GrrlScientist wrote an excellent piece on Medium, "Passenger pigeon extinction: it’s complicated," about new research behind what led to the extinction of the Passenger Pigeon. It's an interesting look at the how population fluctuations and human-based causes led to the demise of a once abundant bird. There are certainly lessons to be learned and correlations to our own campaign to save the Tricolored Blackbird from a similar fate.
HOTSPOT: Flyover of California's Birds and Biodiversity
California is a global biodiversity hotspots, with one of the greatest concentrations of living species on Earth.