Explaining the birds and the bees: deriving habitat restoration targets from multi‐species occupancy models

Riparian corridors can be highly biodiverse but are often degraded by human activities, and are therefore frequent targets of restoration actions. Yet managers often lack clear guidance on how to conserve or restore riparian vegetation structure and composition to promote wildlife biodiversity, due to the difficulty of balancing the needs of multiple species and taxonomic groups. We used independent multi‐species occupancy models to assess the response of riparian bird and bumble bee assemblages, respectively, to variation in vegetation structure and composition in montane riparian corridors. We sought to identify vegetation characteristics associated with relatively high richness across each taxonomic group to define target conditions for habitat restoration. Riparian bird occupancy increased with more willow (Salix spp.) cover and less overstory cover, while bumble bee occupancy increased with greater flowering plant richness, more forb cover, and less shrub cover. Relatively distinct habitat preferences of bumble bees and riparian birds emphasize the value of managing for habitat heterogeneity to promote biodiversity across multiple taxonomic groups. Multi‐species modeling distills the responses of numerous species down to a single estimate of a covariate effect for an assemblage of species and can provide land managers with empirically derived targets for habitat restoration that will benefit many species. Riparian corridors are important conservation targets because they support diverse plant (Naiman et al. 1993) and animal (Knopf et al. 1988) communities and contribute to regional biodiversity by hosting species absent from upland areas (Sabo et al. 2005). In response to pervasive loss and degradation of riparian habitats worldwide, science‐based approaches to riparian restoration (Goodwin et al. 1997) have aimed to return degraded ecosystems to historical or reference conditions (White and Walker 1997). Defining target conditions for riparian restoration has been a challenge for land managers (van Diggelen et al. 2001). Where improving wildlife habitat is a restoration objective, a common approach is to describe habitat conditions elsewhere that support desired wildlife populations, and then replicate those conditions through habitat manipulation (Dumroese et al. 2015). Yet different wildlife species have unique habitat needs, potentially yielding an intractable number of species‐specific restoration prescriptions that may not be mutually compatible (Mac Nally et al. 2002, White et al. 2013). Managers therefore must often make difficult choices