Population size and factors affecting the distribution of Pelecanus philippensis (Pelecaniformes: Pelicanidae) in Colombo district, the Western province of Sri Lanka

Abstract

Spot-billed Pelican (Pelecanus philippensis) is a near-threatened bird found only in South and Southeast Asia. Colombo, the commercial capital of Sri Lanka, holds a naturalized population of P. philippensis released from captive collections of the National Zoological Gardens, Dehiwala. This study was conducted to investigate the distribution of P. philippensis and assess its population size in the Colombo district. We measured environmental variables and counted the number of birds foraging in all the water bodies with surface area >0.05Km2. The rest of the water bodies were also observed to record the presence of pelicans. A roosting count of pelicans was conducted from April to December 2020 to assess their population size. P. philippensis was distributed in 14 lentic water bodies within the Colombo district and its minimum estimated population size was 193 individuals. Land-use patterns around the water body did not significantly impact (P>0.05) the distribution of pelicans. They were not recorded in water bodies with more than 10% vegetation cover. The abundance of P. philippensis in foraging sites was positively related to the chlorophyll-a content of the water (P<0.05). As it is the flagship faunal species in Colombo, its conservation needs immediate action from relevant authorities.Conclusion Taken together, the distribution of Zn2+ ions in different aquatic species is species-specific. Furthermore, the present study provides insight into the potential use of high-affinity low-molecular-weight Zn2+-ion-selective fluorescence probes to detect labile Zn2+ in aquatic organisms and the toxicological implications of zinc pollution in aquatic environments.