Ranking pollen from bee plants according to their protein contribution to honey bees

Abstract

The existing literature classifies bee pollen as “excellent” or “poor” according to protein content. In this research, we ranked bee pollen according to its contribution to bee nutrition, taking into consideration the seasonal variation. We found that the richness in protein content of each single taxon alone is not enough to classify it, as a “good” pollen source, and seasonal variation in vegetation and colony needs should be taken into account. In many cases, bees collected more pollen from plants poorer in protein, which were in total more beneficial to the colony compared to pollen rich in protein, but collected in smaller amounts. We concluded that the amount of the collected pollen was the most important factor and this is relative to the population of the plants at the surrounding area, the flowering period, and the season. The attractiveness of pollen, as indicated by the amount of pollen collected by the bees, was not correlated to the protein content of different taxa. Bees collected pollen from a large number of taxa, but only few of those contributed significantly to their nutritional requirements. We found that only 14 out of 46 pollen taxa included the 88.8% of the total proteins that were available for bees. The crude protein of these “selected” pollen sources ranged from 13.9 to 25.5%. Pollen from plants blooming in spring had higher protein content (20–24.7%) than those from summer (15.1–19.9%) and autumn (19.3–23.1%). The great amount of pollen that honey bees collected in spring and its richness in proteins could explain the strong growth of brood and population during this period.