Argentavis

The largest condor known to man, it has a wingspan of over 7 meters and weighs between 70 or 100 kg. It is said the native american legend of the Thunderbird came from these winged monsters.

Role in the story
A flock of Argentavis discovered the group's settlement, 3-6, and later attacked, seeing the humans as easy-pickings. They also infested the settlement with poisonous ticks from their own bodies after they were chased off.