Herons and egrets


Understanding the mechanisms of habitat selection is fundamental for constructing proper conservation and management plans for avian species. Studying site selection strategies of colonial species is especially complex, as researchers have to deal with collective decision-making for breeding-site selection. Using spatial distribution of the species at landscape level, together with the habitat maps provided by the recently available satellite images, can help us to analyze the collective decision-making strategies. 

I used distribution of the colonies of herons and egrets in the Kanto Plain, Japan,  combined with landscape data to study colony site selection strategies, and their variations across landscapes and over the years.

We found that herons and egrets select their colony sites based on habitat preferences that depended on scale. One of the most exciting results was finding that these scales can be affected by landscape complexity. Site fidelity affects also colony site selection, and its influence varies over time. Long-term analysis of colony site selection is fundamental as there exists high inter-annual variability in colony site selection. 

We recently started to compare our findings in Japan with the colony site selection patterns of herons and egrets in North Italy in a collaboration with the University of Pavia. We observed how site fidelity was even higher in this region and how the site fidelity levels changed over the years.