Nestedness theory suggests wetland fragments with large areas and macrophyte diversity benefit waterbirds

Many artificial wetland constructions are currently underway worldwide to
compensate for the degradation of natural wetland systems. Researchers
face the responsibility of proposing wetland management and species
protection strategies to ensure that constructed wetlands positively
impact waterbird diversity. Nestedness is a commonly occurring pattern for
biotas in fragmented habitats with important implications for
conservation; however, only a few studies have focused on seasonal
waterbird communities in current artificial wetlands. In this study, we
used the nestedness theory for analyzing the annual and seasonal community
structures of waterbirds in artificial wetlands at Lake Dianchi (China) to
suggest artificial wetland management and waterbird conservation
strategies. We carried out three waterbird surveys per month for one year
to observe the annual, spring, summer, autumn, and winter waterbird
assemblages in 27 lakeside artificial wetland fragments. We used the NeD
program to quantify nestedness patterns of waterbirds at the annual and
seasonal levels. We also determined Spearman partial correlations to
examine the associations of nestedness rank and habitat variables to
explore the factors underlying nestedness patterns. We found that annual
and all four seasonal waterbird compositions were nested, and selective
extinction and habitat nestedness were the main factors governing
nestedness. Further, selective colonization was the key driver of
nestedness in autumn and winter waterbirds. We suggest that the area of
wetland fragments should be as large as possible and that habitat
heterogeneity should be maximized to fulfill the conservation needs of
different seasonal waterbirds. Furthermore, we suggest that future studies
should focus on the least area criterion, and that vegetation management
of artificial wetland construction should be based on the notion of
sustainable development for humans and wildlife.