The theme of a poem (or any literary text) refers to the central idea or message provided for the reader. Given that not all readers come to recognize the same message or central idea, themes of a literary piece can differ.
In regards to Mbuyiseni Oswald Mtshali's poem "An Abandoned Bundle," the theme can differ for each reader. The theme will differ based upon how the reader comes to define the message of the poem. Therefore, possible themes for the poem are as follows.
First, one could look at the poem as one which speaks to the desperation of people. Both the speaker and the woman seem to be desperate. The speaker throws a brick at a pack of dogs attacking a bundled infant. The mother, desperate to escape the burden of her child, abandons the child.
Second, the poem could be speaking to the realities of life in South Africa (given the nationality of the poet). The poem details the horrendous nature of the village:
The morning mist
and chimney smoke
of White City Jabavu
flowed thick yellow
as pus oozing
from a gigantic sore.
It smothered our little houses
like fish caught in a net.
The suffering nature of the village is oppressive, like a net over a fish. While the speaker does not show a desire to escape like the mother, the oppressive nature of where they live is evident in both the descriptions of the village and the mother's exit from her life:
had melted into the rays of the rising sun,
her face glittering with innocence
her heart as pure as untrampled dew.
In the end, the theme of the poem cannot be ultimately defined given all readers come to understand the poem in different ways.