Phorusrhacids killing large mammals in National Geographic Channel

[Augusto Haro <augustoharo@gmail.com>]

Last night I was watching a show at Nat Geo with phorusrhacids killing
mammals larger than themselves like Woody Woodpecker, hitting with
their beak, and apparently the downcurved tip of the upper jaw (as a
sidenote, one also put a wolf to sleep with a karate kick on the
head). As far as I know, no Recent bird uses the curved tip of the
upper jaw in this way, but it helps tearing flesh from corpses. In the
show it is also said that the beak is largely hollow... would not this
make the beak more fragile, and thus less likely to perform such
blows?

Is there a recent study suggesting phorusrhacids hitted the prey with
their beaks instead of just biting?