Question

Why is the image of the engine evoked by the poet?

Answer 1

The image of the engine is evoked by the poet because it serves as a source of energy for the purpose of runnig machine.

Similarly the bird serves as a source of energy for its family. The way a machine cannot work without an engine, similarly the family won't be able to survive without the bird. 

Answer 2

The bird is described as the engine because this bird helps the whole family members to survive..She feeds them...