Foraging distances, habitat preferences and seasonal colony performance of honeybees in Central European forest landscapes

1. Unmanaged forest is considered as native habitat of the Western honeybee Apis mellifera and is assumed to provide important pollen and nectar sources. However, resource supply might be spatially and temporally restricted in managed forests and landscape-scale studies in European forest regions are currently lacking. 2. Capitalizing on a unique communication behaviour, the waggle dance, we investigated honeybee foraging in a deciduous forest region in southern Germany. We analysed 2022 waggle dances performed by bees of 12 colonies placed in the centre of landscapes with varying degree of forest cover (50%-99% at a 2-km radius) from March to August 2019, thereby identifying foraging distances and habitat preferences over almost an entire foraging season. By connecting dance information with colony weight recordings, we assessed the role of landscape composition and the contribution of different habitat types to colony weight gain. 3. Foraging distances generally increased with the amount of forest in the surrounding landscape pointing to inferior food resources in the forest. Yet, this effect strongly depended on the season and was more pronounced for pollen than for nectar foraging. Even though colonies in forest-dominated landscapes had to fly further, colony weight was not significantly affected by forest cover. 4. Compared to expectations based on the proportions of different habitats, colonies foraged more frequently in grassland and cropland than in deciduous and coniferous forests, with late summer being an especially difficult period for pollen foraging in forests. During a phase of colony weight gain in early summer, the use of forests for nectar/honeydew foraging was close to the expectation, highlighting forests as an important complementary source of carbohydrates during short periods of the year. 5. Policy implication. The ecological and economic value of managed forest as habitat for honeybees could be significantly increased by the continuous provision of floral resources, especially for pollen foraging. Therefore, we recommend diversifying forest stands with insect-pollinated trees, permitting secondary successions in forest gaps, and at larger scales, creating forest landscapes with high habitat diversity. This will not only help native, wild-living honeybees and beekeepers' colonies residing in forest areas but will also foster social bees in general.

Automated summary

This study investigated honeybee foraging in a deciduous forest region in southern Germany by observing waggle dances. The foraging distances of bees were found to be related to forest cover, but varied depending on the season and food type. Although bees in forest-dominated landscapes had to fly further, forest cover did not significantly affect colony weight. Pollen foraging in forests was more difficult in late summer, while nectar/honeydew foraging in forests aligned with expectations in early summer.