Seasonal variation in pollen and nectar sources of honey bees in Ireland

The floral sources of pollen and nectar used by honey bees in Ireland were studied during 1991-1994 by regular two-weekly sampling of pollen pellets from three colonies at a single site, and pollen and nectar samples from four individual colonies at different sites located in mid-western Ireland. Samples were analysed using dry weight and pollen analysis; relative abundance of pollen types was expressed as a percentage of the total number of pollen grains counted and presented as dominance-diversity curves. At the single site, 76 pollen types were identified and a seasonal variation in the dominance of species was apparent. The diversity of species being foraged reached a maximum during June and July. Native nectariferous species were the most important pollen sources, while pollen was also gathered from introduced and entomophilous/anemophilous species especially during spring and early summer. Trees and shrubs were important pollen sources early in the year while herbs and shrubs increased in importance during summer and autumn. A total of 92 pollen types were identified in the pollen and nectar samples at four different sites and this indicates the diversity of plant species foraged by honey bees and the importance of different species as pollen sources, nectar sources or pollen and nectar sources. Honey bee preferences for certain species and individual colony preferences are discussed.