Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Acid rain caused by industrial pollution greatly reduces the number of trees in a forested region that is home to a particular species of bird. How might this decrease in the number of trees most likely affect this bird population?
The population will decrease due to lack of resources.
Population size decreases.