Old Bird 21c
The Old Bird 21c is a directional microphone & preamp specifically designed for monitoring avian flight calls. The microphone has superb sensitivity and outstanding reach into the sky for flight calls of most migratory birds. It is especially well suited for residential rooftops that have a clear view to the sky (no overhanging trees). The mic was first released in 2010 and its electronic circuitry was upgraded in mid-2020.
The system includes microphone, preamp, AC power connector, and audio cables. It runs on 120V AC (wall socket) or a 12V DC source (not included) for remote operation. Once powered, one can connect speakers to listen directly to the sky and/or record sky sound by running the audio signal into a computer or other audio recording device.
The 21c's mechanism for waterproofing and protection involves a thin plastic wrap and nylon cover that should be changed annually (more often in high UV regions like AZ, TX or Mexico). In addition, the core microphone element loses sensitivity over time and should be replaced every five years or so to maintain optimum sensitivity.