Albatrosses are large, long-billed seabirds related to the petrels, with the "tubenose" bill characteristic of the order. The largest species have the longest wingspans of any extant birds, and they are among the longest-lived of birds. They nest colonially and mate for life. Many species are endangered by pollution, predation of their young by introduced mammals, and as bycatch in long-line fishing activities. They are mainly found in the southern hemisphere but their superbly efficient flight techniques mean that some species can be encountered as vagrants at more northerly latitudes.