Food resources and vegetation structure mediate climatic effects on species richness of birds

Abstract

Aim Climate is widely recognized as a major predictor of species richness patterns along large‐scale environmental gradients. Nevertheless, the mechanisms by which climate influences species richness are still a matter of debate. We disentangle whether climate influences species richness of birds directly via physiological limitations or indirectly via vegetation structure or the availability of food resources. Location Mount Kilimanjaro, Tanzania. Methods We recorded bird species richness along an elevational gradient from 870 to 4550 m a.s.l. We quantified local climatic conditions, vegetation structure and the availability of food resources, and applied path analysis to disentangle their direct and indirect effects on species richness of all birds, frugivores and insectivores. Results Overall, we recorded 2945 individuals from 114 bird species. Species richness of all birds was closely correlated with temperature, vegetation structure and invertebrate biomass and both direct and indirect (via vegetation structure and availability of food resources) climatic effects were important for the diversity of the whole, trophically heterogeneous bird community. The species richness of insectivorous birds was linked to vegetation structure and invertebrate biomass, while the richness of frugivores was strongly associated with fruit abundance. Climatic factors influenced bird species richness of both avian feeding guilds exclusively indirectly via vegetation structure and availability of food resources. Main conclusions We reveal the importance of trophic interactions for generating species richness patterns along large‐scale environmental gradients. Our results challenge the general assumption that temperature and water availability influence species richness mostly directly, and underscore the importance of vegetation structure and the availability of food resources as principal mediators of climatic effects on species richness patterns on macroecological scales.

Road induced edge effects on a forest bird community in tropical Asia

“…Vegetation structure had the strongest effect on species richness and abundance of insectivorous birds, with higher complexity of vegetation structure positively associated with species richness and abundance of most insectivores, especially bark-gleaning, sallying, terrestrial, and understory insectivores (Ferger et al 2014;Mammides et al 2015). In our study area, vegetation structure within 100 m from the edge was generally simpler, with only one or two layers of particularly dense small trees and saplings and a greater cover of vegetation near ground level.…”

“…The reduced layers of small trees may limit shelter and foraging substrates for sallying and understory insectivores, such as the Black-naped Monarch (Hypothymis azurea) and Orange-breasted Trogon (Harpactes oreskios); whereas the greater cover at ground level may be an obstacle to terrestrial insectivores such as the Puff-throated Babbler (Pellorneum ruficeps). In contrast, the forest interior had a more complex vegetation structure, with a higher basal area, higher density of larger trees, more vegetation layers, and less ground cover, which probably provided more diverse arthropod resources and foraging habitats (Ferger et al 2014). Bark-gleaning woodpeckers and understory insectivores (trogons and kingfishers) also were negatively affected by the edge.…”

“…Slightly higher richness and abundance of frugivores in the forest interior may be associated with a higher basal area and density of large trees (Deikumah et al 2014) and more potential food resources (Ferger et al 2014). Higher basal area, density of large trees and vegetation cover at the canopy level of our forest interior could provide greater fruit availability (Lindenmayer et al 2012).…”

Bird Communities In Seblat Nature Recreation Park (SNRP) North Bengkulu, Bengkulu

“…HS2 had complex vegetation, offering more niches and higher levels of plant. It contributed to more bird species diversity (Pearman, 2002;Miller et al, 2004;Ferger et al, 2014). Feet al, 2014).…”

High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

“…By stepwise refitting, we simplified the SEMs, removing non-significant links conditional on the model fit, i.e. assessed by the x 2 test, CFI, and RMSA, being satisfied [60,61]. As the two final SEMs differ in the number of climate variables included (see Results; figure 2), we cannot use the x 2 test, CFI, and RMSA measures of fit for comparison of model fit among the final SEM models.…”