Second Passage Island, by far the largest of this group, is over 5.6 miles (9 km) from east to west and up to 1.2 miles (2 km) wide. There are cliffs up to 30 m high of very unstable decaying rock strata around most of the coast. The highest point is Sixtus Hill at 75 m in the eastern half of the island. A small sheltered bay provides the only safe landing near the centre of the northern coast. There is considerable ‘black ground’ above the cliffs and especially behind the old woolshed at the northern inlet where the valley is full of decomposed peat dust, indicating that much of the vegetation has been over-grazed in the past. Tussac is restricted to steep rocky slopes, the western point and the cliffs along the northern shore. There are several ponds, some of which are seasonal and shallow but one, with thriving vegetation, provides feeding grounds for wading birds and waterfowl. Third and Fourth Passage Islands are just 800 m apart and both are low lying, rising to just over 30 m. They are covered with dense Tussac, except for a coastal strip on Fourth Passage and a central area of grassland on Third Passage Island. Both islands were stocked briefly with cattle during the 1960s; since then they have been ungrazed. All three islands are free of introduced predators.
On Second Passage Island, 32 species were recorded in November 1997. Of these, 28 probably breed, including all the resident songbirds except the Falkland Pipit. Six pairs of Striated Caracaras and one pair of Ruddy-headed Geese were recorded but do not qualify the site. The primary importance of this group of islands is the large breeding population of Southern Giant Petrels on Third Passage Island, though the exact size of the colony is unknown. There is a possibility that Third and Fourth Passage Islands support breeding populations of Thin-billed Prions, though this has yet to be confirmed.
Non-bird biodiversity: Six adult Southern Sea Lions were noted on Second Passage Island during the 2003 census, and Third Passage Island held a total of 80 Southern Sea Lions, which included 30 pups. A total of 30 species of flowering plants was recorded on Second Passage Island in November 1997, including both endemic ragworts, Coastal Nassauvia Nassauvia gaudichaudii and Lady’s Slipper Calceolaria fothergillii. Despite being heavily grazed, there were only three species of introduced plants, possibly because the island lies to the west of West Falkland.
BirdLife International (2020) Important Bird Areas factsheet: Passage Islands Group. Downloaded from http://www.birdlife.org on 14/08/2020.