Superabundant is not a term that biologists toss around lightly. It usually doesn’t apply to bigger vertebrates – flights of geese during migration, swirling schools of fish – since even large groups may involve only a few hundred or a few thousand individuals. It’s more suited to big “blooms” of insects. I’ve seen clouds of Chironomids (nonbiting midges) that seem to be everywhere, and fishflies so thick we had to clear their carcasses away with a shovel. These animals were certainly superabundant, since they numbered in the millions, but each one was tiny.
That’s where the Passenger Pigeon stands out. A sky darkened not by hundreds or thousands, but by millions of large fast-flying birds is one of the more intriguing things about them. The species was common in Saskatchewan, according to historic accounts, and they nested here. But the big nesting colonies occurred in eastern parts of the USA, where unbelievable numbers would fly past for hours or days at a time. In fact, the birds were named because of the way that their flocks would pass by during migration or when they were searching for food. Artists who saw them tried to depict the scene, and the RSM will be giving visitors a sense of it as part of an upcoming exhibit about extinct and threatened species called “A Roar of Wings.” But what does this sort of “superabundance” actually look like?
People living in Germany in the 1700s would have known, but they weren’t thinking about Passenger Pigeons. They were concerned about House Sparrows. On this side of the Atlantic, the House Sparrow is well known as a feisty social bird that was intentionally introduced to this continent in 1852. House Sparrows have never been superabundant here, but in 18th century Europe, as large areas were cleared for farming, their populations exploded. Quick to take advantage of building and crops, House Sparrow numbers got to the point where the species was declared an agricultural pest and people were paid to bring in sparrow heads.
The “sparrow issue” is no longer a problem in Europe, partly because of changes in farming practices, but it has a modern analog in the Red-billed Quelea, a species of weaver bird that is currently an agricultural pest in Africa. The House Sparrow and the Red-billed Quelea are both much smaller than the Passenger Pigeon, but this video [Swarming Red-billed Quelea in Africa] gives some idea of what a sky full of pigeons might have been like.