Aarhus Universitets segl

No. 517: The pollen supply of honey bees in Danish landscapes

Dupont, YL, Greve, MB, Kryger, P. 2022. Honningbiernes pollenforsyning i danske landskaber. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 60 s. – Videnskabelig rapport nr. 517, dce2.au.dk/pub/SR517.pdf


Pollen from flowering plants contains protein, fatty acids, vitamins and bioactive substances, and is an important source of nutrition for bees. Honey bees live in large, social colonies, and provision pollen as bee bread in wax combs in the nest, where it is used primarily as larval feed. Pollen is highly variable in quality, in particular in protein content, and the availability, and hence pollen source of a honey bee colony is affected by the landscape surrounding the honey bee hive. Quality of the pollen source influences colony health and winter survival. The aim of the current study was to identify important sources of pollen for honey bees. Specifically, we investigated variation in honey bee pollen sources through the flowering season in different regions and landscape types in Denmark, in order to assess the influence of flowering season and landscape composition on honey bee pollen collection.

Pollen samples from honey bee colonies were collected by volunteer beekeepers from apiaries placed in different landscape types across Denmark. Bee keepers were instructed in sampling bee bread recently collected by honey bees. Bee bread was collected from the combs from the onset of the season (late March/early April in 2020 and late April/early May in 2021) and until early October 2020/2021. In total, 258 bee bread samples were collected from 31 apiaries in 2020 and 53 samples from nine apiaries in 2021. Samples were sent to the pollen laboratory Quality Services International (QSI), and morphologically identified by light microscopy following the standard protocol DIN-Norm 10760. Land use of the landscapes surrounding each experimental apiary was analysed using GIS. The surrounding landscape of an apiary was defined as a three kilometer circle around the apiary, which includes 75 % of honey bee foraging trips (Couvillon et al., 2014). Land use (in ha) was categorized using the basemap classes agriculture, nature, urban, forest, water and other (road, railroad, resource extraction areas, non-categorised).

A total of 105 pollen types were identified to angiosperm family, genus or species. Pollen types included both crops and wild plants. The diversity of pollen, i.e. number of pollen types, was low until late May, increasing until late August, after which it decreased. Only 20 pollen types were represented by more than 1 % of a pollen sample. These were: oilseed rape (Brassica), willow (Salix), white clover (Trifolium repens), fruit trees (Pirus/Prunus), raspberry/bramble (Rubus), maple (Acer), dandelion (Taraxacum), ivy (Hedera), scorpionweed (Phacelia), buttercup family (possibly Clematis (Clematis)), poppy (Papaver), Spanish chestnut (Castanea sativa), yarrow (Achillea), red clover (T. pratense), meadowsweet (Filipendula), horse chestnut (Aesculus), faba bean (Vicia faba), mustard (Sinapis), common heather (Calluna vulgaris), and butterfly bush (Buddleja). A high seasonal variation following the seasonal progression of flowering plants, was found in the pollen sources of honey bees. Furthermore, the pollen source was to some extent affected by composition of the surrounding landscape. However, variation was low in the top 10 pollen types among different landscape types (landscapes dominated by farmland, urban areas, open nature, forest and islands), Pollen samples from landscapes with a high coverage by urban areas, in general, had a higher diversity of pollen types.