I love watching our little ruby-throated hummingbirds from my office window. I have three feeders, strategically positioned such that there is no available vantage point from which the birds can see more than one at once. They aggressively monitor and defend their food sources, and if one bird can see all the feeders, it will attempt to chase other hummingbirds away from all of them (despite the fact that each feeder has about 50X more sugar-water than a single bird could drink before it goes bad).
These little guys and gals will be departing soon, headed south for their winter homes. This tiny little bird, which weighs about as much as a penny, two pennies at most, will fly all the way to Central America, including a 900-mile non-stop flight across the Gulf of Mexico. Incredible.