very much like the use of the word leaves in the middle, creates a pivot point for the haiku, where the meaning shifts for the reader depending on how they look at it. In fact, the whole haiku has this quality.
the first line could be the bank, on which they rest, or the birds, which come there to rest, the openness created a shared sense of empathy between the two, for without the spot to stop, the birds cannot rest, and without the birds, the bank is not a rest stop.
The second line could be taken as a summer-like day in autumn, autumn leaving for summer to return changed. Or as the autumn leaves changing to show the colors of summer, as summer days slip away.
Then the last line could be the location, the setting for this, or could have a sense of momentum, implying that now they have grazed on the bank, now they will go to the waters edge.
beautiful!!