Population persistence of birds affected by species traits under
long-term severe droughts
Abstract
Changing drought regimes is a rising threat to biodiversity, but
reported drought impacts on species varied greatly. Acknowledging the
factors associating with these impacts will bring novel understandings
to species vulnerability to the changes of extreme climatic events, and
facilitate effective mitigation of climate change risks. Based on the
peer-reviewed studies of a well-monitored taxonomic group – birds, we
examined the effects of droughts on population persistence with a focus
on two aspects: population abundance and reproductive success. Responses
of relevant indicators of 172 bird species were extracted across eight
terrestrial biomes, and the droughts triggering these responses were
measured with a climate-comparable and multi-scalar index of drought
severity. A meta-analysis was then conducted for the drought effect on
relative abundance and reproductive success separately, which included
the temporal scale and severity of droughts, as well as biological and
life-history traits of species to explain the effect. We found that
droughts had an overall negative effect on bird abundance and
reproductive success. Apparent abundance generally declined for severe
droughts lasting over a year, while the examined responses varied
greatly due to the disparities of sensitivity and plasticity among
species under droughts occurring at 3-month scale. Drought-induced
declines in abundance were identified for species feeding on
invertebrates, fruits or nectar, and species of a smaller range showed
lower reproductive success during or after droughts. A small clutch size
additionally contributed to the reductions in relative abundance or
reproductive success under severe droughts. Our findings indicate that
bird species with above drought-susceptible traits would confront
greater challenges to population persistence in the regions where the
duration of severe droughts extends. The study also highlights the
necessity of exploring the unknowns that lie in the links between
population persistence and drought responses of bird behaviors,
distribution, morphology and physiology.