The site comprises a section of the North West coast of St Helena situated to the South West of James Bay within the area of Halftree Hollow. The site extends inland over Ladder Hill. The coast is dominated by arid basltic sea cliffs, rising mainly to between 300 m and 570 m.
See table for key species. There are 10 breeding species of seabirds in St Helena: Bulweria bulwerii, Pelagodroma marina, Oceanodroma castro, Phaethon aethereus, Sula dactylatra, Sula leucogaster, Onychoprion fuscatus, Anous stolidus, Anous minutus and Gygis alba (Prater, 2012). The site supports the largest breeding colony of P. aethereus in St Helena, with 240 individuals present in 2014 (George & Beard, 2014). P. aethereus have a low breeding success at this site with 19% in 2013 and 26% in 2014 (Beard pers. comm. 2015). The breeding colonies of St Helena are at the most southerly breeding range for this species in the Atlantic (Prater, 2012).
Non-bird biodiversity: The seas around St Helena support a small number of Whale Sharks Rhincodon typus from January to May along with resident Pantropical Spotted Dolphins Stenella attenuata and a few bottlenose dolphins Tursiops truncatus (Prater, 2012). Humpback Whales Megaptera novaeangliae calve off the coast from June to December. The waters are regularly used by Hawksbill Eretmochelys imbricata and Green turtles Chelonia mydas (Prater, 2012).
Pressure/threats to key biodiversity
Introduced invasive species have an impact on the breeding success of P. aethereus at this site, notably with feral cat predation being the main cause of death of chicks (Beard pers. comm. 2015). From the excavation and analysis of bone deposits it is clear that a substantial number of seabirds were breeding on the island prior to the introduction of non-native species (Olson, 1975; Lewis, 2008) including three presumed endemic species that are now extinct including a Pterodroma (rupinarum), Bulweria (bifax) and Puffinus (pacificoides) and four extant but extirpated species including Puffinus lherminieri, Fregata minor, Fregata ariel and Pelagodroma marina. Now only the offshore islands, stacks and steep cliffs provide predator-free breeding areas.
BirdLife International (2020) Important Bird Areas factsheet: Ladder Hill. Downloaded from
http://www.birdlife.org on 19/01/2020.