have seen them [Passenger Pigeons] move in one unbroken column for hours across the sky, like some great river, ever varying in hue; and as the mighty stream, sweeping on at sixty miles an hour, reached some deep valley, it would pour its living mass headlong down hundreds of feet, sounding as though a whirlwind was abroad in the land. I have stood by the grandest waterfall of America and regarded the descending torrents in wonder and astonishment, yet never have my astonishment, wonder, and admiration been so stirred as when I have witnessed these birds drop from their course like meteors from heaven.”
[Simon Pokagon, the 19th Century Potawatami Indian chief and naturalist with one of his famous accounts of the bird’s flocking behaviour, ref.: http://www.birdwatchingdaily.com/featured-stories/like-meteors-heaven/ ]
It’s another one of those daft questions: Can what Audubon saw be explained by super-olfaction – the birds are following the preceding flock’s ‘aerial scent trail’? Or, is it more likely they are using acute vision to follow clouds of dust particles and small feathers shed by the sudden twists and turns of a mass panic escape from mortal danger?
Whatever the cause, was this seemingly useless following behaviour (others have seen it) a consequence of a fundamental adaptation – a highly efficient ability for flocks to find one another and quickly achieve a critical mass of numbers for successful breeding or safe winter roosting? And re Pokogan’s poetic observation, was he witnessing those pigeons finding the scent of a super-mast harvest?
Thanks – I hadn’t heard that contention before or since so it stuck in my mind, but it is difficult to see how a bird with such highly advanced flocking behaviour could exist as other birds do. What an utter phenomenon we’ve lost.
Yes, what was it that made this species become, as Mark puts it in A Message from Martha: ‘a biological storm’ – ‘a unique biological phenomenon’?
How did the Passenger Pigeon generate and sustain such unimaginable abundance when its main food supply was the intermittent tree ‘mast’ crop of the American chestnut, beech and oak? How did the bird keep locating a succession of super-abundant mast areas scattered unevenly and randomly throughout its home range of temperate deciduous forest of eastern North America? To put it another way, how did such huge flocks avoid wasting vital time and energy searching unproductive swathes of that sylvan vastness before locating worthwhile areas to forage en masse? Huge mysteries allow for bonkers contentions like super-olfaction.
But it’s not completely daft:
Tim Birkhead in Chapter 5 in Bird Sense, mentions Floriano Papi’s 1970’s discovery of the ‘olfactory landscape’ which has been found to be an additional way of navigating in homing pigeons. Also discussed, is the sequel to this idea, Gaby Nevitt’s ‘olfactory seascape’ which enables albatrosses and petrels to smell pelagic prey and offal well beyond the horizon.
Mark’s and Tim’s books open the imagination to the possibility of a pre-Columbus, old-growth, pristine forest acting like Nevitt’s ‘olfactory seascape’ – a sea of trees – emitting plumes of volatile compounds which helped a highly adapted Passenger Pigeon to scent-read the forest and locate the largest, densest mast areas.
The more efficiently such an olfactory map could be read (and be memorised from the preceding autumn), the more efficient the spring-time relocation of those crucial mass prospective nesting sites surrounded by an abundance of mast big enough to sustain millions of pairs of breeding pigeons.
The mapping of PP DNA (in progress) may eventually show one way or another if this bird had super-olfaction like Nevitt’s albatrosses.
A very interesting theory Murray!
Exactly Les, I recently had cause to examine the egg of an
Eskimo Curlew, that made me think I can tell you.
When they are gone, that’s it.