Did I say wind? Nope, I said tidal.I'd dispute that's the main issue (although certainly a worthy factor to consider) - assuming you're referring to offshore wind generation.
While the total generation statistics (usually talked about in TwH in a certain calendar period) make pretty reading, the reality as things stand is somewhat different. If you do a production vs. demand analysis on an hour-by-hour basis over the last 24 months, you'll find that you need quite significant dispatchable capacity to cover the shortfalls in generation from renewable sources (and that's true across the UK, not just Scotland). In reality you should do that same analysis on a minute by minute basis at least.
So you then have a choice between having to have enough gas generation, diesel generation to cover the grid as a whole or no power in the shortfall periods. This is why renewables as they stand don't actually work.
However, this is only true until some sort of breakthrough in cheap energy storage happens. That's a proper game changer.
This was 2011, they have moved forward, a bit since then. The issue, is the marine life, e.g. seals, etc..