Read the passage and answer the questions that follow.
Bella was fed up and bored of being cooped up inside. So, as soon as the weather seemed to be getting better, she took the opportunity to stretch her legs and get some fresh air. And the air was exactly that. Other people may call it icy with an unpleasantly strong wind, but for the girl, it was exhilarating and refreshing. She had wrapped up warm, in a large overcoat and hat, gloves and scarf. Her fingers had a tendency of getting much colder than the rest of her body, so she always wore gloves when the temperature was under five degrees. On this day, she wore her favourite pair that were very insulating and made of natural fibres and kept her hands warm.
Bella opened the front door and made bold strides down the path to get her blood moving properly. After a few minutes of walking like this and using lots of energy, she was just as warm as she would have been at the height of summer. She took her hat off and her hair blew in the wind. Her ears were a little chilly, but they helped to cool the rest of her as she walked on briskly. She was generally very healthy and put this down to the fact that she loved to walk, whatever the weather. She felt that less healthy people would stay at home on a day like this one, but they wouldn't be as happy as she was.
She thought that the fresh air definitely lifted her entire mood, and she went from feeling sombre to excitable and full of energy.
The trees had lost most of their leaves and their skeletal figures were clear against the grey sky. Bella looked up at them and could see birds perching with difficulty, struggling to keep themselves in place while the wind tried to blow them away. Some birds occasionally gave up and let the wind carry them with great speed, to wherever it seemed to want them to go. She thought this was a clever but scary thing for them to do. Bella wondered why the wind seemed to be in such a hurry today. She was walking against it, but it was still trying hard to push her towards the place that the birds had been taken. She resisted and strode on.
Bella thought the birds were _______.