The names read like a list somebody was working through and gave up on: Hirsholm, Græsholm, Tyvholm, Lilleholm, Møgholm, Pikkerholm, Kovsholm, Kølpen, Deget, Hjellen. None of them is large. Only Hirsholm, the biggest, was ever properly lived on, and everything human about the group — the church, the school, the harbour, the light — is concentrated there. The rest are strips of shingle and turf just high enough to keep their feet dry, shaped and reshaped by sand and clay that the currents deposit and take away again. Standing on Hirsholm you can see the whole archipelago at once, which is one way of understanding how small it is.

The crown held these islands until 1583. They passed through private hands after that, and the state took them back in 1883 — under the defence ministry first, transferred to the environment ministry in 2003. In between, people made livings here in ways that no longer exist anywhere. A pilot station opened in 1733 and guided shipping through the Kattegat approaches until it was closed in 1916. Men cut and shipped stone off the holms. The surrounding water was fished hard. A boat harbour was built in 1860, and a ferry link to Frederikshavn began in 1872 — it still runs, about three times a week. As the stone-cutting and the fishing dwindled, so did everything else: by 1921 there were thirty inhabitants left. Hirsholm had kept both a priest and a schoolmaster for three hundred years. The school closed in 1970. One resident remained until the spring of 2024.

The church on Hirsholm is a small half-timbered Renaissance building put up around 1640, and it is improbably still in use — services are held there several times a year for a congregation that has to arrive by boat. The lighthouse came much later: a 27-metre tower erected in 1886, automated in 1996, retiring the last job that genuinely required somebody to live out here year-round. Concrete of a very different vintage is scattered across Hirsholm and Deget. Eight German bunker positions survive from the 1940–45 occupation, including a searchlight battery built in 1944, when this stretch of water mattered a great deal to people who had no interest in the birds.

Hirsholmene has been a scientific nature reserve since 1938, one of the earliest in Denmark, with the marine protections widened in 1981; it joined the Ramsar list in September 1977 as site number 147, covering 3,714 hectares. The bird list is long and emphatically northern. Eider, common scoter and velvet scoter work the water offshore. Kittiwakes, razorbills and guillemots come through, along with divers and grebes, and gulls of nearly every European kind — herring, lesser black-backed, common, great black-backed. The most interesting residents are the least conspicuous. Six to seven hundred pairs of black guillemots nest at the southern end of the main island, small dark seabirds with white wing patches and startling scarlet feet, tucked into crevices and under stones where nothing much can reach them.

For a while the place had a chronicler. Dines Skafte Jespersen, the Danish author best known for the Troldepus children's books, spent time on Hirsholm and wrote a memoir of a year living and working there, titled Himmel, hav og en ø — Sky, Sea and an Island. As an inventory of the local resources, the title is hard to improve on. Around seven thousand people a year make the crossing now. They walk the marked paths on Hirsholm, read the information boards, and look across fifty metres of open water at Græsholm, where they are not going. Deget is the single exception: it can be visited from August through February, once the nesting is finished and the birds have gone.