The poem reads like a few moments of attention caught mid-flow. It starts with a man in the street, and then a thought about how many people seem disturbed in married life. The sentence breaks off and drifts, as if the speaker is half-listening to the world and half-brooding. Then the focus jumps: a bird, maybe a gull, though the speaker isn't sure, and some boys imitating it.
Nothing is explained, and that is the point. The poem doesn't tell us why the speaker is thinking about troubled marriages, or whether the man in the street has anything to do with it. The jumps feel like real perception, where a heavy thought gets interrupted by something small and ordinary.
The mood is quiet, a little uneasy, but lightened by the boys' play. The speaker seems an observer rather than a participant, noticing, wondering, and not settling on any one answer. The question about the gull adds a note of gentle uncertainty.