Foraging height and landscape context predict the relative abundance of bird species in urban vegetation patches

Abstract

In Australian urban environments, revegetation and vegetation restoration are increasingly utilized conservation actions. Simple methods that help assess the utility of urban vegetation for bird species will help direct this effort for bird conservation purposes. We therefore examine whether ecological principles can be used to predict, a priori, the relative abundance of different bird species in urban vegetation. Our model proposes that a bird species will be in greater abundance where vegetation structure better reflects its foraging height requirements, and this relationship will be moderated by the landscape context of the patch. To quantify and test this model, we created an index to rank existing and revegetated urban vegetation sites in order of greatest expected abundance for each of 30 bird species. We tested this model, alongside two simpler models which consider landscape context and foraging height preferences alone, using bird abundance data from 20 woodland remnants and 20 revegetated sites in Brisbane, Australia. From these bird abundance data, we calculated the relative abundance of each species between the top-ranking sites and lowest-ranking sites. The model which incorporated both foraging height requirements and landscape context made predictions that were positively correlated with the data for 77% of species in remnant vegetation and 67% in revegetation. The results varied across species groups; for example, we achieved lower predictive success for canopy foraging species in the less mature revegetation sites. Overall, this model provided a reasonable level of predictive accuracy despite the diversity of factors which can influence species occurrence in urban landscapes. The model is generic and, subject to further testing, can be used to examine the effect of manipulating vegetation structure and landscape context on the abundance of different bird species in urban vegetation. This could provide a cost-effective tool for directing urban restoration and revegetation efforts.

Assessing the impact of revegetation and weed control on urban sensitive bird species

“…But at a local level, the quality of urban greenspaces also impacts the abundance of bird species present within urban centers. Therefore, restoring urban greenspaces is an important component of conserving urban biodiversity by providing refugia, although currently we are not maximizing the conservation impact of these areas for species which rely on these areas the most (Fernández‐Juricic & Jokimäki, ; Shanahan, Miller, et al., ; Shanahan, Possingham, et al., ).…”

“…Management history for each location was collected from project participants during a prior study (Shanahan, Miller, et al., ; Shanahan, Possingham, et al., ), and all 70 sites were surveyed for vegetation structure and composition. We used a space‐for‐time substitution method to evaluate the impact of each restoration action compared to its counterfactual (Pickett, ).…”

“…The impacts of fragmentation and degradation due to urbanization on biodiversity have been documented widely (Venter et al., ; Zipkin, Dewan, & Royle, ), including in green spaces within urban areas (Fernández‐Juricic & Jokimäki, ). Bird species richness and abundance within the broader landscape context have been shown to be negatively affected by the loss and fragmentation of green spaces (Crooks, ; Shanahan, Possingham, et al., ; Zipkin et al., ). Therefore, restored urban greenspaces can benefit urban areas as well as the broader landscape, possibly by providing refugia for urban biodiversity (Fernández‐Juricic & Jokimäki, ; Shanahan, Miller, et al., ; Shanahan, Possingham, et al., ).…”

Creating vegetation density profiles for a diverse range of ecological habitats using terrestrial laser scanning

“…Density profiles could also be utilised in studies of how vegetation structure directly affects the habitat suitability for different species (James & Wamer 1982;Gunnarsson 1990). For example, different species may be sensitive to the structure or cover at a certain preferred height in the canopy (Shanahan et al 2011), and density profiles allow researchers to focus on the cover at different heights for different species. Density profiles could also be used to assess bushfire hazard, for example, by detecting 'ladder fuels' that allow ground fires to reach the upper canopy (Lefsky et al 2002).…”

Water availability drives aboveground biomass and bird richness in forest restoration plantings to achieve carbon and biodiversity cobenefits

“…Woodland and forest birds are declining worldwide, including in Australian eucalypt woodlands (Ford, ), and birds with particular life history traits are more at risk of decline in fragmented and degraded landscapes than other groups of bird species (Barnagaud, Barbaro, Papaïx, Deconchat, & Brockerhoff, ; Joyce, Barnes, Possingham, & Van Rensburg, ; Lindenmayer, Lane, et al, ). Understorey‐ and ground‐nesting birds are more susceptible to decline because of their dependence on understorey vegetation for nesting and shelter, and the widespread loss and degradation of the grass/tussock and shrub/sapling layers in agricultural landscapes that are subject to livestock grazing (Martin & McIntyre, ; Martin & Possingham, ; Shanahan, Possingham, & Martin, ). Loss and degradation of understorey vegetation has also been associated with declines in insectivorous birds because of reductions in insect diversity (Barton, Sato, Kay, Florance, & Lindenmayer, ; Gibb & Cunningham, ; White, Antos, Fitzsimons, & Palmer, ).…”