To clarify: what Mann suggests in 1491 is that the disappearance of Native American populations (almost entirely due to epidemic diseases introduced by Europeans) led to a spike in Passenger Pigeon population. So the incredible numbers reported could be accurate despite the lack of evidence that such numbers had been present in the past.
Good observation. The closest modern cognate to the Passenger Pigeon ( at least in numbers ) is probably the Red-Billed Quelea. A smaller bird that doesn’t congregate in quite the mind-bending flocks of the pigeon, but still impressively super-abundant and can be found locally in massive numbers.
Probably. Damned if I’d know where it is, though.
The thing is, nobody takes pictures of things they have seen often before. Weird and odd as the “rivers of birds” thing sounds today, it was a commonplace, and didn’t get articles written about it, or segments on the Nightly News (the way the swarming of Monarch butterflies does)
The link brings up a very good question. Once the population had been reduced into the thousands, what killed the rest of them? Hunting birds in flocks that darken the sky is easy, but hunters aren’t going to track them down one by one. Environmental changes must have killed them off in the end, and from some of the responses here possibly could have been more responsible for their demise than the mass hunting.
It’s quite difficult to photograph or videotape such a phenomenon in such a way that you would get the full effect of it. You can really only photograph as small section of such a flock, unless you have an extreme wide angle lens - and with such a lens each individual bird will appear very tiny. You really can’t get the effect except in person (based on my observations of migratory raptor flocks numbering in the hundreds of thousands).
One idea is that the pigeons virtually required large colonies in order to breed. Once they had been reduced to small scattered flocks they didn’t have the kind of behavioral feedback that they needed to breed successfully.
No cite, but the answer I’ve heard is that, once the population got below a certain critical point, there just weren’t enough birds left for the rest of them to act and breed normally. They had evolved to be part of this giant social mass and the remainders didn’t migrate together when they should have, seek breeding partners, etc because they didn’t have the quantities of birds around them doing the same.
I remember this too. The river of birds (blackbirds of some kind, I think, though that’s just a guess) would continue for an extended period of time back in the 1960s, at least 20 to 30 minutes, probably more. It very much did suggest a river with well-defined banks but a poorly-defined end, as stragglers in their smaller groups of thousands and hundreds would continue for some time after the main group had passed. In the 1970s these flocks, though still massive, were much smaller, and I haven’t seen them since then. It was a wonderful sight, as long as you were not actually standing under the path of the flock.
These things make sense. I can see hunters continue to go after the large flocks until they are greatly reduced in size. There could be a hundred thousand birds left in smaller groups, but not enough in one place to resume their traditional behavior.
Also recommend Farley Mowat’s “Sea of Slaughter” about the abundant wildlife before the settlers arrived. Has numerous cites from journals of the times.