The population of birds increases during the month of October because of migration during such conclusions is an example of

Survival.

Explanation

Birds migration is the periodic movement of birds from location to another this is done to secure a good environment condition. Not all birds migrate and their migration is subject to a particular time.

For latitudinal migration, birds moves away from tropic during raining season to a dry place and then returns when the environment is dry.

October is a dry season and migration will favor birds who can do well in the absence of rain hence the increase in population. This is done for Survival.

geographic isolation