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Natural Heritage

The Isle of May stands like a battleship guarding the mouth of the Firth of Forth. The island is 1.5km long by about 0.5km wide, and covers 57 hectares. Geologically, the island is important as a sill of volcanic rock, crossed by a series of faults which have eroded into steep gullies or geos. There are fine rock stacks, arches and caves along the west cliffs.

The spectacular cliffs on its south-west coast, are where huge colonies of seabirds nest in summer, while the lower, rocky coast to the east and north, is where grey seals haul ashore to breed in autumn. In combination, these features have led to the island being designated as a European Special Protection Area for breeding seabirds, and a Special Area of Conservation to protect its seals and the rocky underwater reefs around the island. The importance of the May is amplified by the long history of scientific study of seabirds and seals on the island. This began when the bird observatory was opened on the island in 1934, while studies of sea mammals date back to 1982. The knowledge from these long-term studies is invaluable today in guiding our conservation priorities.


Only 50 years ago there were just a handful of puffins on the Isle of May. Now there are over 45,000 pairs. The first birds originally moved here from more crowded colonies, in particular the Farne Islands. Now they are very much 'our' puffins, with over 90% returning each year. An unmistakable bird with its black back and white underparts, and distinctive black head with large pale cheeks and a tall, flattened, brightly-coloured bill. Its comical appearance is heightened by its red and black eye-markings and bright orange legs. They nest in burrows.


Shags are goose-sized dark long-necked birds similar to cormorants but smaller and generally slimmer with a characteristic steep forehead. In the breeding season adults develop a dark glossy green plumage and prominent recurved crest on the front of their head. In the UK they breed on coastal sites, mainly in the north and west, and over half their population is found at fewer than 10 sites, making them an Amber List species. Shags usually stay within 100-200km of their breeding grounds.

Black Gull

A very large, thick-set black-backed gull, with a powerful beak. Adults are blacker than the smaller lesser black-backed gull. It has a heavy flight and can look quite hunched when perched. It will fight off other gulls and chase them to snatch food. They are probably the biggest predators on the island with some individuals thinking nothing of killing and eating an adult puffin.

Eider Duck

The UK's heaviest duck, and its fastest flying. It is a true seaduck, rarely found away from coasts where its dependence on coastal molluscs for food has brought it into conflict with mussel farmers. Eiders are highly gregarious and usually stay close inshore, riding the swell in a sandy bay or strung out in long lines out beyond the breaking waves. Look out for them as they are well camouflaged and often nest near the paths.

Artic Tern

With its long tail streamers and general shape the Arctic tern deserves the local name of 'sea swallow'. Appearing white with a black cap, it is largely coastal although it can be seen inland on migration. It depends on a healthy marine environment and some colonies have been affected by fish shortages. Arctic terns are the ultimate long distance migrants - summer visitors to the UK and winter visitors to the Antarctic. You will not need to look far for them as they will greet you as you walk up from the harbour during the season

If you visit the Isle of May over the summer you will almost certainly see grey seals. Over 200 stay all year round, lounging on the rocky shores at the north of the island, or bobbing inquisitively in the sea just offshore as the boats go by. The seals seem to be just as interested in watching the people as the visitors are in spotting them. Like many of the seabirds here, the Isle of May's grey seals are heavily reliant on good numbers of sand eels and other small fish to survive. Come autumn and our resident seals are joined by thousands more pregnant females and bulls who arrive to give birth and mate in the safety of the island. There can be some spectacular fights between the huge bulls, competing to mate with the females. Some of them can weigh up to 300kg. As you can imagine with up to 4000 seals this makes the May pretty chaotic. It's one of the main reasons we close the island to visitors at this time of year.


Nesting on the sea cliffs on the east side they have the smallest nesting area of 10cm2. In this tiny space the female must lay a single, enormous egg. If she were a woman she would give birth to an 18lb baby! The egg is pointed at one end, which is thought to make it less likely to roll off the cliff, and the colours and patterns vary dramatically to help the adults identify them among the hundreds on the same ledge. It comes to land only to nest, spending the rest of its life at sea, where it is vulnerable to oil spills. Dark brown and white, not as black as the similar razorbill, it has a 'bridled' form with a white ring round the eye and stripe behind it.


The razorbill is a medium-sized seabird. It is black above and white below. It has a thick black beak which is deep and blunt, unlike the thinner bill of the similar guillemot. Like the guillemot they nest on the cliffs. They like much more space than their cousins and seem to feel safer in a more enclosed nest. Perhaps this is because their eggs are more oval than the pointed guillemot eggs, making them more likely to roll off the cliff. Birds only come to shore to breed, and winter in the northern Atlantic. The future of this species is linked to the health of the marine environment. Fishing nets, pollution and declining fish stocks all threaten the razorbill.




Isle of May

Wildlife Blog