[Objectives] The Cattle Egret (Bubulcus ibis) dispersed from Africa to the Americas and became an invasive species raising the attention of ecologists worldwide. However, the dynamics of nest space niche partitioning among Cattle Egret and its competitive species is unclear. In order to understand the dynamics of nest space niche partitioning among Cattle Egret and other mixed-species of breeding heron community, the community composition was investigated together with the nest space pattern in Dali old town, Yunnan, China, during the springs and summers of 2012, 2016 and 2021. [Methods] The study site is located in the forest belt (100°09′36″ E, 25°42′14″ N) along Zhonghe River in Dali old town, Yunnan Province. It is composed of two forest patches, namely old breeding sites (A, the breeding sites used by herons in 2012, but not used by herons in 2016 and 2021) and new breeding sites (B, the breeding sites not used by herons in 2012, respectively) (Fig. 1). The number, location and owner of nests were determined by direct observation. The east – west and north – south distribution of nests was assessed using markers set up during the preliminary survey. The distance between nests and the main trunk were estimated using the arm length and step length of the investigator. The height of nests was estimated using a 5 m fishing pole. The niche widths of each heron species were calculated based on Shannon–Wiener diversity index and the niche overlap index formula of Schoener (1968) was used to calculate the niche overlap between two heron species. [Results] The results showed that in 2012 and 2016, the heronry hosted individuals of Cattle Egret, Little Egret (Egretta garzetta) and Black-crowned Night Heron (Nycticorax nycticorax), with Black-crowned Night Heron being the dominant species (Fig. 2). In 2021, the Intermediate Egret (Ardea intermedia) was added in the community and the Cattle Egret became the dominant species (Fig. 2). From 2016 to 2021, the nest density of Cattle Egret increased significantly, while those of Black-crowned Night Heron and Little Egret decreased (Table 1). By comparing the changes of nest space niche widths of the three species occurring both in 2016 and 2021, it was found that Cattle Egret was more generalized in nest site use, while the Black-crowned Night Heron and Little Egret were more specialized (Table 2). The values of nest niche overlap indicated a more intense competition for nesting sites in 2021 between Cattle Egrets and the other two species, with the one against the Black-crowned herons being more pronounced (Table 3). [Conclusion] Our study showed that, during the period 2012, 2016 and 2021, the Cattle Egrets outcompeted the primary dominant and bigger Black-crowned Night Herons in Dali old town of Yunnan Province, China, restructuring the community composition and nest space niche partitioning of the colonial ardeid.