When I visited Australia, I remember walking around my first day seeing lorikeets and other very tropical-looking birds and thinking "Huh, I guess I'm in Gondwanaland now." Little did I did I know, all perching birds even including my own North American ones are actually Australian! This, from a new PNAS study showing that the last common ancestor was 47 MA ago in Australia. Immediate evolutionary just-so thoughts: Australia has a strange and (relative to other continents) low mammal population, which may have allowed for such a radiation within Australia. Neighboring New Zealand had no mammals at all until seven centuries ago, and is famous for its (sadly threatened) bird diversity, as well as its birds filling many roles usually taken by mammals (hence, now being threatened.) As the Earth went through pulses of cooling and drying and Australia moved north and became drier, less forested, and less hospitable for perching birds, this may have given an opportunity and incentive for a diverse bird population to spread to other continents where they hadn't had similar opportunities to get a head-start on mammals. The paper focuses more on known global climactic shifts, such as the cooling in the Oligocene-Miocene transition: "Three rate shifts [i.e. in rate of diversification] appear to have occurred almost simultaneously during the Oligocene-Miocene transition in three different oscine clades on three different continents...[obviously, after the most recent common ancestor had left Australia.]"
Oliveros CH, Field DJ, Ksepka DT, Barker K, Aleixo A, Andersen MJ, Alström P, Benz BW, Braun EL, Braun MJ, Bravo GA, Brumfield RT, Chesser RT, Claramunt S, Cracraft J, Cuervo AM, Derryberry EP, Glenn TC, Harvey MG, Hosner PA, Joseph L, Kimball RT, Mack AL, Miskelly CM, Peterson AT, Robbins MB, Sheldon FH, Silveira LF, Smith BT, White ND, Moyle RG, Faircloth BC. Earth history and the passerine superradiation. PNAS April 16, 2019 116 (16) 7916-7925