Foraging habitat selection of overwintering Black-necked Cranes in the farming area surrounding the Caohai Wetland, Guizhou Province, China

Background: Understanding how overwintering birds choose foraging habitats is very important for conservation management. The overwintering Black-necked Crane(Grus nigricollis) feeds on crop remains in farmlands;thus, reasonable conservation management of this type of farmland that surrounds wetlands is critical for the overwintering populations of the Black-necked Crane;however, it is not clear how the Black-necked Crane chooses the foraging land in the farmland.Methods: A thorough field positioning survey of all foraging sites in farmland areas around the Caohai Wetland and a-sampling analysis of habitat selection by the Black-necked Crane were conducted during the winters from 20162017 and 2017-2018.Results: Multiple factors contributed to the selection of foraging habitat in farmlands, i.e., food factors(crop remains and tillage methods) > human disturbance factors(distance to road and settlement) > topography factors(slope aspect), listed according to the strength of influence. Additionally, Black-necked Cranes tend to choose farmland sites where there was no machine tillage, the crop remains were > 500 g/m^2, the distance to residences ranged from 100 to 500 m, the distance to roads ranged from 50 to 100 m, and the slopes exhibited western or eastern aspects. As the winters progressed, the volume of the edible crop remains declined, and the influences of the other main factors also changed, i.e., the factors of human disturbance(distance to road and settlement) became less important, while the effect of the food factor(crop remains) was strengthened. Thus, the foraging sites near the road became more important.Conclusion: The farming area surrounding the Caohai Wetland is very important for the overwintering Black-necked Crane. Food factors and human disturbance factors are the main factors that influence the choice of feeding ground.

Population dynamics and habitat use of the Black-necked Crane (Grus nigricollis) in the Yarlung Tsangpo River basin, Tibet, China

Background:The Black-necked Crane (Grus nigricollis)is an internationally threatened crane living on the plateau, mainly in winter, in the Yarlung Tsangpo River basin in Tibet,western China. In the past five years,some economic development projects have been conducted in this area,posing potential threats to the wintering populations of the cranes and their habitats. Therefore, the current population dynamics of wintering Black-necked Cranes and habitat suitability in the Yarlung Tsangpo River basin were investigated. Methods: Twenty counties were surveyed using the line transect method in December 2017 and January 2018, and we recorded the location,flock size,number of individuals,habitat types and presence of human disturbance in which they occurred.We compared the results from the middle wintering period in this survey with those from 2014. Results: The highest number of cranes recorded was 8291,and the results showed that the cranes were mainly distributed in Lhaze, Namling, Samzhubze, and Lhunzub.A total of 577 and 495 flocks were recorded in the early and middle wintering periods, respectively. In the early wintering period,there were signi ficant differences in the number of individuals across the di fferent habitats,with crop stubble land and plowed land representing more than 30% of the total habitat utilization.In the middle wintering period, there were also signi ficant differences in the number of individuals, and the utilization of crop stubble land represented over 60% of the total. Conclusions: Wintering Black-necked Cranes mainly fed on spilled grains in stubble habitat after harvest. In the middle wintering period, some of the farmlands were plowed and irrigated,which resulted in food shortages in these areas,and the cranes tended to gather in mixed flocks of large size instead of as a single family.There were still considerable regional wintering populations decreases in Quxu,Nedong,and Sakya in 2018 compared with 2014,and these decreases were mainly due to some recently emerging threats,including farmlands being converted into areas of greenhouse cultivation,highway and railway construction, river dredging,the rapid development of the manufacturing and mining industries,and the lack of protection of important wintering sites.

Sequential vigilance is unpredictable in reproductive Black-necked Cranes

Background:Vigilance refers to the behavior of animals scanning their surroundings with a main purpose of antipredation.Whether vigilance can serve the function of anti-predation depends on its unpredictability,meaning instantaneous randomness,sequential randomness,and independence,the three assumptions from Pulliam model(J Theor Biol 38:419,1973).Here we tested two of these three assumptions in reproductive Black-necked Cranes(Grus nigricollis) in Tibetan Plateau:instantaneous randomness and sequential randomness.Methods:Observations were carried out in July and September of 2014,July and August in 2017 in Selincuo National Nature Reserve,Tibet,with the help of focal sampling method.For instantaneous randomness,we used Kolmogorov–Smirnov test for its negative exponential distribution;for sequential randomness,we used Run test,correlation analysis,and generalized linear model to see if an inter-scan and its previous scan were correlated.Results:Not similar to some recent studies,we did not find a significant predictable vigilance in this crane.Most inter-scan intervals(86/100,86.0%) passed negative exponential distribution test,meaning vigilance sequences with instantaneous randomness;most inter-scan intervals(91/100,91.0%) passed sequential random test,showing vigilance sequences were random organized.Conclusion:Our results suggest that keeping a vigilance pattern with unpredictability is beneficial to the survival of the Black-necked Cranes,which are facing with both cruel natural environments and high predation risks.

Foraging technique and prey-handling time in black-necked stork(Ephippiorhynchus asiaticus)

The foraging technique and prey-handling time of the black-necked stork(Ephippiorhynchus asiaticus)was stud-ied in Dudhwa National Park,India,from January 1996 to June 1997.The habitat in which the storks foraged played an important role in selecting a particular technique to procure food.Black-necked storks mostly foraged using a tactile technique(>90%),but sometimes foraged visually.When the water level was estimated to be less than 60 cm,the storks foraged using tactile techniques.There was no difference in the feeding techniques of male and female storks.Foraging attempt rates varied between the sexes in summer(May)and during late winter(February)in 1997.The search time for prey increased when the water level was high and fish were widely distributed.Decreases in water level resulted in concentration of fish in certain areas and this contributed to high fish-catching rates by black-necked storks.Males had a higher success rate of fish capture than females.However,females captured longer fish than males.Prey-handling time increased in both sexes as fish length increased.Fish 4–6 cm long were most frequently taken by the foraging storks.

Number and nest-site selection of breeding black-necked cranes over the past 40 years in the Longbao Wetland Nature Reserve,Qinghai,China

Black-necked crane(Grus nigricollis,BNC),facing serious threats from human activities and habitat variations,is an endangered species classified as vulnerable under the revised IUCN Red List.In this article,we investigated and analyzed the population and nesting microhabitat of BNCs in the Longbao National Nature Reserve(NNR)from 1978 to 2016,and found the number of BNCs increased from 24 in 1978 to 216 in 2016.This establishment of the Longbao NNR represented the activities of protecting endangered animal species are effective.However,the land cover classification results of Landsat images showed that the marsh wetland,which was the BNC’s primary habitat,decreased during 1978–2016,while artificial buildings increased,which affected the habitat of BNCs.The increase in average temperature over the past 40 years has also had an impact on the number of BNCs.BNCs preferred to nest in marsh wetlands or on islands with open water or star-like distributions through observation.The results of the principal component analysis showed that the nearest distance between nests and habitat type were the primary factors influencing nesting site selection.To protect BNC,we suggest decreasing wetland fragmentation,reducing habitat degradation and providing an undisturbed habitat.