The Fledgling, by Jane Langton

Georgie was just about the most unusual girl. She thought she could fly and she was probably the skinniest person in the world. But Georgie knew she could fly. She had done it it before. She had floated down the stairs in two graceful steps. Eleanor and Eddy (Georgie's cousins) thought that she would kill herself if she tried to fly down the stairs again. Georgie always ended up crashing. "She really thinks she can fly," Aunt Alex said. "Maybe she can," Uncle Fred said. "She's such a skinny little thing."

Georgie sat on the porch, reading. When some geese came flying over, Georgie looked up. "The swans!" Georgie said. The swans were not white, like the ones in her book. They were white, and grey, and black. The biggest swan was coming down, but Uncle Fred came outside and scared him away. Georgie was sure the big swan wanted to teach her to fly. When she found out that they were geese not swans, she called him the goose prince.

One day Georgie went on a walk, to see if she could find the goose prince. She was just about to cross the street when a man (Ralph Preek) drove up. Ralph Preek saw the goose prince come flying to Georgie, and he thought the goose was attacking her. He scared the goose prince away and drove Georgie home. Then the goose prince only came at night, and he taught Georgie how to fly. But hunting season is coming, and Ralph Preek will stop at nothing to kill Georgie's beloved goose prince.