1 . 碧空如洗的秋天是用望远镜观察这类老鹰习性的最好时节。(when)(汉译英)

2 . By the closing decades of the 19th century, the hardwood forests ________ passenger pigeons nested had been damaged by Americans’ need for wood, which scattered(驱散)the flocks and forced the birds to go farther north, ________ cold temperatures and spring storms contributed to their decline. （用适当的词填空）