Nesting Ecology of Water Bird Species in Kandy Lake, Kandy, Sri Lanka

Abstract

The breeding site of colonial water birds is called a Heronry or Rookery. Although native habitats of water birds are located near the wetlands, presently they are highly adapted to urban areas for nesting. A heronry consists hundreds of birds belonging to different species. Therefore they have inter-specific and intra-specific competition for available resources. The main aim of the study was documenting the nesting ecology of water birds in the heronry of Kandy Lake, Kandy. Observations were done twice a month using block counting method during the breeding seasons of May to September 2016 and 2017, while standard field guides and NIKON binocular (10×42) were used for the identification of birds. Little egret (Egretta garzetta), Great egret (Ardea alba), Intermediate egret (Ardea intermedia), Pond heron (Ardeola grayii), Night heron (Nycticorax nycticorax) and Cattle egret (Bubulcus ibis) belonging to the family Ardeidae were observed in this heronry. Further, Little cormorant (Microcarbo niger) and Great cormorant (Phalacrocorax carbo) belonging to the family Phalacrocoracoracidae were also observed. However, Little Cormorant was the most abundant nesting species throughout the nesting season. Although Great cormorants and Great egrets preferred upper part of the trees as their nesting sites, the middle layer was occupied by Little cormorants and Little egrets, while Night herons and Pond herons were nested on lower branches. Therefore there is a stratification of nesting to reduce their inter-specific competition for available space for territories. Furthermore, nesting materials and size of nests varied from species to species. Egrets normally used sticks and twigs while cormorant species used greenish twigs with leaves, while Cormorant species often used Acacia leaves (Acacia auriculiformis) for their nest building. Further, nests of Egrets were wider than its depth and cormorant nests were deeper than its width. Although Cattle egret (Bubulcus ibis) was the dominant roosting water bird species in this heronry, no any single nest was observed during the survey.