题目内容：

阅读下面短文,在空白处填入1个适当的单词或括号内单词的正确形式。

In late April 2017, a violent storm swept through the southern United States, 1.(destroy) more than $ 1 billion in property and killing 35 people. But it was 2.wonder that a group of birds sensed the oncoming disaster and left long before the first clouds arrived. A year earlier, a science team had tagged golden-winged warblers (莺) with leg trackers 3.( study) their annual migrations to South America. Two days before the storms 4.(strike), five golden-winged warblers flied away, traveling south to the Florida coast.

It's the first time that the birds which normally migrate with the seasons 5.(observe) to fly away when a big storm hits. The researchers suspect this behavior occurs only when the threat of 6.(injure) outweighs the energy costs of a long trip. But nobody knows 7.the birds guessed the storm's harm and left so soon. 8.( puzzle) by it, the scientists initially reasoned that changes in weather—atmospheric pressure, temperature or wind speed—signaled the upcoming disaster. Yet when they checked weather records, none of these factors waved 9.(significant) before the storm. Instead, the team thinks that the approaching storms created a disorder of infra sounds, low-frequency sound waves, that birds can hear, 10.humans can't.