Thanks all - looks like I need to revise my price range, but once I have models to check out, I can start seeing if I can use coupons or cashback or ebay to get a nicer pair discounted.

I've noticed that some are actually waterproof, which may be want I want for kayaking.

I do have a zoom lens (480mm) for the camera, but I think it's inadequate watching birds from the couple of times I've tried it.