Fact 1: Harming an animal species causes that animal 's population to decrease.

Fact 2: Habitat loss is the major reason for the decrease in the bird population.

Given the two facts above, answer the question "What has caused harm to the bird population?" with the following options: 
- feral dogs
 - migration
 - habitait loss
 - amoebae
 - hypothyroidism
 - fuel emmisions
 - Pesticides
 - viruses


 

   habitait loss      