| Wind energy development has expanded immensely in recent decades throughout the world,and the wind power global capacity exceeded 590 GW in 2019,which was double that in 2015.The use of wind energy is beneficial for reducing carbon emissions,but studies have shown that wind farms can have negative impacts on flying animals.These effects can be assigned to direct and indirect categories:(a)wind farms may negatively impact bats and birds via collisions,where mortality due to collisions with turbines mostly affects soaring and migratory birds;and(b)wind farms indirectly affect birds through related habitat loss,movement barriers,electromagnetic radiation,high noise,and vibration disturbances.Thus,wind farms can lead to impacts in terms of displacement,behavioral changes,and breeding success,which may eventually result in declines in abundance or survival.As a consequence,how to balance the development of wind power and waterbird conservation has become an important issue for biodiversity conservation throughout the world.The Yangtze River Estuary lies on the east coast of China and it is one of the 50 most ecologically sensitive regions in the world due to its biodiversity value and increasing pressures from economic development.Chongming Dongtan,located at the mouth of the Yangtze River,was designated as a Ramsar site in 1998 and it is one of the most important wetlands in this region for waterbird conservation.The dominant groups of waterbirds in Chongming Dongtan are shorebirds(Charadriidae),ducks(Anatidae),egrets/herons(Ardeidae),and gulls(Laridae).At the same time,Chongming Island is rich in wind resources,and the wind power density near the Yangtze River estuary is 300-330 W /?.In order to take advantage of the wind power,two wind farms are built outside Chongming Dongtan National Bird Nature Reserve.The Chongming Dongtan wind farm in China is an ideal study area for examining the effects of a wind farm on the little egret Egretta garzetta(Pelecaniformes),which has been a common ardeid bird species near this wind farm since it was constructed in2008.Firstly,to investigate the effect of Chongming Dongtan wind farm and its surrounding land use types on the distribution and behavior of little egrets near the wind farm,we set up 37 quadrats at the wind farm area and no wind farm area,and calculated the distance from the center of each quadrat to the wind farms and covers of each land use types(aquaculture pond edge,ditch,rice paddy,marsh grassland,marsh open water,river,and others).We surveyed the abundance and behaviors(rest,locomotion and foraging)of little egrets in each quadrat from June to October in 2019.Secondly,to study the collision risk of egrets flying near Chongming Dongtan wind farm,and understand the relationship between risk rate and flight behaviors and environmental variables,we collected the flight behaviors(risky flight,flight direction and flight height)of little egrets and environmental factors(wind speed,rotation and layout)near Chongming Dongtan and Nantong wind farms from August to November 2020.Through the analysis and processing of the data,the following results are obtained:(1)A total of 2839 little egrets were recorded,the average observed abundance was15.073 ± 18.638(mean ± standard deviation)individuals per quadrat.The model averaged coefficients indicated that the abundance of little egrets did not change significantly with the distance to the wind farm.However,aquaculture pond edge cover had a significantly positive relationship with abundance,and marsh open water cover was negatively related to abundance.(2)Rest behavior accounted for 42.4% of all behaviors observed,followed by foraging(37.3%),and locomotion(20.3%).The observed foraging subcategories comprised stand-and-wait(44.3% of foraging behavior),walk slowly(45.1%),and walk quickly(10.5%).The model averaged coefficients showed that locomotion was negatively correlated with river cover,but we found no significant relationships between three behavioral categories and the distance to the wind farm.Among the three foraging subcategories,distance to the wind farm was positively correlated with stand-and-wait and marsh open water cover was negatively correlated with walk quickly.(3)We totally recorded 336 little egrets flying index in the wind farm.The risk index of little egrets passed by the wind farm was 28.7%,and the avoid rate was 71.3%.the most direction of little egrets passing by the wind farm was flying through the wind farm(48.1%),followed by parallel wind farm(31.3%),and the least reverse flight(20.6%).The flying height of egrets passing by the wind farm was mostly below the rotating height of wind turbine blades(93.7%),and no individuals flying above the blades were observed.Based on the average coefficient of the model,when turbines were rotating,the risk rate was significantly lower compared when it wasn't rotating.Furthermore,the frequency of risk situations at Nantong wind farm was significantly higher than that in Chongming Dongtan.The flying direction of passing through the wind farm showed significant higher risk rate than reverse flying. |
PDF Full Text Request