There are various possible meanings to this song. One is it's about an actual bird who wants to be free and fly away. The other is metaphorical-- it could refer to the a person who has been captive (whether enslaved, imprisoned, in a bad relationship) and has been waiting for so long for the moment of freedom to arrive. Paul McCartney himself told ABC News in a 2001 interview that "I wrote it in the '60s, when the civil rights movement was at its height. I liked to think of a blackbird as being a kind of symbol for a black woman."

another comment from a contributor:

Since the Beatles are from England, they call women birds. Blackbird was written when Paul McCartney was just sitting while he had free time on a tour. Then he heard a women screaming and a lot of police cars pulled up. The police had her handcuffed and were beating her. There was a giant crowd. Paul thought the black women committed a huge crime. Turns out all she did was sit in the whites section. Paul was shocked, as there was no segregation in England. He decided to write a song. Notice how all the adjectives are negative: dead,dark, sunken, broken. They describe the unfairness. The verbs show the actions of the black people: fly, singing, free, arise, waiting and see. After all those tragedies the African Americans didn't use violence. It was the lady's time to be free and arise from the dark black night. There is also the sound of a foot beating in the background. The footsteps represent the marching of all the African Americans, longing for freedom.

and another comment from another contributor:

McCartney in 2002:

"I was in Scotland playing on my guitar, and I remembered this whole idea of 'you were only waiting for this moment to arise' was about, you know, the black people's struggle in the southern states, and I was using the symbolism of a blackbird. It's not really about a blackbird whose wings are broken, you know, it's a bit more symbolic."

(Radio interview with KCRW's Chris Douridas, May 25, 2002)

McCartney in Rolling Stone Magazine:

"I had in mind a black woman, rather than a bird. Those were the days of the civil rights movement, which all of us cared passionately about, so this was really a song from me to a black woman, experiencing these problems in the States: 'Let me encourage you to keep trying, to keep your faith, there is hope.' As is often the case with my things, a veiling took place, so, rather than say, 'Black woman living in Little Rock,' and be very specific, she became a bird, (she) became symbolic."

this sounds like a little nightmare.

More information:

This dream might have multiple interpretations. The challenge lies in determining what the blackbird represents to the dreamer.

In the U.S.A., during the racially charged 1960s, a blackbird on fire could have symbolized a lynching. Children's nursery rhymes are full of blackbird stories, like those baked in the king's pie. There is John Lennon's Blackbird and Blackbird by Alter Bridge. One of these is significant, but only the dreamer can recognize the connection to the dream.

The second element in this dream is fire which is destructive: fever or passion. The blackbird could represent a part of the dreamer's body (the song/voice?) that is burning with fevered infection, or it could represent a dark passion. Again, the fire in this dream has a significance that is specific to the dreamer.

While this exploration may seem more confusing than helpful, once one understands how symbols function, the dreamer might recognize the meaning of the dream immediately. For example, someone who lives on Blackbird Lane during this summer's blazing heat wave would know instantly what the dream means to them.

The attached link contains further information on dreams and their symbols.

Foreshadowing in the book is "I am going over to see Hannah Tupper," she announced, trying to sound matter-of-fact.

"The witch? Have you lost your senses, Kit?" Judith was scandalized."(Page 95 in my book) That is foreshadowing because it shows that Kit befriends Hannah but many People don't like Hannah, so when the people figure out Kit befriends Hannah, they will try to give consequences.