What did Frightful need to be able to migrate south?

When a light snow covered the Schoharie River Valley, Frightful’s bird sense urged her one last time to leave or die. On an unusually warm day in early November, she stepped to the open sill of the bell tower. She had caught no food for two days. She must move south.

A semicolon can be placed where a comma can be placed. My trick is to use this rule; replace the semicolon with a comma.

This leads me to:

B) There have been many accidents during airshows, for example, last year the wind toppled a tent and equipment on top of bystanders.

Let me know if you spot any errors or if this works out :)