Page "Passenger Pigeon" Paragraph 15

It is hypothesized that their survival was based on the benefits of very large numbers.

There was safety in large flocks which often numbered hundreds of thousands of birds.

When a flock of this huge a size established itself in an area, the number of local animal predators ( such as wolves, foxes, weasels, and hawks ) was so small compared to the total number of birds that little damage would be inflicted on the flock as a whole.

It was common for passenger pigeon flocks to perch on each other's backs, an unusual behavior even for socially inclined birds.