As I said, I don't think it's a question of certainty. We never have certainty in science. In the environmental field we're quite used to operating with a degree of uncertainty. But if you don't know if that species even nests there.... The piping plover example was very instructive. There was habitat that looked like perfectly good habitat, but we found they never used it.
On March 10th, 2009. See this statement in context.