AbstractData about breeding populations of birds in the Antarctica are rare and fragmented. Thus, information about the status of the breeding populations of Antarctic birds is crucial given the current scenario of climate change, which is particularly acute in Antarctica. This paper presents new information about the populations of the Antarctic ternSterna vittata, the kelp gullLarus dominicanus, the southern giant petrelMacronectes giganteus, the Antarctic skuaCatharacta antarctica lonnbergi, the chinstrap penguinPygoscelis antarcticaand the gentoo penguinPygoscelis papuaon Byers Peninsula (Livingston Island, South Shetland Islands). We used line transects counts to estimate both densities and numbers of nests of the different species. We estimate that there are 398.96 birds km-2of southern giant petrels (2793 individuals), 62.4 birds km-2of Antarctic tern (3746 individuals) and 269.1 birds km-2of kelp gull (1884 individuals). Furthermore, we found 15 nests of Antarctic skua in 25 km2, from which we can estimate that 60–91 birds must breed on Byers Peninsula. We also censused two colonies of gentoo penguins (3000 and 1200 pairs) and 50 pairs of chinstrap. Compared to previous estimates, gentoo penguins seem to have increased whereas chinstrap penguin have decreased. Finally, the populations of Antarctic tern, southern giant petrel and kelp gull have stabilized or slightly increased.