Birdmigration(迁徙)Themanreasonformigrationormovementisfo...
问题详情：Birdmigration(迁徙)Themanreasonformigrationormovementisfood;forexample,somebirdsmaychoosenottomigrateiftheyarefedthroughthecoldmonthsChangesinthedaylengtharesignalsformigrationandrelatetotheph...