A standardised protocol for sampling cavity-nesting Hymenoptera using trap nests

Hymenoptera are among the most important members of temperate ecosystems, both for their contribution to ecosystem services and their role in overall ecosystem functioning. While they have received considerable research attention due to their ecological significance and recent declines, substantial knowledge gaps remain regarding their ecology, phenology, and population trajectories. Trap nests are a popular sampling tool for cavity-nesting Hymenoptera, offering excellent potential to fill these knowledge gaps by simultaneously providing data on species-abundance and key ecological, phenological, and behavioural processes. Trap nests also serve as an excellent tool for monitoring environmental change, habitat restoration efforts, and other interventions. However, their use has not yet been standardised, limiting data sharing and comparability between studies. Here, we introduce the first step-by-step protocol for producing and implementing trap nests, available in its entirety via protocols.io. With this protocol and the provided supplementary resources, we aim to promote the use of trap nests and facilitate the standardisation of cavity-nesting Hymenoptera data collection, which is essential for advancing research and developing conservation measures effectively.