Foraging Habitat Selection And Space Utilization Pattern Of Overwintering Black-Necked Crane In The Farming Area Surrounding The Caohai Waterland,Guizhou Province

Caohai wetland(Caohai National Nature Reserve)in Guizhou Province is one of the important wintering areas for the Eastern population of Black-necked Crane(Grus nigricollis).Every year,more than 1500 Black-necked Cranes fly to the Caohai wetland for overwintering.Therefore,the selection and utilization of wintering foraging areas are the key factors for the survival of Black-necked Crane in the winter.To explore the selectivity of Wintering Black-necked Crane to foraging sites in farming area is also the basis for habitat management and conservation for it.The Black-necked Crane has a habit of using human farming land to find food.At the same time,because the Caohai of Guizhou is close to Weining County,the phenomenon of people and birds competing for the land is very serious.A series of recent measures,such as the construction of the road around the lake,the return of farmland to the lake,and the rise of water level,have led to the further atrophy and degradation of the wetland habitat of the lake,which further increases the dependence of the Black-necked Crane on the food-seeking land in the farming area.However,due to the urban.The traditional farmland around Caohai is also shrinking and decreasing due to the expansion and the change of farming methods.Previous studies only focused on the foraging land selection of Black-necked Crane in the wetland lakeside area,but not in the farming area.Therefore,in order to find out how the Black-necked Crane chooses the foraging land in the peripheral farming area,and what kind of spatial relationship exists between the foraging land and the farming land,so as to better protect the foraging land of the Black-necked Crane in winter and ensure the survival of the overwintering population,this study,in the winter of 2016-2019,combined with the spatial analysis methods such as direct observation method,quadrat investigation method and spot pattern analysis,etc.The pattern of foraging land selection and spatial utilization of the Black-necked Crane over the winter was studied.1.The Black-necked Crane in Caohai of Guizhou Province has a feeding utilization ratio in the agricultural land and likes to forage for the remaining potato crops in the agricultural land.There was a significant correlation between the number and area proportion of cultivated crops and the number and area proportion of cultivated crops used by the Black-necked Crane in the study area,among which the potato field accounted for 88.81%of the total area of foraging land.2.Food factors and interference factors are the important factors that affect the selection of forage land for Black-necked Crane in Caohai of Guizhou Province.The cumulative contribution rate of the first four characteristic roots in PCA has exceeded65.83%.It can basically reflect the main influencing factors of foraging land selection in farming areas.Among them,the food factor is the first principal component,and the larger load factor is farming method(-0.875)and crop allowance(0.771);the interference factor includes the second principal component and the third principal component,and the larger load factor is distance from residential area(0.678)and road(0.698);the terrain factor is the fourth principal component,and the larger load factor is slope direction(0.639).The selection coefficient of Vanderploeg and Scavia showed that the Black-necked Crane tended to choose the farmland with semi-shade and semi-sunny slope,50m-100m away from the highway,100m-500m away from the residential area,and the crop surplus was more than 500g/m~2,which was not plowed by machinery.3.As time goes on,the influence of the main factors on the selection of foraging sites is also changing.The amount of food decreased linearly with time.In the early stage,the selection of foraging land was mainly influenced by the interference factors.At this time,how far away the selection of foraging land was from the interference of roads and residential areas;in the middle and late stage,the influence of food factors was stronger than the interference factors.In this stage,the selection of foraging land mostly chose the farmland with a large amount of food,which was closer to the roads and residential areas than in the early stage.4.The spatial pattern of the foraging ground of the domestic crane and the clustered crane showed aggregation distribution,but the aggregation intensity of the domestic crane was weaker than that of the clustered crane.5.The foraging land of the Black-necked Crane is positively correlated with the Caohai farming land,and the spatial aggregation degree is the strongest at 3200m.The foraging of the Black-necked Crane has gradually transited from the sedge meadow around the lakeside wetland to the farming area farther away from Caohai Lake.Through spatial analysis,the cultivated land suitable for foraging was divided into different levels of protected areas,priority protection areas,and secondary protection areas.The key protected areas are mainly Caojiadafen and Guojiafen,which are mainly the existing foraging areas;the secondary protected areas are Suohuangcang and Zhaojiahaizi,which are mainly close to the night habitat,with a small number of confirmed foraging areas around and a large area of continuous distribution of cultivated land;the other cultivated land is not located due to human interference,discontinuous distribution and other reasons.Within the scope of priority protection.