'Bee hotels' as tools for native pollinator conservation: a premature verdict?

Area of Science:

• Ecology
• Conservation Biology
• Entomology

Background:

• Wild bee populations are declining, causing societal concern.
• Bee hotels (nest boxes) are promoted for conserving above-ground nesting bees, but their efficacy is unproven.
• Most wild bees nest in the ground, not in artificial structures.

Purpose of the Study:

• To evaluate the effectiveness of bee hotels for native bee conservation.
• To assess the occupancy, nesting success, and interactions of native and introduced bees and wasps in bee hotels.
• To identify potential negative impacts of bee hotels on wild native bee populations.

Main Methods:

• A three-year survey of nearly 600 bee hotels in Toronto, Canada.
• Recording and identifying all bees and wasps nesting in or visiting the hotels.
• Analyzing nesting site occupancy, species abundance, parasitism rates, and provisioning behavior.

Main Results:

• Introduced bees nested in 32.9% of sites, comprising 24.6% of all bees and wasps recorded.
• Native bees experienced higher parasitism rates compared to introduced bees.
• Native wasps were most abundant, occupying nearly 75% of bee hotels annually, with introduced wasps showing a significant increase.

Conclusions:

• Current bee hotel initiatives may not benefit native bee populations as intended.
• Bee hotels can be dominated by introduced species and wasps, potentially increasing competition and parasitism for native bees.
• Further research is crucial to understand the complex ecological effects of bee hotels on wild bee conservation.