I would think so too. But most species are capable of switching among multiple food sources, to compensate for lean times. I think this allows those critters

I would think so too. But most species are capable of switching among multiple food sources, to compensate for lean times. I think this allows those critters that are already living to stay alive. But it probably limits their ability to reproduce, since their young are unlikely to be as flexible in finding food. I suspect the impact of a long-term change in foodstuffs will take a while to fully propagate.