Coo is placed as a baby on the street outside a tall building and below a rooftop dove cote. A much-smarter-than-the-rest-of-the-flock pigeon takes pity on her and directs the flock to grab her swaddling and lift her up. They do, and Coo doesn't set foot on the ground until she's 12 and needs to get help for her benefactor, after his wing is damaged in a hawk attack.
Now, at this point, lest you think pigeons don't live that long, let me reassure you, they do and then some! My son went through a Don't Let the Pigeon Drive the Bus! phase and he found a fancy pigeon for sale at the state fair and begged us to buy it for him. We researched pigeons, and quickly turned him down. They can live up to 35-40 years! There was no way I was scooping pigeon poo well after my son had graduated from college!
In any case, Coo finds an ally in the old woman who feeds the birds. The woman takes the pigeon to "heal" him and gives Coo a warm red scarf and hat. Then a bitter freeze hits, and the woman comes back with the police to make sure Coo's okay. She hides from them, only coming out when the woman comes alone. Coo lets the woman take her to her apartment, where she's caring for her pigeon friend. He's okay, but he'll never fly again.
The old woman, meanwhile, has to explain to nosy neighbors where Coo came from and how in the world she shows up in her flat. Coo has to decide if she's going to stay where its warm and she's loved, or head back to the flock, where perhaps she's not as needed as she had thought she was.
I won't spoil how it ends. The book is ultimately about finding one's family, even if it isn't a traditional one. Enjoy!