The cobalt model holds 16 oz food. The perfect ratio of hummingbird food is 1 part white sugar to 4 water. Don't change the 1:4 ratio: too little sugar and they can starve, too much and they can get kidney disease. It is, apparently, perfectly healthy to give them sugar water... they have insane energy needs, and get supplemental nutrition elsewhere. To fill the 2-cup blue model to the brim you would use 1.75 cups water, and a half cup sugar MINUS a tablespoon of sugar taken out. First few times you're doing this, take a pyrex 2 cup measure, fill water to 1 ¾ cup line, dump it in an empty tea kettle to boil. Then take a half cup measure and fill to level with sugar, and take a tablespoon of sugar back out. Dump the sugar in the pyrex, and when water boils pour it over sugar, stir for a minute and it will all dissolve. Allow mixture to cool before pouring in bottle. (the bottle's blue coloring is a plastic coating inside bottle, they're almost all like that, don't melt it). At this point, I have a flock of hummingbirds, and have to fill a bottle every other day, so i've sped this up: measure 1 cup of water in pyrex, put it in kettle to boil. take a half cup measure and eyeball it being 7/8 full of sugar (with experience of having measured as above a couple times), dump it in pyrex. pour hot cup of water in, stir 'till dissolved... make up the rest of the 16 oz volume in pyrex with cold water, and it's cool enough to pour in bottle (you could wait 20 minutes before adding the cool water). The base of the feeder holds almost a half cup, so it's hard to tell when these are empty... the surest sign is when a bird dips it's bill for 1/10 second and doesn't try again at same hole... they may try a few of the holes then leave. To make sure birds always have food, i use two bottles in rotation... when one is almost empty i'll hang a full one next to it (leave the nearly empty bottle in the spot they like better). When I notice birds stop going to the empty one at all, I move the full one to the preferred spot, rinse and let dry the empty bottle and repeat the cycle. Do not over-tighten the base. it's better to have it a little loose on the bottle than to crack the plastic threads. Keeping the feeder's full and fresh is essential to getting a steady flow of birds. The first time we put this up, we left it out a long time... too long... Change out the food at least once a week (they say 3 days) while waiting for them to find it and start coming regularly. I'm in Arizona, and It's rare to go more than 10 minutes without seeing one feeding... And when there's one, that usually draws another trying to do a territorial display. Fun. I can get a crowd of up to 6 birds trying to get at the feeder at a time. FYI, I got my first feeder as a gift, then bought my second feeder here... the first had metal "flowers" the second had plastic. Both worked fine. The one purchased here also had a loose hanging bracket, I used some pliers to bend them just a bit. So construction quality isn't stellar, but the product is so inexpensive that it isn't worth "dinging" a star on an item that's working so well for me and my flock. [apparently the proper collective noun isn't settled... "a charm of hummingbirds" is the common answer, but bouquet, hover, glittering, shimmer, & tune are also offered; but they're so territorial it's hard to think of them collectively!]
