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Great Egret and Grey Heron Dominated Many Inland Heron Colonies in South Korea

Great egret and grey heron standing together in Warsaw, Poland
Research · Ecology

A nationwide analysis of colonial herons and egrets in South Korea found that grey heron (Ardea cinerea) and great egret (Ardea alba) were the predominant large-bodied species and dominated many inland colony assemblages, while medium- and small-bodied species were more concentrated in southern provinces and western coastal lowlands. The peer-reviewed study was published on 17 June 2026 in Scientific Reports.

Researchers compiled species-specific nest counts from 176 active breeding colonies surveyed during the 2018 and 2019 breeding seasons. Grey heron occurred at 166 colonies and great egret at 134. Medium egret (Ardea intermedia) was recorded at 54 colonies, little egret (Egretta garzetta) at 46, black-crowned night heron (Nycticorax nycticorax) at 45 and eastern cattle egret (Ardea coromanda), referred to as cattle egret in the study, at 40.

Regional structure was not uniform. Southern inland and southeastern colonies often formed large mixed aggregations dominated by grey heron and great egret. Colonies in metropolitan areas and western coastal plains more often included little egret, eastern cattle egret and black-crowned night heron, while central inland and east-coast colonies tended to be smaller and simpler, often with only one or two breeding species.

Six colony groups separated large-bodied and smaller-species assemblages

The researchers used a self-organizing map to classify colonies according to their combination and abundance of breeding species. A self-organizing map groups colonies with similar multi-species nest compositions without imposing predefined categories. The analysis produced six distinct colony groups that differed in dominant species, species richness and geographic distribution.

Two groups, III and VI, were strongly dominated by large-bodied species, which accounted for more than 90% of their nests. Group V showed the opposite structure: medium- and small-bodied species contributed more than 80% of nests. The remaining groups had more mixed compositions.

Different landscape variables mattered at different distances

They then compared those colony groups with surrounding land cover at five spatial scales: 500 metres, 1 kilometre, 3 kilometres, 5 kilometres and 10 kilometres. Random Forest models ranked which land-cover variables were most useful for distinguishing the colony groups at each distance. The models had only modest classification accuracy, so the authors treat them primarily as exploratory tools for comparing the relative importance of landscape variables rather than as precise predictors of colony-group identity. The environmental variables associated most strongly with colony identity changed with scale.

Built-up land, managed herbaceous vegetation and water-related cover were important at fine scales. Natural grasslands, bare land and tree-related vegetation became more prominent at intermediate scales, while broader land-use variables remained influential at 10 kilometres.

The authors conclude that the composition of mixed heron and egret colonies reflects landscape conditions operating at several nested spatial scales rather than at the immediate breeding site alone. They present the national analysis as a framework for understanding how future land-use change may reorganize the landscapes supporting colonial wading birds in South Korea.

Sources and image credit

  1. Lee, S., Choi, H.-I., Hwang, J.-W., Lee, J.-Y., Kim, D.-W., Choi, Y.-S., & Nam, H.-K. (2026). Multi-scale environmental drivers of heron and egret colony assemblages in Korea using self-organizing map clustering. Scientific Reports. https://doi.org/10.1038/s41598-026-57885-5Primary peer-reviewed article, published 17 June 2026. Species-specific nest counts from 176 South Korean breeding colonies were classified into six assemblage groups; landscape predictors of colony identity varied across 500 m, 1 km, 3 km, 5 km and 10 km scales.
  2. Nature Portfolio. (2026). Multi-scale environmental drivers of heron and egret colony assemblages in Korea using self-organizing map clustering [Article page].Publisher page confirming the publication date, DOI, study aims and abstract.

Image: Radek Kucharski — wild great egret and grey heron photographed together in Warsaw, Poland, 20 October 2024; Wikimedia Commons/Flickr; representative image of the two large-bodied species that dominated many colonies in the South Korean study · CC BY 2.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Ecology

SPECIES IN THIS STORY

Species in this story

Grey Heron Ardea cinerea Explore species Eastern Cattle Egret Ardea coromanda Explore species Little Egret Egretta garzetta Explore species Great Egret Ardea alba Explore species Black-crowned Night Heron Nycticorax nycticorax Explore species Medium Egret Ardea intermedia Explore species

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