As a huge fan of backyard bird feeding I found a recent article provided by The Cornell Lab of Ornithology's Living Bird very interesting.  The article focuses on the use of RFID (radio frequency identification) to monitor individual birds feeding habits by placing the RFID tag readers on various feeders in the woods near the Lab.  Tiny 0.1 gram tags were placed on the legs of 129 bird species that frequent  backyard bird feeders ... that is, specifically Black-capped Chickadees, White-breasted Nuthatches, Tufted Titmice and House Finches.  According to the article only 6 hours of feeder upkeep per week provided 8,000 hours of continuous observations with some surprising results.  Read this fascinating article.