Relationship between bird population sizes with heavy metal concentrations in water from Poyang Lake
 

The correlation analysis between the abundance of various bird species in Poyang Lake and the concentrations of six heavy metals (Cu, Pb, Zn, Ni, Cr, and Cd) in surface water revealed species-specific patterns, with significant relationships (p < 0.05) varying in both direction and magnitude (Figure 1). Several species, including gadwall, northern pintail, Eurasian wigeon and white-napped crane, exhibited significant positive correlations with Cu and Zn, suggesting a possible tolerance or adaptive foraging strategy in environments with elevated but sub-toxic levels of these metals.[9]

 

In contrast, species such as gadwall, Siberian crane and white-napped crane showed marked negative correlations with Ni and Cd, indicating potential sensitivity to contamination and possible avoidance of polluted habitats.[2] The predominance of positive associations among more pollution-tolerant and resident species aligns with previous findings that certain waterbirds can persist in, and even exploit, habitats with moderate metal enrichment due to dietary plasticity and detoxification mechanisms.[10] Comparable trends have been reported in studies where waterbirds’ feathers, acting as bioindicators, reflected both bioaccumulation from aquatic food webs and differences in ecological niche, with tolerant species often displaying higher feather Cu and Pb concentrations without apparent population decline.[1, 7]

 

Overall, these findings emphasize that heavy metal contamination in wetland waters can exert divergent ecological effects, shaping avian community composition by selectively disadvantaging sensitive taxa while allowing tolerant populations to remain stable or even increase in abundance

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​​​Taking Pb as an example to further elucidate the role of heavy metals in shaping avian population dynamics in Poyang Lake, simple linear regressions were performed between waterborne Pb concentrations and the abundances of three representative species—bean goose, gadwall, and white-napped crane (Figure 2).

 

The results revealed a significant positive relationship for bean goose (p < 0.05), indicating that populations of this species increased with rising Pb levels, potentially reflecting dietary habits or habitat use strategies that enable persistence in moderately contaminated environments.[11] In contrast, gadwall and white-napped crane exhibited significant negative relationships (both p < 0.05), suggesting that higher Pb concentrations were associated with reduced abundance, likely due to lower tolerance thresholds or avoidance of polluted feeding grounds.[12]

 

These divergent responses mirror patterns reported in other wetland systems, where heavy metal gradients have been shown to differentially influence waterbird species depending on their foraging guilds, migration strategies, and physiological detoxification capacities.[13, 14]