I have a hummingbird feeder like this0E9s37F,2HBR(jCHu)2Q~~60_35.JPG) one.
Last night, before we went to sleep, the food level in the feeder was just above the red dish.
This morning, it was at least 1-1.5" higher!
Now, we got a tremendous amount of rain last night, but the feeder is under the eves, and well-sheltered. Could the level have increased due to the hygroscopic nature of the sugar water, and the high humidity?
Should I report this to the Vatican?
one other possible explanation: Water expands with heat. Not sure how much heat would be needed increase the waters volume enough to make to result in a 1" vertical rise, or how much the heat may have changed.
There’s no way you’d get any visible amount of thermal expansion, over any remotely plausible temperature range.
More likely explanation: You have neighbors who also like watching the hummingbirds, and one of them decided to refill it for you.
At night, everything got cooler. The liquid probably did not change volume much but the plastic container just might have in a place that would make one part look much different. YMMV
Unless they are very tall, I don’t think this is a plausible explanation, since it’s hanging outside a second-storey window.
It’s also exceedingly unlikely that anyone in our house refilled it, since it’s my job, and I know my wide didn’t do it.
It’s a stumper…
Any chance the rain was able to enter the feeder? Blowing rain, etc.? But no matter what, by all means contact the Vatican. And where is Colibri when you need him?
I really don’t think so.
Even if it did, I don’t see how it would force the liquid back up the container - the feeding holes set an absolute limit on the level of the food in the tray.
One thing might be barometric pressure - yesterday evening was right before this huge storm, which means the pressure was low.
Hmm… maybe that’s it.
Looks like the pressure was 29.72 inHg at 7pm on Sunday, and 29.93 at 11 AM today.
So, .21 inHg = 2.85 in H20
Must be it!
Maybe the hummingbirds are screwing with you, putting some back. 
Depending on the layout of the feeder, barometric pressure might account for it. Do you have a picture of the feeder?
Yes0E9s37F,2HBR(jCHu)2Q~~60_35.JPG).
Check for any hummingbirds that are flying backwards. They might have gotten reversed in time, and are actually regurgitating liquid into the feeder when they visit it.
I have a sheltered porch and packages will get wet when it rains because of the blowing wind. Chances are about 99.99% that water is penetrating the feeder in a blowing rainstorm or possibly you were at an odd angle when you observed the initial level and this is all a huge mistake based on visual angle or similar parallax errors in your initial observation. If the choice is magic or errors in observation the smart money is usually on human error.
Is the feeder air tight? Could it be that overnight cooling caused a drop in pressure inside the feeder, drawing the liquid up?
I don’t think it’s a coincidence that the wettest day ever recorded in Phoenix was the same day that your hummingbird feeder mysteriously filled with water.
Or using the feeder as a toilet.
The feeder has to be airtight. If it weren’t all the liquid would freely flow out and down to the ground.
Change in temperature explains the change in liquid level. While the liquid won’t change much volume, the AIR will change quite a bit. Judging by the picture, the upper part of the chamber is bigger than the bottom neck. If the liquid level was in the neck part to begin with, then a volume change in the air (big upper part!) would easily translate to an inch or more liquid level change (small lower part).