Choice of Words: Blue describes the color of the bird, sang is the past tense of the verb 'sing', which means to make musical sounds, and sweetly describes the sound of the bird's singing.
Alternative Expressions
The bird sang a sweet song.
Meaning: This sentence is also describing a bird that is singing, but it's focusing on the song that the bird is singing. It's like saying, The bird was singing a melody that was very nice to listen to.
Choice of Words:Bird is an animal with feathers and wings that can fly. Sang is a verb that means to make musical sounds with your voice. Sweet is an adjective that means pleasant or enjoyable. Song is a noun that refers to a series of musical notes sung or played.