Origin of birds
A May 2018 report, in Current Biology, says that its authors think that the birds that survived the end-of-Cretaceous disaster were Neornithes, Neognathae (Galloanserae + Neoaves). They were not tree-living, and could not fly far. After the world-wide destruction of forests, it took a long time for the world's forests to return properly. Virtually the same conclusions were already reached before, in a 2017 book on avian evolution.