And the eyes of those two Indian poniesDarken with kindness. (3-4)
Don't these lines just make you feel all warm and fuzzy? Love has a way of doing that. And kindness is one expression of love.
They ripple tensely, they can hardly contain their happinessThat we have come. (9-10)
When people love each other, they are happy to spend time with each other; when separated, they can't wait to see each other again. The ponies' enthusiasm about the arrival of their human guests suggests a similar level of anticipation and affection.
They bow shyly as wet swans. They love each other. (11)
This line leaves no doubt that the ponies love each other; the image of bowing swans even suggests romantic love. By introducing the word "love" at this point, right in the middle of the poem, the poet brings the theme of love front and center.