Abstract
BackgroundUnderstanding 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.MethodsA 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 2016‒2017 and 2017‒2018.ResultsMultiple 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/m2, 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.ConclusionThe 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.
Highlights
Understanding how overwintering birds choose foraging habitats is very important for conservation management
Foraging habitat selection Four components were determined to have a 65.83% cumulative contribution explaining the PCA results, reflecting the main factors influencing the selection of foraging habitats by Black-necked Crane
The selectivity coefficients (Wi) and selectivity indexes (Ei) showed that Black-necked Crane preferred to choose farmland patches as foraging sites, and these patches were located on semi-sunny slopes, with distances to roads ranging from 50‒100 m, distances to a residence within 100‒500 m, and crop remains of greater than 500 g/m2, and the preferred patches were not machine-plowed
Summary
Understanding how overwintering birds choose foraging habitats is very important for conservation management. Foraging habitat selection by birds is defined as a nonrandom choice by avian individuals of certain feeding sites, which is a connotation of understanding complex behavioral and environmental processes, and it is a decision-making process that researchers need to make an attempt to describe how the observed patterns reflect. An understanding of how birds choose foraging sites is very important for the conservation management of winter migratory birds and their overwintering habitats (GossCustard et al 2002; Davis et al 2014; Kaminski and Elmberg 2014). The Black-necked Crane is mainly distributed in the Qinghai-Tibet Plateau and Yunnan-Guizhou Plateau of China. The Black-necked Crane is considered Vulnerable (VU) according to the IUCN Red List and is a nationally protected species in China (Category I)
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