Abstract
Reed beds represent an important habitat for the survival of birds by providing favorable foraging and reproduction conditions. Reed management, as a traditional agricultural activity, primarily includes water level control and vegetation removal by cutting. Red-crowned crane (Grus japonensis) is one of the most endangered cranes, and their population continues to decline due to habitat loss caused by artificial activities. A lack of research relating to how reed management affects crane habitat distribution patterns throughout the wintering period hinders our ability to offer conservation recommendations. In the present study, we explored the effect of reed management on the habitat distribution patterns and analyzed the food resources of red-crowned crane in the Yancheng National Nature Reserve (YNNR). According to the reed management activities in December, we divided the wintering period into two phases: the preharvest period and the postharvest period. Throughout the wintering period, the number of cranes recorded in the common seepweed (Suaeda glauca) tidal flats remained stable, but cranes were rarely recorded in the smooth cordgrass (Spartina alterniflora) tidal flats and aquaculture fish ponds. The number of cranes, however, showed a noticeable fluctuation in the reed beds during the two periods. Before the reed harvest, only a small proportion of cranes were recorded in the reed beds (relative abundance = 2.9%). However, more cranes (relative abundance = 61.0%) were recorded after the reed harvest. Water was introduced from adjacent rivers and fish ponds to submerge the cut reed beds. Changes in potential animal food resources (items and biomass) might be one of the vital reasons for the preference of cranes to the postharvest reed beds. Our results suggest that traditional reed management in the YNNR could benefit this flagship crane species that winters in the wetland system. However, as reed harvest has been forbidden in the core zone for conservation purposes since 2016, further research is needed to verify whether forbidding the harvest of reeds is reasonable.
Highlights
Common reed (Phragmites australis (Cav.) Trin. ex Steud.) is a tall grass species that is widely distributed in wetlands and is of economic and ecological importance
A total of 1,586 individual cranes in the four types of habitat, including smooth cordgrass tidal flats, common seepweed tidal flats, reed beds and aquaculture fish ponds, in the core zone of the Yancheng National Nature Reserve (YNNR) were recorded during our study period
Throughout the wintering period, the number of cranes recorded in the common seepweed tidal flats remained stable (R2 = 0.031, F = 3.244, df = 69, and P = 0.076, linear regression), whereas the number increased significantly (R2 = 0.625, F = 111.7, df = 69, and P = 0.000) in the reed beds throughout the wintering period (Fig. 3)
Summary
Common reed (Phragmites australis (Cav.) Trin. ex Steud.) is a tall grass species that is widely distributed in wetlands and is of economic and ecological importance. Wetlands dominated by the common reed, known as reed beds, occur in both natural conditions and artificial settings that host an array of species of conservation importance (Schmidt et al, 2005; Mer’o et al, 2018). The abundance of passerines decreases in managed reed beds (Mer’o, Lontay & Lengyel, 2015). An important factor that might negatively affect the abundance of passerines in managed sites is food limitation. Important prey groups for passerines, including butterflies (Lepidoptera), beetles (Coleoptera) and some spiders (Araneae), have been reduced in managed sites (Valkama, Lyytinen & Koricheva, 2008). Managed reed beds are relatively less suitable habitats for passerine species due to the lack of available food resources
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