A couple of weeks ago, as I wandered through towering ash forests in the foothills of the Dandenong Ranges, I found myself in the middle of an eastern whipbird conversation. Just to the left of the track, a male sang his drawn-out whip-crack, which was swiftly followed by the female's "tyoo-tyoo" response from the undergrowth on my right. This distinctive duet, a staple of the Australian bush down the east coast, was just one of a handful of bird calls I heard during that walk, and probably dozens more that slipped under my radar. It struck me that it's rare…