What size hummingbird feeder should you get?

The arithmetic, shown

Here is the whole thing, using published figures and one assumption we will state openly.

The fixed input: nectar must be changed every three to five days in moderate weather, and daily in very hot weather. That is Cornell Lab guidance, and it is not negotiable, because what is being prevented is fermentation and mold.

The variable input: how much your yard actually drinks. This is the number nobody can tell you in advance, and anyone quoting you a precise figure for a yard they have never seen is guessing. It depends on how many hummingbirds visit, whether they are resident or passing through, what is flowering nearby, and the time of year.

The rule that falls out: the right capacity is whatever your birds finish in roughly the same time the nectar would spoil anyway. Anything above that is waste, because you are pouring it out on the same schedule regardless.

So the practical method is to start small. Buy 8 to 12 oz. Fill it. If it is empty in a day, buy a second one — or go up a size. If half of it is going down the drain every third day, fill it half full next time. The feeder tells you the answer within a week, and no article can.

Why the instinct to buy big is wrong

The mental model people bring is a dog’s water bowl or a seed feeder: bigger means longer between refills. Seed genuinely works that way — dry seed sits happily for weeks.

Sugar water does not. It is a warm, dilute sugar solution sitting outdoors, which is close to an ideal medium for yeast and mold. Its clock starts when you hang it and it does not care how much of it there is. Buying a bigger feeder buys you nothing except a bigger thing to wash.

Two feeders beat one big one

If your problem is genuinely “the feeder keeps running out,” the better fix is usually a second feeder rather than a larger one, and for a reason that has nothing to do with volume.

Hummingbirds are territorial. A dominant bird picks a perch with a view of the feeder and drives off everything that approaches, all season. It cannot do that to a feeder it cannot see. Two 8 oz feeders on opposite sides of the house will show you more birds than one 32 oz feeder ever will — and each one still gets washed as a small, quick job. More on this in where to hang a hummingbird feeder.

Fill level: you do not have to fill it

A slightly obvious point that people miss: capacity is a maximum, not an instruction. A 16 oz feeder filled to 6 oz works exactly as well as an 8 oz feeder, and you can adjust week by week as the season builds and fades.

There is a caveat for bottle feeders. A partly-full inverted bottle has more trapped air above the nectar, and more air means more expansion in the sun and more dripping. If you have a bottle feeder and want to run it half full, expect a bit more drip — or switch to a saucer, where fill level does not affect anything. See why feeders leak.

Seasonal sizing

Demand is not flat. Early spring, when the first arrivals show up, is quiet — a small feeder, filled shallow, is right. Mid-summer with fledglings around is the peak. Late summer and fall migration can be surprisingly busy again as birds fuel up to move.

The easiest way to handle that is not to buy for the peak. Own a 12 oz feeder and adjust the fill level, or own two small ones and hang the second only when you need it. Timing is on when to put feeders out and when to take them down.