At minimum you need a breeding pair to keep the population going. That's a whole lot less than 1200, so from that macro perspective, I'd say it's fairly hard to

At minimum you need a breeding pair to keep the population going. That's a whole lot less than 1200, so from that macro perspective, I'd say it's fairly hard to wipe most things out, especially the things that have made it this far, just like it's hard for me to completely get rid of the duckweed that keeps growing in my fish tank. Even if I pluck out all the visible duckweed, there's always one or two in the filter that re-seed the population and within a few days the whole surface is covered again. Most life is a little bit like this, to the point where I don't think it's very improbable for a species to have bottlenecks. For a species to make it, surviving bottlenecks has to be a defining feature, and for the most part we are exposed to species that make it.