Real hummingbirds are the most energy intensive birds. They have a very low margin for error, a few hours without feeding at best.<p><a href="http://www.blurtit.com/q890088.html" rel="nofollow">http://www.blurtit.com/q890088.html</a><p>"A 4-gram hummingbird has a basic metabolic rate of 1,400 calories per gram. In repose, a hummingbird's metabolism rate is 25 times that of a domestic fowl. If a person had such a high metabolic rate, he would have to eat twice his body weight daily, his temperature would be 750 degrees F, and he would consume 155,000 calories per day."<p>It's probably marginally better than helicopters.