Quote:
Originally Posted by Isopod
While I'm certainly not denying the existence of the bucket brigade, all of Alberta except the highest peaks of the Cypress Hills and the Rockies were covered by a couple kilometres of glacial ice until around 10,000 years ago. Somehow after the ice retreated our lakes and rivers became populated by all sorts of fish species, in all sorts of waters. That wasn't done by the bucket brigade, so there is some way that fish can move fairly easily from lake to lake, river to river, and can re-populate a landscape that was under kilometres of ice and devoid of fish to be filled with multiple fish species in most waters, within a fairly short period of time. Birds have to play a role, I can't think what else could do it.
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As the Glaciers retreated, the drainages were different than they are now. Drainages evolved over time but there are still distinct differences in species make up in our current drainage systems... Only grayling south of the Athabasca is in Montana. No sturgeon north of the NSR. Only rainbows in the upper Athabasca...and so on.
Birds did not do it. Access via evolving drainages is the reason.
Cheers
Sun