I found this circuit at 5 or 6 different websites, all identical except some were in color, others not. The schematic and part values were all the same. I didn’t have a 1k CT to 8 ohm transformer (Radio Shack 273-1380) so instead I used a transformer with four 600 ohm windings and I tied two of the 600 ohm windings together to make the primary. I tied the remaining two windings together in parallel to drive a small magnetic beeper. The beeper wasn’t a proper load like a speaker so I put a 1k resistor in parallel with the beeper. I used a PN2222A in place of the BC109. I put two 22k resistors in series for the 47k.The schematic calls for a 9V battery but I used a 4V solar cell, which is not as loud but it’s okay. The sound depends on the transformer, the speaker, the power supply voltage and of course on the values of the capacitors and resistors. You will have to choose values to suit your situation. The chirp sounds like a crying squirrel — see video below.
A 3 second video with sound.
2020-07-09 Chirping Bird Circuit
