For those who actually paid attention in science class, please help me understand this. We fill the hummingbird feeders with about 1/4 c. of nectar, and it shows at the neck of the bottle. The next time we look, the bottle looks empty, but the hummers are still feeding from the reservoir. Then, the nectar reappears in the bottle's neck. Is this some kind of barometer phenomenon, or am I going nuts? Please do not answer the second question in the affirmative.