This instructable will cover all the basics involved in building an electronic canary. This is a excellent weekend project. This circuit recreates accurately the sound produced by a canary.
All components for this project should cost under $10
Basic soldering and electronic skills required

For a preview for the sound it makes. The file is below the picture.

Electronic Canary.wma
Download

Step 1: Preparation

Equipment Required

Soldering Iron
Pliers
Work Station

Parts Required

Resistors
1 x 47k Ohm
1 x 4.7k Ohm

Transistors
1 x BC109 or BC337

Transformers
1 x 1K:8Ohm Audio Transformer

Capacitors
1 x 22nF Ceramic
1 x 10nF Ceramic
2 x 100uF Electrolytic

Other
1 x 9v Battery and Clip
1 x Plastic Board
1.5m of Copper Foil Tape
1 x C2222 8Ohm Speaker
1 x Momentary Push Switch

Step 2: Assembly

First plan out your copper foil tape on your plastic board. Start to stick the pieces of your tape onto the plastic board and then start to solder on your parts one by one. Be careful when soldering the transistor as it is heat sensitive. Anything more than 5 seconds with the soldering iron on the transistor will burn it out. After soldering on all your components, make sure your solder joints are nice and clean. if they are dirty apply some heat using your soldering iron. Also make sure you have the correct audio transformer otherwise the sound does not work properly.

Step 3: Testing and Troubleshooting

Now put a fresh 9v battery in and test the circuit. Push the switch and a canary chirp should be audible. If this is not the case check these following things

1. Check the Transistor legs
2. Make sure the transistor has not burned out
3. Make sure the battery in the right way
4. Make sure the legs of the transformer are wired properly
5. Check all your solder joints to make sure they are clean.

If all of these are followed your circuit should be operational