Window bird feeders are no more than an extension of your present window sill or opening. According to these plans all that is necessary is to attach a horizontal member the width of your window and just underneath your sill or opening. The distance just under your window sill should be the very same as the thickness of the tray itself. This will allow the tray piece to set on top of the horizontal piece and be level with the sill or opening. Cut your tray to extend outward ten or twelve inches and run the width of the window. Place, then affix the L-brackets underneath the tray with the longer leg of the L-bracket underneath the tray. Affix the shorter leg of the L-shape to the horizontal board you attached to the outside of the residence just beneath the window . The two L-brackets should be spaced to allow for the greatest support. If your feeder tray is wider than an average window and is very long, you need to have more brackets to support the weight evenly.
For flexibility, you may want to make a three sided cover the very same size as the depth of the tray to shelter the birds and the food. Some birds favor the protection, but other species don’t seem to mind the exposure. The shelter is convenient in the winter though, when snow is likely to cover the birds’ feed. On top of that, the shelter keeps the water out in the spring and summer months which helps keep the food fresh. Remember not to attach your little cover to the tray so you can readily remove it when the tray needs cleaning.
As to the top rated wood to use, redwood cedar is best for durability, but most any wood will do except pressure treated wood. Pressure treated wood has chemicals that can harm the birds. You shouldn’t paint your tray either as the birds may pick up paint flecks as they eat which can also poison them.
What variety bird food you set out is entirely up to you as different types of foods will entice different species of birds. Foods typically present in your house will suffice or you can obtain commercially processed bird feed. Birds’ eating habits range from suet (hard beef fat, especially needed in the winter) to bread crumbs, raisins, fruits, bacon bits, and peanut butter. Surely, all of these things can be found right in your own kitchen and won’t cost anything more.
In closing, remember that some birds will be afraid to come to your window area to eat because they feel exposed out in the open and next to the window itself. You can change that easily enough by choosing a window near foliage or trees. If that is not possible, place some vegetation both inside the window and outside on the feed tray to make the birds feel safe.