Робота в

механіці.

12.7 All of which still leaves open the question of why some species __________.

12.8 One idea is that favourable winter-summer habitats _________ as a result of the movement of continents, forcing birds to cover just a few extra millimetres each year – but vast distances millions of years later.

12.5 Then again, in terms of the ___________ of intercontinental migration, it’s far from clear that all birds making these journeys today started out travelling north from the tropics during the summer.

12.6 In 2014, Ben Winger at the University of Michigan and his colleagues built a mathematical model to _________  the geographical ranges of the ancestors of hundreds of living species of American songbird.

12.4 Some common swifts flying across the Mediterranean and the Sahara Desert took more than two months to complete the southern journey in autumn, while __________.

12.3 One theory is that it comes down to _______.