How can these two simple sentences be combined to create a complex sentence? The birds flew south for the winter. It was time to get out the sweaters.
1 The birds, flying south for the winter, told us it was time to get out the sweaters.
2 When the birds flew south for the winter, it was time to get out the sweaters.
3 The birds flew south for the winter; it was time to get out the sweaters.
4 The birds flew south for the winter, and it was time to get out the sweaters.