Hello...my wife and I are not birders but are blessed with a rooftop garden none stories up in downtown Brooklyn. We are visited by many birds throughout the year. My wife types them with her Audubon book. We always have nesting mourning doves and dissuade Mocking birds likewise. It is a big garden and there are always some birds about. We do not feed them as we are not here all the time. We have an interesting question though: All plants (conifers, maples, shrubs) are in containers. Every year we must weed out oak tree seedlings that are still attached to the acorns. Our bird population includes Mocking Birds, Mourning Doves, Robbins, local finches and sparrows and the occasional Blue Jay. We have not witnessed a bird carrying or burying an acorn. Who is the culprit?