I made this bird feeder because I didn't want to drill any holes into the building where I live, so this just plops in place in the window sill and is good to go. It will work in any modern window.
Step 1: Gather needed items
1-Frame--I used an old screen print frame, but I bet any old frame would work.
2-Mesh or Screen--for bottom of tray, something permeable, but that seed won't fall through
3-1/2" or 3/4" piece of wood the same length of the longest side of the frame you chose
4-L-shaped fastener with screws
5-Long nails or Screws, a hammer, and a drill if you have one
Screw the L-shaped fastener onto the wood plank as pictured, so that it will latch over the lip of the window sill. Screw another one to the other side of the wood plank.
Step 2: Fasten mesh to tray bottom
Nail into place the mesh you chose for the bottom of the tray. In my case, I used an old bamboo-like window blind. I cut out the shape I needed and nailed it all into place on all four sides so that it wouldn't buckle anywhere.
Step 3: Attach tray to wood plank/fastener
Use long nails or long screws and attach the frame to the wood plank.
Step 4: Install to window
Put the bird feeder tray in place in the window--and keep in mind that if you don't attach something to the bottom to hold it in place, it will fall if you let go of it before you pull the window closed.
Add your seed. And hold in place and close the window.
Step 5: If you build it, they will come
About two minutes after I added some seed, this little titmouse was the first customer.
Step 6: Invite local birds
This little warbler was the next to visit.
You can see the fasteners well in this photo.
Step 7: Finally
One of my cats caught wind of what was going on and the rest was history.