Dietary assessment of Little Egrets (Egretta garzetta) by analyzing regurgitated materials during their breeding seasons in Sri Lanka

Abstract

During the breeding seasons the Little Egrets’ feeding grounds become limited to the vicinity of the heronries. Therefore the food availability and their diversity of these areas are important for the survival of offspring. The study was conducted during the breeding seasons from May to September in 2014 and 2015 at five heronries representing different climatic zones in the country (Wet, intermediate and dry) in three districts, Gampaha, Kandy and Anuradhapura in Sri Lanka. Ten fledglings of Little Egrets were randomly caught representing each breeding heronries (n=50) and the regurgitated materials were collected and identified to species level by using standard field guides. A total of 25 faunal species belonging to 5 classes were recorded. Of them, 18 species in year 2014 and 7 new species in 2015 were recorded. Class Pisces had the highest number of species both in year 2014 (13 Nos) & 2015 (11 Nos). These data revealed that the most diversified diet was identified from egrets in Kandy Lake heronry by the values of overall Shannon-Weiner Diversity and Margalef’s Indexes for year 2014 and 2015, while birds in Jaffna Junction heronry were recorded as who owned the lowest diversified diet. Presence of diversified habitat types such as tank ecosystem, canals, marshy areas and paddy fields within the foraging area of Little Egrets in Kandy Lake may be the reason for highest diversity. Also two small brooks with unique micro habitats like runs, riffles and pools support the species diversity of aquatic and semi aquatic fauna. Class Pisces is the most species-rich class of faunal species in regurgitated materials of all sites, however Amphibians, Insects, Crustaceans and reptilians also present in the diet of Little Egrets.