Ecological Responses Of The Breeding Jankowski’s Buntings To Environmental Changes

Species with narrow distribution ranges are more susceptible to environmental changes due to the limitation of dispersal capacity,fecundity,and habitat dependence.Jankowski’s Bunting(Emberiza jankowskii)is a small passerine bird mainly breeds in Mongolian steppes of East Asia.The distribution area and population size of the bunting has shrunk sharply.It was listed as an endangered species by the International Union for Conservation of Nature in 2011,but how it responds to environmental changes is unclear.In this paper,we investigated the breeding range and population size of Jankowski’s Bunting;estimated its population dynamics and extinction risk by a population matrix model;predicted its current and future potential distribution changes;determined the responses of their coexisting species to habitat and climatic variables,and studied the effects of habitat characteristics on steppe bird communities.The study confirmed that Jankowski’s Bunting has disappeared from most of its historical breeding ranges.The current suitable breeding habitat is mainly distributed in Zalut Qi and Alukerqin Qi of Inner Mongolia,the size of which is about 280km~2.The breeding population of Jankowski’s Bunting in China is estimated as 9800-12500individuals.Under the current conditions,the reproductive success of Jankowski’s Bunting is lower than that of other buntings with similar body size,and the population growth rate is less than 1(λ=0.8595),indicating that the species cannot maintain stable population growth.The elasticity of Adult survival is 0.73,which means it has a significant effect on the population growth rate.The current status of Jankowski’s Bunting still meets the B2ab standard as an"endangered"species.The distribution of Jankowski’s Bunting has clear responses to four climatic factors:Temperature Seasonality,Precipitation Seasonality,Mean Temperature of Driest Quarter,and Precipitation of Coldest Quarter.The Max Ent model predicts that the current potential suitable climate range of Jankowski’s Bunting is mainly located in northeastern China,and there are small discrete areas of highly suitable in Mongolia.Under different RCP scenarios,the total climatically suitable area of the bunting will increase and new suitable areas will move to the northeast.The changes in the suitable climatic areas were greater under RCP2.6than under RCP8.5,the percentage of change ratio is 72%and 66%,respectively.At the community scale,bird species vary in their response to habitat and climate variables and the abundance of Jankowski’s Bunting showed significant responses to four abiotic variables,including plant height,grassland percentage and annual mean temperature and annual mean precipitation,indicating that this endangered bird has a high niche specialization.The Meadow Bunting,"sister species"of Jankowski’s Bunting,showed similar response patterns to most environmental factors(except annual precipitation and landscape edge density),but had no significant effect,suggesting weak competition exists between the two species.Jankowski’s Bunting displays wide associations with other sympatric steppe bird species,it tends to co-occur with typical grassland birds such as Mongolian lark(the standardized interaction coefficient is 1.37)but avoids co-occurrence with farmland birds such as tree sparrows and magpies(the coefficient is-0.36 and-0.39,respectively).The Markov random field model proves that the co-occurrence patterns of various bird species are dynamically variable along the environmental gradient.The differences in bird assemblages can be explained,in part,by differences in local and landscape-scale habitat features.The responses of the four diversity indices to these predictors were diverse and scale dependent.Species richness and Shannon diversity exhibited similar response,with both being negatively related to bare land(“Estimate”,the median of the posterior distribution of each variable,is-0.04)while being positively related to plant canopy and impervious surface percentage(estimate=0.04).Phylogenetic diversity was positively associated with plant richness(estimate=0.18)while negatively associated with forest percentage and impervious surface percentage(estimate=-0.12 and-0.14,respectively).No statistical evidence for a relationship between functional diversity and any of the variables examined here.Additionally,all the four measures of bird diversity did not peak at intermediate levels of habitat disturbance,these results did not support the intermediate disturbance hypothesis.