Step 1: Things You'll Need for Building
These things are
>Bits of wood
>Means of Screwing and/or Nailing
Step 2: The Plan
What the diagram attach shows is the basic principle of the thing. You have two legs for support and a top for the owl treats as well as sturdy landing pad for your new fowl friend.
The length of the boards are entirely up to you.
Step 3: The Treats
Mice fit the bill quite nicely and can be obtained many ways.
Step 4: The Wait
(Please note this owl is from the internet[owl-pictures.net])