Avian responses to an extreme ice storm are determined by a combination of functional traits, behavioural adaptations and habitat modifications

Abstract

The extent to which species' traits, behavior and habitat synergistically determine their response to extreme weather events (EWE) remains poorly understood. By quantifying bird and vegetation assemblages before and after the 2008 ice storm in China, combined with interspecific interactions and foraging behaviours, we disentangled whether storm influences avian reassembly directly via functional traits (i.e. behavioral adaptations), or indirectly via habitat variations. We found that overall species richness decreased, with 20 species detected exclusively before the storm, and eight species detected exclusively after. These shifts in bird relative abundance were linked to habitat preferences, dietary guild and flocking behaviours. For instance, forest specialists at higher trophic levels (e.g. understory-insectivores, woodpeckers and kingfishers) were especially vulnerable, whereas open-habitat generalists (e.g. bulbuls) were set to benefit from potential habitat homogenization. Alongside population fluctuations, we found that community reassembly can be rapidly adjusted via foraging plasticity (i.e. increased flocking propensity and reduced perching height). And changes in preferred habitat corresponded to a variation in bird assemblages and traits, as represented by intact canopy cover and high density of large trees. Accurate predictions of community responses to EWE are crucial to understanding ecosystem disturbances, thus linking species-oriented traits to a coherent analytical framework.

Figure 1

(a,b) Rarefaction curves and estimates of bird species richness during sampling periods pre- and post- storm, at Chebaling, Guandong province, China; (c) Regression plot fitted by Generalized Linear Model with Maximum Likelihood showing the population fluctuation (Log pre-/post-storm) of species; (d) Comparison of five bird species that exhibited significant population change after extreme ice storm; (e–i) Changes in the proportion of relative abundance of bird species grouped by (e) habitat preference, (f) dietary guild, (g) flocking guild, (h) migratory status and (i) human tolerance. The abbreviation refers to: Habitat preference: “edge species (ES)”, “edge-tolerant forest species (ETF)”, “forest specialist (FS)”, “generalist (G)”, “open-habitat species (OS)”; Dietary guilds: “arborous foliage glean insectivore (AFGI)”, “arborous foliage glean insectivore-frugivore (AFGIF)”, “arboreal frugivore–predator (AFP)”, “bark-gleaning insectivore (BGI)”, “miscellaneous insectivore-piscivore (MIP)”, “nectarivores-insectivore-frugivore (NIF)”, “sallying insectivore (SI)”, “terrestrial frugivore (TF)”, “terrestrial insectivore (TI)”, “terrestrial insectivore-frugivore (TIF)”; Flocking guilds: “mixed-species flock participants (FLOCK)”, “Non-flocking species (NON)” and “monospecific flock participants (MONO)”; Migratory status: “passage migrant (P)”, “permanent resident (R)”, “summer visitor (S)” and “winter visitor (W)”; Human tolerance: “moderate susceptibility (MODER)”, “vulnerable to human disturbance (VUL)” and “resistant to human disturbance (RES)”. Level of significance: *P < 0.05; **P < 0.01.

Figure 2

(a) Comparison of five bird species that exhibited significant decline in perching height after the storm; (b,c) Changes in the bird species richness and abundance with different height canopy vegetation (i.e. <3.0 m, 3.0–12.0 m, and >12.0 m) during pre- and post- storm sampling periods. Mean values (±SE) are displayed. Level of significance: *P < 0.05; **P < 0.01.

Figure 3. Ordination biplot of a canonical correspondence analysis (CCA) conducted on bird species as a function of vegetation variables that were highly correlated with the axes (i.e. seven pairs of variables with correlation coefficients >0.30; Table 1).

Refer to Table S1 and Table 1 for abbreviation of bird species and vegetation variable codes. Red color and blue color arrows represent pre- and post- storm values, respectively.