I looked in my heart while the wild swans went over.
And what did I see I had not seen before?
Only a question less or a question more;
Nothing to match the flight of wild birds flying.
The opening line begins without preamble; the poet is reaching deep within herself (‘looked in my heart’) and relating her soul-searching to the image of the swans. The line is  end-stopped  for emphasis. 

Wild Swans