Piranhakeet

Piranhakeets are Croodaceous birds that are unquestionably the most deadly predator in their environment. They are a cross between a Parakeet and a Piranha.

Behavior
Spending the day safely underground, they emerge at nightfall to swarm across the sky in a beautiful cloud of red and magenta. Upon sighting any movement, they condense into an ominous tornado-like hunting formation to swarm their prey and strip off every fragment of organic material in seconds, leaving nothing but a perfectly untouched skeleton. Their only exploitable weakness is their fear of light and/or heat. This is the reason that they remain underground during the day and are tremendously afraid of fire.

In the Movie
A flock of piranhakeets is seen when the Croods first arrive in the valley, emerging at nightfall and scaring off the macawnivore, a herd of swamp tree elephants, and a colony of ground whales. One ground whale is unable to make it underground in time and is rapidly reduced to a bone pile. The swarm then attacks the Croods, but are effectively warded off by Guy and a flaming torch. They later are used by Grugg, Chunky, Douglas, a liyote, and two trip gerbils to escape the valley right before the End destroys it. They are lured by Grugg into a tar-lathered ground whale skeleton, sticking to it like flypaper. Grugg then lifts a torch up to them, spooking them into taking off and lifting the skeleton and its passengers over the chasm into Tomorrow.

Trivia
The Piranhakeets were inspired from a similar looking (and named) creature from an episode of "The Wuzzles", a Disney animated TV show with, ironically enough, hybrid animals. They in turn, were inspired by a similar creature that appeared in a Season 2 episode of The Flintstones.