| The Black-necked crane(Grus nigricollis)is a large-scale wading bird,and its population dynamics have been widely concerned.The Caohai Wetland in Weining,Guizhou,is one of the largest wintering sites in the eastern part of the black-necked crane.More than 1,500 have been wintering here in the past five years.Caohai is close to Weining County,with serious land competition between humans and birds,and measures such as building roads around the lake and returning farmland to lakes have accelerated urbanization and increased land use intensity,forcing the range of the wintering habitat of Caohai black-necked cranes to be continuously squeezed,The area of the wintering area is gradually shrinking and gradually changing,posing a serious threat to the survival of the wintering black-necked crane population in Caohai.To this end,in order to clarify the population dynamics of wintering black-necked cranes in Caohai and the law of habitat utilization changes,and to promote the conservation and management of wintering black-necked cranes in Caohai,this study uses the principles of landscape ecology,and through field investigation and data tracking methods,The population dynamics and landscape pattern changes of the overwintering black-necked crane in Caohai have been studied,and the results are as follows:(1)The population of black-necked cranes overwintering in Caohai has changed greatly from 1975 to 2021,showing an overall increasing trend.The number of black-necked cranes was in a rapid recovery period from 1975 to 1984(SD=111.68),a stable period from 1985 to early 1990(SD=39.71),a stable growth period from1991 to 2000(SD=104.93),the first in 2001-2006 The second surge period(SD=248.01),the first period of volatility in 2006-2011(SD=109.71),the second period of surge in 2011-2016(SD=375.03),the second period of volatility in2016-2021(SD=147.5).Since 2015,the population of overwintering black-necked cranes in Caohai has remained at around 1500-2000.(2)The habitat of the wintering black-necked crane in Caohai in the 1980s was widely distributed around the coastal wetlands of Caohai Lake.From 2010 to the present,the night habitat has been fixed in the 7 marshes of Hu Yelin,Kangjiahaizi,Wangjiayuanzi,Liujiaxiang,Yangguanshan,Wenjiatun,and Wujiayantou.After 2015,the population density in Wangjiayuan(225 animals),Liujiaxiang(267 animals),Wenjiatun(561 animals),and Yangguanshan(303 animals)was increasing.After the21st century,the lakeshore beaches around the north and east of Caohai Lake and the surrounding farmland have lost their function as a habitat for black-necked cranes due to human interference and severe fragmentation,causing black-necked cranes to travel farther from Caohai.Foraging on farmland in the northwest,southwest and south.(3)From 1980 to 2020,the land use of Caohai has changed significantly.Among them,the most dynamic changes in land use are construction land(537.94%),forest land(5.01%),water body(4.91%),and the remaining land use types have developed steadily.The area of construction land,water bodies and forest land has increased significantly,and the area of arable land and grassland has decreased,and most of the reduced area of arable land and grassland has been converted to construction land.In the future,the area of construction land in 2030 will be 59.5 km2,and the area of water bodies will be 36.47 km2,and the area of construction land and water bodies will continue to grow from 2030 to 2060.(4)From 1980 to 2020,the dynamic changes of black-necked crane populations have a greater correlation with land use types,and the order of correlation is as follows:construction land>water body>forest land>cultivated land>grassland>unused land.The correlation coefficients are:0.9320,0.8083,0.7829,0.7684,0.7672,0.6398.The number of historical distribution points of the overwintering population of Caohai black-necked cranes is most affected by the changes in the area of construction land,showing a positive correlation(R~2=0.993).The number of black-necked cranes has a greater degree of correlation with social environmental factors.The order of correlation is as follows:total grain output>total population>number of industrial enterprises>annual average temperature>annual rainfall>primary industry added value>secondary industry added value.The correlation coefficients are:0.8119,0.8059,0.7727,0.7671,0.7467,0.6996,0.6331.The total grain output has the greatest impact on the number of black-necked cranes(R~2=0.719).(5)Based on the assumption that the ratio of the tibia to the tarsals of adult cranes is basically constant,the ratio of the tibia to the tarsals of the black-necked cranes and the wading of black-necked cranes are calculated using 1288 individual photographs of black-necked cranes.Calculate the wading depth projection value of the tarsals submerged in the water based on the ratio of the shin and the tarsal plantars exposed to the surface of the water,and use the measured values to calculate the accurate depth range of the black-necked cranes inhabiting and wading.The results showed that 89.92%of the wading depths were within(0,20)cm,76.11%of the wading depths were within(0,10]cm,and 49.04%of the wading depths were within(0,5)cm,indicating overwintering Black-necked cranes prefer(0,10]cm shallow water swamps for food or night habitation. |
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