As with all creatures, good nutrition is very important to a colony of bees. Many beekeepers only look at the amount of liquid stores a colony has, but pollen is equally important, yet often ignored. A lack of liquid stores can lead to starvation in both summer and winter, but a shortage of pollen can have a serious effect for some time, as poorly nourished larvae can result in poorly performing or unhealthy adults.

As a beekeeper, it is imortant to “read” a colony, because it is telling you something all the time. On each inspection, get into the habit of looking into a few cells where there are freshly hatched larvae, around 4-5 days from egg laying. If there is plenty of food coming in, the larvae will be in a big puddle of brood food, but if there is little food coming in, the bottoms of the cells will be almost dry. I wish this sort of observation was taught more by teachers.

Pollen varies in constituents depending on the source and it is generally accepted that a wide variety results in healthier colonies. When inspecting colonies have a look at the color of pollen. The greater the variation of colors, the greater the diversity of sources. Sometimes when inspecting a number of colonies in the same apiary on the same day, you can see some colonies that have largely one color of pollen, suggesting the bees have become locked onto one source, yet other colonies will have a variety of colors.

Poor nutrition doesn’t always mean a shortage of forage, but can be because the ratio between nurse bees and larvae is low, such as you get in the spring when a colony is building up, or if a nucleus is made up with an imbalance of bees.

Colonies that suffer from poor nutrition become susceptible to disease, chalk brood and European Foul Brood (EFB) in particular. Both are often more of a problem in spring, due to the shortage of nurse bees to feed the larvae.

“Fat Bees Skinny Bees”. This is a brilliant downloadable publication that is effectively a manual on Bee Nutrition. It was written by Doug Somerville for the Rural Industries Research and Development Corporation (RIRDC), Australia. At one time it was free, but I see it is now chargeable.
Honey Bee Nutrition. “Honey bee Nutrition and Supplementary Feeding” is a downloadable Australian leaflet written by Doug Somerville and published by the New South Wales Dept of Agriculture. As the introduction says “This agnote is written to give beekeepers an overview of honeybee nutritional requirements and the role of various carbohydrate and protein supplements in the management of honeybee colonies.” If you allow for the items appropriate for Australia I found this to be a very useful and easily understood paper.
There is much more information on the internet and I suggest a search. The principle is the same, all you need do is take the information in context with your own location.