How does joining a flock most likely increase an individual bird's chance of survival

Here are the reason why joining flocks will increase their chance of survival:

- Protection from predator
Their predator (such as falcons) can only get one bird at a time. Joining a flock will reduce their chance of being caught because they are moving in large unstoppable mass.

- Conserving heat
Being around the flock will help them maintain their body temperature to survive a harsh winter.