Pollen sources for honeybees in Israel: Source, periods of shortage, and influence on population growth

Abstract

The nutritional demands of honeybees are met by two plant-produced components: nectar and pollen, the contents of which vary among floral sources. In Israel, there is an extraordinary richness in plant species, and one of the dominant insect pollinators is the honeybee (Apis mellifera L.). July to February is characterized as a period of low flower abundance for local species in general and for bee forage plants in particular. In this study, we monitored the amount and number of pollen sources collected by honeybees, and where possible also identified the plant source of pollen, in four geographically distinct sites in Israel. We also assessed honeybee colonies (population level, sealed brood area, and pollen and honey stores) and studied the effect of pollen levels on population growth. Our results show that peak pollen-collection times differ according to site. The number of pollen sources from trapped pollen pellets varied during the year, between sites, and between colonies in the same site, and ranged between 5 and 20 plant species per sampling date per site. The most abundant pollen source in each sample comprised between 22 and 94% of the pollen pellets. There were only a few cases in which pollen was collected from fewer than five or more than nine plants in each colony's sample. Thus, colonies seem to specialize in only a small number of species of the available flora. Overall, in all sites, the daily amount of pollen collected was significantly correlated with sealed brood and pollen store areas.