Use of human-made nesting structures by wild bees in an urban environment

Abstract

Most bees display an array of strategies for building their nests, and the availability of nesting resources plays a significant role in organizing bee communities. Although urbanization can cause local species extinction, many bee species persist in urbanized areas. We studied the response of a bee community to winter-installed humanmade nesting structures (bee hotels and soil squares, i.e. 0.5 m deep holes filled with soil) in urbanized sites. We investigated the colonization pattern of these structures over two consecutive years to evaluate the effect of age and the type of substrates (e.g. logs, stems) provided on colonization. Overall, we collected 54 species. In the hotels, two gregarious species, Osmia bicornis L. and O. cornuta Latr. dominated the community (over 87 % of the data). Over 2 years, the age of the soil squares did not affect their level of colonization and the same was true for the hotels with respect to O. bicornis and 'other species'. However, O. cornuta occurred less often and raised fewer descendants in 1-year old hotels than in new ones. Bee nesting was not affected by the soil texture and, among above-ground nesting bees, only O. bicornis showed a preference for some substrates, namely Acer sp. and Catalpa sp. In a context of increasing urbanization and declining bee populations, much attention has focused upon improving the floral resources available for bees, while little effort has been paid to nesting resources. Our results indicate that, in addition to floral availability, nesting resources should be taken into account in the development of urban green areas to promote a diverse bee community. Keywords Wild bees Á Nesting resource availability Á Nest-site fidelity Á Phylopatry Á Nest-site selection Á Substrate quality Á Human-made nesting structures Á Urban area This work is dedicated in memoriam of Robert Fonfria.

The proportion of impervious surfaces at the landscape scale structures wild bee assemblages in a densely populated region

“…), might have locally promoted the presence of these species over ground‐nesting species (Fortel et al. ).…”

“…This might also explain why some aboveground-nesting species, such as Hylaeus communis and Megachile willughbiella, are present in urban matrices. On the other hand, some wildlife-friendly practices observed close to our urban sites, such as "hotels" for bees built with bundles of cardboard tubes or reeds (Mader et al 2010), might have locally promoted the presence of these species over ground-nesting species (Fortel et al 2016). Body size and flight abilities are often correlated among bees (Ara ujo et al 2004;Stang et al 2006).…”

Massively Introduced Managed Species and Their Consequences for Plant–Pollinator Interactions

“…Other conservation practices might be developed in cities towards plant and pollinators such as sowing flowering communities and ecological gardening (Blackmore and Goulson, 2014), reduced use of pesticides (Muratet and Fontaine, 2015) or installing nesting habitats for pollinating insects (Fortel et al, 2016). We do not seek to oppose Apis and non-Apis conservation strategies (Aebi et al, 2012), but a priority is to determine the optimal densities of domesticated and wild pollinators to preserve both biodiversity and beekeeping activities.…”

Range expansion of the Asian native giant resin bee Megachile sculpturalis (Hymenoptera, Apoidea, Megachilidae) in France

“…Indeed, M. sculpturalis is a cavity‐nester that uses holes in wood and stems and thus its introductions could result from transportation in wood or other nesting substrates. Moreover, the species has been reported using human‐made nesting structures (“bee hotels”) (Fortel, Henry, Guilbaud, Mouret, & Vaissière, ; Quaranta, Sommaruga, Balzarini, & Felicioli, ). The increasing use of these structures as a conservation tool for bees (MacIvor & Packer, ) could have promoted its spread.…”