Making a Clipping Mask is pretty easy with Photoshop CS4.
First make a selection of the area you would like to mask. Using your selection tool of choice for this post I will be using the Quick Selection tool.
Using this tool I quickly select the image of the bird.
I then open the Paths tab and click on the corner menu and select “Make Working Path”
I then choose 2.0 tolerance ( you may choose differently) and click ok
The on the paths menu you choose
Save Path – Name the path whatever or use the default – Click ok
Then on the menu you choose
Clipping path – Make sure you are clipping the correct path in the dialogue and click ok
You now have a clipping path!