Yesterday, I made up a new batch of nectar for my feeder. When I filled one of my feeders, a hummingbird started feeding from it. Within a few seconds, the hummer fluffed up it's feathers while standing on the perch, titled it's head sideways and partially opened it's beak. It was just frozer for about one minute. Other hummers flew up to it but the fluffed up hummer just stood still in it's position with fluffed feathers and cocked head. It was like it was frozen. After about a minute in this frozen state, the hummer finally flew off. The only thing I could think of to cause this reaction was I made the nectar too strong. Has this happened to anyone else?