Hjelmsøya is a 39 km2 mountainous island north of Havøyasund. There are two large nature reserves on the island: Hjelmsøystauren, a large bird cliff in Staurfjellet on the northernmost part of the island, and Hjelmsøysandfjorden a plant and seabird nature reserve with sand dunes surrounded by steeply sloped mountains.
Most of the seabird species breed in the Hjelmsøystauren nature reserve. Hjelmsøya holds the second largest common guillemot colony in Norwegian territory, 12 – 14 000 pairs, despite having been reduced from 120 000 pairs in the 1970’s. Up to 2000 pairs of Brünnich’s guillemot used to breed on the island in the early 90’s, but the colony has diminished and now few birds visit the colony without producing eggs or chicks. The breeding population of kittiwakes has been severely reduced as well, from its peak of 40 000 breeding pairs to approximately 1200 pairs in the year 2016. Now the most numerous species is the atlantic puffin which population has been estimated to exceed 80 000 pairs breeding at Staurfjellet.