If a bird sings in a forest and a microphone hears it, does it still make data?

Studying birds typically involves in-person observation, but with the rapid advance of high quality audio recorders and microphones, bird researchers are finding they can have "ears" in many places at once these days. How do audio recordings of birds compare to observing them in person? What information do we lose when we don't have visual observations? And what do we stand to gain by using these remote monitoring techniques? This month we're discussing "Bird biodiversity assessments in temperate forest: the value of point count versus acoustic monitoring protocols" (Klingbeil & Willig, 2015).