Great podcast for the perpetually curious: Pigeon milk, among other things

Point of Curiosity: What is pigeon milk?

A friend of mine recommended this podcast about a book. I'm not very aural, but this completely captivated me. Do you KNOW what pigeon milk is? Find out.

This is a podcast, and a book, for those of us intrepid urban hikers who wander out into cities and still find and admire the nature all around us.

The podcast (99% Invisible):
http://pca.st/pCFE

The book:

Unseen City: The Majesty of Pigeons, the Discreet Charm of Snails & Other Wonders of the Urban Wilderness by Nathanael Johnson