Honeybees have consequences for foraging bumblebees in Irish heathlands

Area of Science:

• Ecology
• Pollination Biology
• Conservation Science

Background:

• Heather (Calluna vulgaris) is a crucial forage source for wild bumblebees and managed honeybees.
• Increased honeybee presence for honey production may lead to competition for floral resources with native bumblebees.

Purpose of the Study:

• To investigate the impact of increasing honeybee hive density on heathlands.
• To assess effects on honeybee and bumblebee abundance, nectar availability, and bumblebee foraging behavior (size, species composition, flower handling, pollen collection).

Main Methods:

• Field study in upland heathlands examining honeybee hive numbers and their proximity to bumblebee populations.
• Quantified honeybee and bumblebee abundance, nectar availability, bumblebee size, species composition, flower handling times, and pollen collection.

Main Results:

• Higher honeybee hive numbers correlated with increased honeybee abundance but did not affect bumblebee abundance or species dominance.
• Bumblebees exhibited shorter flower handling times and a higher proportion of pollen collectors with increased honeybee presence.
• Bumblebee worker size decreased as the number of honeybee hives increased.

Conclusions:

• Managed honeybees can influence wild bumblebee foraging behavior, even in abundant floral environments.
• Findings suggest potential resource competition affecting bumblebee size and foraging strategies, necessitating consideration in conservation and management plans for both wild and managed bees.