Skokholm and Grassholm: The Two Islands You Can't Just Turn Up To

Skomer and Caldey take day visitors. These two don't, really — and that's most of what you need to know before planning around them.

Skokholm

Skokholm lies south of Skomer, off the same stretch of coast. It's smaller, lower and made of old red sandstone, so where Skomer is grey and green, Skokholm is reddish — visibly a different island from the mainland cliffs.

Its claim is historic. Britain's first bird observatory was established here in 1933, by Ronald Lockley, who farmed the island and wrote about it. Migration has been recorded here for the best part of a century, which makes the dataset as much a part of the place as the birds.

The island is managed by the Wildlife Trust of South and West Wales, and the way people visit is by staying, usually for several nights, in restored farm buildings. Occasional day landings happen, but they are the exception rather than something you can plan a holiday around, and stays are booked a long way ahead.

If you can get on, the reason to go is the night. Skokholm has large colonies of Manx shearwaters and storm petrels, and both are nocturnal on land. After dark the whole island fills with noise — shearwaters crash-landing in the dark and calling from underground. Day visitors to any of these islands never experience it. That is the argument for the multi-night stay.

Expect basic, sociable accommodation, a landing that involves a climb, and a crossing that can strand you for a day at either end. That last point is not a hypothetical: getting off on schedule is weather-dependent, and people do get held.

Check the Wildlife Trust's own booking pages for what's available in a given season. Seasons, availability and costs change annually.

Grassholm

Grassholm is about eleven miles out from the mainland, and on a summer day it looks like someone has painted it white.

It holds one of the largest northern gannet colonies in the world — tens of thousands of pairs on a bare rock with no shelter and no soil to speak of. The birds coat it. RSPB owns the island and there is no landing: it's closed to visitors, which is the right call, and the way to see it is on an around-the-island boat trip from the mainland.

Those trips are worth doing. Gannets fish miles from the colony, so you're usually in among diving birds long before you reach the rock, and the last stretch has a constant two-way traffic of birds heading out and back. Downwind, you smell it before you get there. That is not a complaint — it's part of the experience, and everyone who has been mentions it.

Plastic in the nests is a known problem here: the birds collect discarded netting and rope from the sea and weave it in. Wardens deal with the worst of it. It's a good thing to know before you look, because once you've seen it you can't unsee it.

Seeing both without landing

Non-landing trips run out from the same harbours as the island boats, most often from Martin's Haven near Marloes and from St Justinian's near St Davids. They circle, they don't land, and they run in some conditions where a landing is impossible.

Everything here depends on sea state rather than sunshine, and the offshore trips are the first to be cancelled. Book direct, keep a spare day, and read the operator's own conditions.

More on the rest of them in the islands overview and the boat trips guide.