What is the name of the bird which feeds on penguin blood and meat in Tristan island?
You almost certainly mean the Tristan Thrush, Turdus eremita, which is endemic to Tristan da Cunha. The species is considered to be an opportunistic omnivorous scavenger, but their diet includes the eggs and chicks of many seabird species, as well as the adults of some smaller seabird species.

The Wikipedia page for the species mentions that Tristan Thrush has been recorded drinking penguin blood, citing a BBC documentary which I don't have access to. Five species of penguin have been recorded on Tristan da Cunha, but only the Northern Rockhopper Penguin breeds there (the others are rare visitors to the island). Given the nature of penguin colonies (i.e., densely-packed, and with abundant chicks as well as occasional sick adults), there would be many opportunities for an opportunistic omnivorous scavenger to eat penguin blood, chicks, eggs, or carrion.