Start by drilling a 10mm hole into the walking sticks handle as showen in the picture, drill about 38mm into the handle and try and keep the hole as straight as you can. Next is to cut a notch out of the walking sticks handle, start by marking 13mm back from the end of the whistle showen on the picture, and cut a straight cut from this mark until you reach the hole you have drilled from before.
Next is to tidy up the notch with a sharp chisel of knife, the more tidy it is the better the sound of the whistle, usually buffalo horn or staghorn are a lot better for making whistle because they are a harder material and make a much better sound. Next cut a 39mm lenght by 10 diameter dowel, shave off almost half the diameter to create a flat surface along the lenght of the dowel. This will be inserted into the walking sticks handle where the hole was drilled.
The final step is to insert the dowel flat side up into the hole until it reaches the notch. Test the whistle and shave off a little more if neccessary. When you are happy with the sound of the whistle glue the dowel in place, once the glue has set cut off the rest of the dowel level with the front of the whistle. This makes all walking sticks stand out, and the great thing is that you always have a whistle near by when you need it.