Birdmigration(遷徙)Themanreasonformigrationormovementisfo...
問題詳情：Birdmigration(遷徙)Themanreasonformigrationormovementisfood;forexample,somebirdsmaychoosenottomigrateiftheyarefedthroughthecoldmonthsChangesinthedaylengtharesignalsformigrationandrelatetotheph...