Diurnal Activity Budget and Habitat Usage of Four Ciconiiformes Species at the Annaiwilundawa Ramsar Wetland Sanctuary, Sri Lanka

Abstract

Annaiwilundawa Ramsar wetland provides suitable habitats for a large number of residentand migratory bird species. Ciconiiformes of the Annaiwilundawa Ramsar wetland forms adiscernible component and hence have been identified as a potential bio-indicator group.Present study recorded the diurnal activity budgets of four Ciconiiformes species, namelyPurple Heron (Ardea purpurea), Intermediate Egret (Ardeola grayii), Indian Pond Heron(Egretta garzetta) and Little Egret (Mesophoyx intermedia) at the Annaiwilundawa Ramsarwetland once a month from December 2011 to November 2012.

The day was divided in to three time periods as morning (6.15-10.15 hrs), noon (10.15-2.15hrs) and evening (2.15-6.15 hrs). Activities of the birds were categorized as feeding,locomotion, resting, preening, alert and searching. The activity of the birds and the habitat inwhich the activity occurred was recorded using focal and scan sampling methods in each timeperiod. Each bird species was observed for 30 minutes in each time period and the location ofthe observed bird species was recorded on a 1:50,000 scale topographical map of theAnnaiwilundawa. The marked points were jointed to conclude the ‘Used Area’ of the relevantspecies.

All four species had significant difference in the diurnal activity budgets in each time period.Resting was the most dominant behaviour of these four species {[PurpleHeron=57.83±18.54%], [Indian Pond Heron=35.42±2.63%], [Little Egret=34.11±3.16%] and[Intermediate Egret=40.12±12.56%]}. Size of the area used by the four Ciconiiformes speciesdid not differ significantly (ANOVA, F=2.064, P≥0.1110). However, they showed significantrelationships between percentage time spent in different habitats and there availability withinthe ‘Used Area’ (Spearman correlation, Purple Heron z = 3.258, P≤0.0011; Indian PondHeron z=3.087, P≤ 0.0020; Little Egret z=1.978, P≤0.0480; Intermediate Egret z=3.335,P≤0.0008). Present study indicated that these four species of Ciconiiformes used theAnnaiwilundawa reservoir primarily for resting. Clear habitat partition and area usage wasobserved which may have allowed these four species to co-exist sympatrically at theAnnaiwilundawa Ramsar wetland.