观鸟者和其他人如何帮助鸟类迁徙

migration - n. the act of moving from one area to another at different times of the year

alert - adj. able to think clearly and to notice things

decline - v. to become lower in amount or less in number

range - n. the area in which an animal or plant naturally lives

habitat - n. the place or type of place where a plant or animal naturally or normally lives or grows

species - n. a group of animals or plants that are similar and can produce young animals or plants

reflective - adj. causing light, sound, or heat to move away

visible - adj. able to be seen

global - adj. involving the entire world

drought - n. a long period of time during which there is very little or no rain

aerial - adj. performed in the air

insectivore - n. an animal that eats insects