ST. PAUL, Minn. — Along with spring, migratory birds are back. More than a century ago, their seasonal arrival was the object of intense interest by one of the state's most important ornithologists, Thomas Sadler Roberts.

Roberts wrote "The Birds of Minnesota," regarded by many as a definitive account of Minnesota's winged creatures. His biographer, Sue Leaf, spoke about him recently at the wildlife sanctuary named in his honor.

Her new book is called, "A Love Affair with Birds." Click on the audio link above to hear her speak with Minnesota Sounds and Voices producer Dan Olson.

Listen here.