Learning to Fly (Again)

There is a claim that the giant meteor strike that eliminated the dinosaurs also wiped out the flying birds that had evolved from one of their branches (https://www.theguardian.com/environment/2018/may/24/birds-had-to-relearn-flight-after-meteor-that-wiped-out-dinosaurs). This left only flightless, emu-like species that presumably scavenged in the debris until the forests regrew and re-assuming flight became of utility again.