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 housing of the mic was modified in 2024 and again in 2025. The current model shipping is the v2025. It has the same functionality as the earlier models but is housed in a smaller 1-gal bucket and has the cable hard wired into the mic (no connection) -- the purchaser specifies the length of cable needed.
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, it is ready to be connected to a listening or 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.