Effects of spatial and temporal crop changes on bird diversity in peri‑urban agricultural lands

Numerous studies have investigated bird diversity-environment relationships in agricultural landscapes. While many studies have emphasized the importance of natural/semi-natural elements and their diversity within or surrounding farmlands, it remains unclear how crop diversity impacts birds. There is also a significant gap in our knowledge regarding the effects of temporal changes in crop composition on bird diversity. Using small farmlands in a sub-tropical city of China, we examined how spatial and temporal variation of crops and other local farmland features was linked to species diversity of birds and their traits. In small peri‑urban agricultural areas of Guangzhou, we collected bird and crop/non-crop data approximately bimonthly from December 2021 to October 2022. Overall crop diversity and seasonal crop changes were indexed by alpha diversity (Shannon-Wiener index) and beta diversity, respectively. Both alpha and beta crop diversities were positively associated with Shannon-Wiener diversity of birds. Alpha crop diversity also tended to have a positive impact on species richness. Percent cover of woody vegetation showed a positive effect on all three bird diversity indices, i.e., species richness, Shannon-Wiener diversity, and evenness. Percent cover of rice affected species richness positively and evenness negatively, whereas the effects of percent cover of corn were the opposite. In a fourth-corner analysis, the abundance of plant/seed-eating birds was negatively associated with alpha crop diversity, whereas the abundance of ground-foraging birds was positively associated with beta crop diversity. These patterns indicate that seasonally dynamic crop changes as well as local crop diversity can influence bird diversity and traits in small farmlands. They also suggest that natural/semi-natural woody vegetation, such as trees and shrubs, play a critical role in enhancing species diversity of birds in farmlands dominated by herbaceous edible crops.