Given the poem's title and opening lines, readers can quickly gather that the speaker is at a zoo. At this zoo, the speaker comes across "apes" who "yawn and adore their fleas in the sun." In other words, these magnificent creatures—and humankind's closest animal relative—seem totally bored as they leisurely groom each other in the sunshine.
They're so bored, in fact, that they "adore," or as in worship/pay close attention to, their own fleas, which apparently offer their main form of entertainment in captivity. And right away, the poem's sounds evoke this dull atmosphere: notice how the long, drawn-out sounds of "yawn" and "adore," for example, and the clear end-stop that closes the line with a firm pause.
The speaker moves on to the parrots next, which, while more active, aren't any more impressive than those apathetic apes. The speaker uses two similes to hammer home the birds' unhappiness:
- They either "shriek" like they're on "fire," suggesting that their cries are grating and reflect the birds' sheer terror (perhaps at the fact of being caged);
- Or they "strut" like "cheap tarts" (meaning promiscuous women/sex workers) in order to get nuts from the crowd.
Either way, they're not doing what birds are made to do: fly. Instead, they've been reduced to "cheap" entertainment. The mention of a "stroller" makes the scene all the more dismal and degrading in the speaker's mind: these wild animals are mere amusements for people wandering idly past. Notice, too, how the poem's flashy, sneering consonance evokes the speaker's distaste for that "strutting" about, with the mixture of crisp /t/ and hissing /s/ sounds in "Parrots," "strut," "tarts to attract," "stroller," and "nut."
Also pay attention to the anaphora and parallelism of lines 1 and 2, whose opening phrases follow the same grammatical structure:
The apes yawn and adore their fleas in the sun.
The parrots shriek as if they were on fire, or strut
This anaphora suggests the monotony of life at the zoo.