I have visited these remote islands a number of times with expedition ships, and landed on all four islands. Just.
The group includes Pitcairn Island, Henderson Island, Ducie Atoll and Oeno Atoll.
Pitcairn Island is the only inhabited island in the group. It is the place where many of the Bounty mutineers eventually ended up.
I have visited this island several times. This island is uninhabited by humans. There are several breeding sea birds, but it is the four endemic 'land' birds that draw people here. There is a Henderson Island Rail, a fruit pigeon, a parrot, and a reed warbler.
The landing here are very difficult, there is only a tiny gap through the coral and the landing is onto rock. Even experienced expedition ships do not always manage to land on this island.
Ducie Atoll is another uninhabited island in the Pitcairn Island group. I have landed here several times, although it is a difficult landing. The island is covered in breeding sea birds.
This is the most difficult of the islands to land. I have only managed once. There are many seabirds breeding here.