Linking landscape structure and resource availability to coastal bird responses under Spartina alterniflora invasion

The invasion of Spartina alterniflora has profoundly altered habitat composition, landscape patterns, and resource availability in coastal wetlands. However, the large-scale mechanisms through which these changes affect birds with different habitat requirements remain poorly understood. By integrating bird observation data, habitat remote sensing layers, and ecological datasets along the coastal zone of mainland China, this study systematically evaluated how habitat conversion, landscape structure, and resource supply influence mudflat-dependent, vegetation-dependent, and generalist birds under the context of S. alterniflora invasion. Our results demonstrate that S. alterniflora invasion reduces the capacity of coastal wetlands to support bird communities, particularly mudflat-dependent waterbirds. This decline is primarily associated with the loss of open mudflat habitats, which provide essential foraging areas for waterbirds by maintaining unobstructed access to benthic prey resources. Specifically, the conversion of unvegetated mudflats into S. alterniflora saltmarshes substantially weakened habitat support for mudflat-dependent and generalist birds, as dense vegetation altered habitat accessibility and reduced the availability of key foraging spaces. In addition, S. alterniflora invasion modified the landscape configuration of native habitats, influencing bird communities by altering the relationships between landscape structure and resource availability. Our findings highlight that the ecological consequences of S. alterniflora invasion extend beyond habitat area loss, as changes in habitat configuration and resource accessibility can further reduce the functional capacity of coastal wetlands to support bird biodiversity. Consequently, coastal conservation must transition from area-centric restoration toward spatial configuration optimization and quality enhancement to preserve the functional capacity of wetlands in supporting bird biodiversity.