Hotels are usually built for travellers, but some are designed for creatures no bigger than your thumb. Scientists and conservationists have spent years creating these miniature refuges for wild bees in the form of small nesting structures fitted with narrow tunnels that mimic the hollow stems and cavities many solitary bee species naturally use to lay their eggs. Hoping they could provide additional nesting spaces in increasingly urban landscapes, Canadian researcher J. Scott MacIvor installed 200 bee hotels across a city and monitored them for three years. What began as a simple conservation experiment soon uncovered an entire hidden community of insects, prompting researchers to rethink how artificial nesting sites influence pollinators and urban biodiversity.
Why scientists are building hotels for bees
When most people think of bees, they picture honey bees living in bustling hives. In reality, honey bees make up only a small fraction of the world’s bee diversity. Around 90% of the roughly 20,000 known bee species are solitary, with each female building and provisioning her own nest without the help of a queen or worker bees.Many of these solitary species nest inside hollow plant stems, beetle burrows in dead wood and other natural cavities. However, urban development, intensive landscaping and the removal of dead wood have reduced these nesting opportunities in many places. Bee hotels were developed to replace some of this lost habitat by providing carefully sized tunnels where cavity-nesting species, including mason bees and leafcutter bees, can lay their eggs. Unlike honey bee hives, these structures are not colonies but collections of individual nesting chambers, each occupied by a single female and her developing offspring.Most bee hotels are made from untreated blocks of hardwood drilled with narrow holes of different diameters or bundles of replaceable paper or cardboard tubes housed inside a protective frame. Each tunnel is sealed at one end and left open at the other, allowing a solitary female bee to lay an egg, leave behind a ball of pollen and nectar for the developing larva, seal the chamber with mud or leaves, and repeat the process until the tunnel is full. In the wild, these bees would normally use hollow stems, beetle burrows or natural cracks in dead wood to do the same.At the time MacIvor began his research, bee hotels were already being widely promoted as a simple way to help declining pollinators, but there was surprisingly little scientific evidence showing how well they actually worked for native bees. That gap in knowledge became the focus of his study.
A three-year experiment with 200 bee hotels
To find out whether bee hotels genuinely support native pollinators, urban ecologist J. Scott MacIvor and co-author Laurence Packer installed around 200 bee hotels each year across Toronto and the surrounding region, monitoring them over three consecutive years.Published in PLOS ONE, the study examined nearly 600 bee hotel deployments and recorded more than 27,000 emerging bees and wasps. Rather than simply counting how many bees arrived, the researchers identified every occupant, compared native and introduced species, documented parasites and assessed which species occupied the hotels and how these artificial nesting sites affected native bee communities.The bee hotels soon proved to be much more than homes for solitary bees. Native bees did use the nesting tunnels, but they shared them with a surprising variety of other insects. Native wasps occupied nearly three-quarters of the hotels each year, while introduced bee species were also common. Ants, spiders and parasitic insects frequently appeared, turning the structures into thriving miniature ecosystems rather than single-species habitats.The findings suggested that bee hotels can influence entire insect communities, offering researchers a rare glimpse into the complex relationships unfolding inside these artificial nesting sites.
What the study revealed about biodiversity
The research did not conclude that bee hotels are inherently harmful. Instead, it showed that their ecological effects are far more complex than many people had assumed.The researchers wrote, “Altogether, our study findings show that bee hotels appear to differentially augment populations of wasps rather than those of native bees.” They also noted that the findings “highlight a need for increased study of bee hotels and their associated impact upon bee biodiversity and pollination in the urban setting.”Rather than providing a simple conservation fix, bee hotels can influence which species occupy an area, how insects compete for nesting space and how urban ecosystems function over time.
“If you build it, they might come”
MacIvor has consistently argued that the findings should not discourage people from supporting native bees, but instead encourage better-designed conservation efforts.Reflecting on the study, he said, “If you build the nest box, they might come. They might not. Or they might come next year.” His point was that bee hotels should be treated as carefully managed conservation tools rather than guaranteed solutions for declining pollinators.Subsequent studies have refined the best practices for bee hotels, recommending untreated hardwood, appropriately sized nesting tunnels, regular cleaning and thoughtful placement to maximise benefits for cavity-nesting native bees while reducing opportunities for parasites and disease.
Bee hotels are only part of the solution
The study also highlights an important limitation. Most native bee species nest in the ground rather than in wood or hollow stems, meaning bee hotels can benefit only a minority of bee species. Ground-nesting bees instead depend on healthy soils, flowering plants and undisturbed habitats.For that reason, conservationists view bee hotels as just one piece of a much larger strategy. Protecting native wildflowers, reducing pesticide use, preserving dead wood and maintaining natural habitats remain just as important for supporting healthy pollinator populations.Bee hotels may never support every bee species, but they have given scientists an extraordinary window into the hidden lives of pollinators. In doing so, they have shown that even the smallest conservation projects can reveal new insights into biodiversity and the intricate web of life that supports our ecosystems.
