What has happened as a result of already lost migrations, like the passenger pigeon or the bison?
I don’t think we know what the impacts were because there weren’t ecologists around to study these phenomena when they were at their glory. In the intervening years, enough other things have changed to make it difficult to deduce what changes could be attributed to the migration. But it is inconceivable to me that the loss of the most abundant bird on the face of the earth and the greatest mammal migration did not profoundly change the ecosystem. What are the most unappreciated migrations? Most of us fail to appreciate just how many species are migratory. We think about birds but we overlook everything from salamanders to bighorn sheep. For all the major groups of animals, there are a significant number who migrate. It’s a very common strategy. And the most endangered? Clearly, there are endangered species who migrate and by definition those are endangered migrations. But the one that springs to mind is the monarch butterfly. It is still abundant. Yet, all the monarchs of eastern North
