I considered myself a climber (rock and mountain) for thirty years and there are lots of crags with restrictions due to nesting birds. Inland it’s usually Peregrine Falcons and Ravens, coastal crags it’s a whole range of birds. There’s a slight difference to the Snowdon Agreement in that there’s legislation about disturbing nests behind the restrictions and you can be liable for big fines.
In North Wales the main restriction is on the South Stack cliffs at Gogarth near Holyhead with no climbing until the first of August (IIRC). But then why would you want to climb past hundreds of puking fulmars chicks? (if you get fulmar vomit on your clothing then basically it goes straight in the bin!)
As an aside, I wrote one of the climbing guides to the area and happened to have conversations with Iolo Williams (he from Springwatch) about which crags should and shouldn’t have restrictions. It wasn’t “Oh, we’ll ban climbing on …” but “There’s no need for that restriction any more but there’s X starting to nest on …” so it was a fluid situation.
As @cookeaa says, why try and ride on Snowdon when the paths are teeming with walkers? It’s the highest mountain in the UK south of the border and a honey pot. It’s not even that pleasant walking it at the weekend and when I lived there I’d only head up mid-week or on an evening.
