Have you ever heard a red-headed woodpecker chirping?
Here is an electronic bird capable of reproducing the sounds of the red-headed woodpecker. If you have them around your house they might fly near by to try to see this electronic relative!
The key provides more convenient control when carrying the kit around outside as you try to attract birds with your bird calls. You can also try the 9V supply.
The output is louder and resembles even more the scolding chirps of the redheaded woodpecker. The chirps with the 3V supply circuit resemble more the English sparrow.
When experimenting with this circuit you can change almost anything without causing damage. However, do not decrease the 47K resistor to below about 10K or the transistor can be damaged.
Some combination of resistance and capacitance in place of the 1K and 100µF results in some interesting sounds from crickets to bears! Don't forget to record your results for later use, like a good scientist does.