What Does 'Engine' Refer To In The Poem "THE LABURNUM TOP" By TED HUGHES ?

The poem talks about "machine" and "engine". We all know that engine is inside a machine and it is the driving force of a machine. The engine also needs fuel to work. When the poet looks at the tree in the beginning , it is silent and still. When the goldfinch enters its thickness, a machine starts up. The tree is compared to a machine which starts working when the engine is filled with fuel. The following lines makes this clear. "It is the engine of her family. She stokes it full". Engine refers to the chicks int nest. When goldfinch feeds them(fuel), the engine starts working and naturally the machine too. So, tree is the machine. Inside it the baby chicks in the nest, the engine and the food for them is the fuel.

SANTHOSH KUMAR KANA

Engine refers to the life of tree.

It looks like you're both right. 'It' must refer to the tree, but in fact the tree only trembles because it is full of baby birds. So to be exact, the tree is the engine, but only because it contains the nest (family.)

No , the tree is only reffered to as the engine...
Coz the sentence reads, "It is the engine of her family".
If it would have written for the bird then there would have been 'she' used in place of 'it'.....!!!!