Answer: Since someone answer got deleted im gonna recover!!
If you guys have the same test on USATESTPERP its C) There is les available food for the birds to eat. If you guys arent on USATESTPERP then here is the other answer
Birds migrate to move from areas of low or decreasing resources to areas of high or increasing resources. The two primary resources being sought are food and nesting locations.-----Thank you also the name is daimonds cuz someone stole the dimonds) name THANK YOU LOVE YOU GUYS! :3