I understand he wasn’t talking about “new species” in the same way that cryptozoologists do, but this thoughtful quote for the day speaks to how we have to “listen” as well as “look.”

The air is full of birds, and as I go down the causeway, I distinguish the seringo note. You have only to come forth each morning to be surely advertised of each newcomer into these broad meadows. Many a larger animal might be concealed, but a cunning ear detects the arrival of each new species of bird. These birds give evidence that they prefer the fields of New England to all other climes, deserting for them the warm and fertile south. Here is their paradise. It is here they express the most happiness by song and action. Though these spring mornings may often be frosty and rude, they are exactly tempered to their constitutions, and call forth the sweetest strains. Henry David Thoreau, 7 A. M. – To Trillium Woods, April 9, 1856.