Sugar solution for hummingbirds
Typically it is recommended to add 4 parts of boiling water to one part granulated sugar. Let the mixture cool down before adding it to feeders to avoid damaging the feeder and burning the hummingbirds. Hummingbirds will drink higher concentrations of sugar but they will visit the feeder less often and these concentrations may not be good for their health. The concentrations I have recommended replicate the typical nectar concentrations found in flowers that they feed from.
It is important to change the solution every four days in warm weather because the sugar ferments and also because it may become mouldy. Never feed honey to hummingbirds because it ferments rapidly, does not contain the same type of sugar and because it may be the source of a fatal tongue fungus.
Clean feeders with hot water and a firm brush (I use one designed for cleaning baby bottles). Wash carefully without soap and use only vinegar if you feel that you must use a chemical cleaner. Rinse with water and dry before adding any more sugar. If you are going on holiday, remove the feeder. The hummingbirds will return when the feeder goes back up.
One can categorise feeders according to the level of the sugar solution.
In tall bottle-like feeders, the level of the solution is above the drinking station. These feeders are still commonly sold (since they are cheap), but, they are not recommended because the solution is more accessible to wasps that compete with hummingbirds. The wasps may even get stuck in the hole making the solution inaccessible to both types of animals. These feeders are often made with pieces of plastic that stop bees and wasps from getting to the solution, but deposits of sugar on bee guards still make other insects a nuisance for hummingbirds. The bee guards are removable and are easy to lose. They are yellow which is a colour that bees see well and the plastic is often not UV stable. These feeders also tend to leak, are much harder to clean and they attract ants. Do yourself a favour and fork out the extra money for a dish-like feeder.
In flat dish-like feeders, the level of the solution is below the drinking stations and therefore do not leak. These latter feeders often have little moats to prevent access by ants. They do not need bee guards because the wasps do not have long enough mouthparts to reach the nectar. I use a HummZinger from Aspects. These well-designed feeders suffer from none of the problems mentioned above.
One can clearly see that the solution in this flat feeder is well below the drinking station.