YES! You are correct.
Though unfrozen water and a location near a wild area are not absolutely necessary to attract birds (as many urban feeders will attest), to be "most successful" (defined as "getting the most of different kinds of birds"), being in or near a wild area and providing a source of unfrozen water will definitely be helpful. For those who can't have those, however, providing some nearby cover (5-6 feet from feeders) and different kinds of feed in different locations - - on the ground, platforms, hanging, etc. - - will provide a good deal of success.
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