/ɪnˈdjʊə $ ɪnˈdʊr/ (v.) to live under difficult conditions … winter season in nearby valleys, enduring some of the coldest conditions on Earth.

/əbˈzɜːvə $ -ɜːrvər/ (n.) a person who watches something If birds become aware of the presence of an _______ , they quickly fly away.

/fiːt/ (n.) a difficult act or achievement Modern-day researchers have attempted to understand this _______ .

/ˈfæsəneɪt/ (v.) to interest greatly The study of the lives of birds _______ s many people.

/ˈfjuːəl/ (v.) to provide energy About 55 percent of bird body weight is made up of the fat necessary to _______ this amazing journey.