An "aubade" is a poem, or piece of music, written about dawn or morning. Those of you who are not early risers might need to snag a cup of coffee before you can get on the same level of psyched as the speaker in this poem.
Wilbur probably titles this poem "A Late Aubade" because, well, it's a poem about the late morning. An aubade is generally positive, and often has to do with love. As we find out, this poem has a lot to do with both morning and love. Because the title tends to cast a shadow over the poem, or set the tone of a poem, before we even begin reading there is a romantic and cheery presentiment about what's to follow.
Wilbur doesn't disappoint. Before long we're thrust into a poem that's radiant with morning love. Maybe Wilbur thinks the best part of waking up isn't Folgers in your cup, so much as having the one you love by your side.