A platform-style bird feeder will attract many kinds of birds, including cardinals, blue jays, grosbeaks and sparrows. Platform, or tray, feeders offer seed on an open, flat surface usually mounted on a pole. Seed can become wet in a platform feeder, and the best designs use screening as a base, for drainage. Some come with a roof to further protect seed from snow and rain. Regardless of the design, try to put out only as much seed as the birds will use in one or two days, to keep it fresh. Empty the tray and rinse it with a steady stream of water once a week to keep it sanitary, as sometimes bird droppings will collect there.
Trays are effective at bringing in ground feeders like juncos and doves, particularly if they are placed low to the ground, as well as perching birds—and squirrels and chipmunks. To discourage these, try installing a baffle on the pole and adding another platform feeder, sans baffle and closer to trees, for the squirrels themselves. You can also suspend a platform feeder from a tree branch or hanger and place a baffle above it to disrupt squirrels' efforts.
Image: "BCChickadee platform" by Imagination505 - Own work. Licensed under Public domain via Wikimedia Commons.
The Grecian Bird Feeder combines style and function.
For a unique but effective bird feeder try the San Simeon.
Design garden that pleases birds and people with The Living Landscape.