You are presented with the question "What undergoes a movement that changes population size?" and the following answer choices: 
- Wasps
 - camels
 - sheep
 - insects
 - animals
 - sharks
 - birds
 - ducks

Now knowing that migration is a type of movement that changes population size and bird Migration and Isotopes Tracking animal migration is a difficult task, choose the best answer.


 

       birds  