SV: Phorusrhacids killing large mammals in National Geographic Channel

["Tommy Tyrberg" <tommy.tyrberg@norrkoping.mail.telia.com>]

While it is true that most birds do not habitually kill prey heavier
than about half their weight there are plenty of exceptions. Golden
Eagles regularly kill adult foxes which are about the same weight as an
eagle. Merlins frequently kill birds of nearly their own weight. Pygmy
Owls at least occasionally kill prey considerably heavier than
themselves (e. g. Mistlethrush). These are just examples I can think of
right away, there are undoubtedly many more. 
I think an important factor in prey size is that birds frequently have
to be able to lift and transport the prey. It is certainly quite
possible to train birds to kill much larger prey than they normally do
in the wild. Falconers for example have trained Golden Eagles to kill
wolves, Peregrines and Goshawks to hunt cranes and herons and merlins to
hunt pigeons.
For a large flightless predator like a phorusrhacid I should think
killing prey their own weight would be fairly easy.


Tommy Tyrberg

-----Ursprungligt meddelande-----
Från: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] För Augusto
Haro
Skickat: den 21 juli 2009 20:21
Till: lor@fibertel.com.ar
Kopia: dinosaur
Ämne: Re: Phorusrhacids killing large mammals in National Geographic
Channel

It seems to be that the claws of some phorusrhacids are laterally
compressed instead of wide and blunt as in Ratites, so they are
supposed to use their legs to kick small prey. As far as I know, the
beak is tall and laterally compressed in at least some phorusrhacids.
I suppose perhaps the pointed tip was used more as a canine to kill
with a bite, which would serve for itself against small prey, but not
with prey closer to their size. Unless phorusrhacids shake their heads
to the sides like crocs and dogs, then they may easily kill animals
half their size, but I do not know of birds which do so. Also, the
long pointing tip of the upper jaw and the dorsoventrally tall beak
seems to better suggest resistance to orthal (biting) forces than to
lateral (shaking) forces (the wider snout of crocodylians better
resist lateral forces).

It seems that if the head was used as in the secretary bird or
seriemas, the proportionally larger size of the head and beak in
phorusrhacids suggest they killed proportionally larger prey when
compared to the Recent birds previously mentioned.