Abstract:
Increasing popularity of bird watching and unplanned tourism activities in ecologically important
wetland habitats in Sri Lanka can potentially cause detrimental impacts on wetland birds. Yet
scientific evidences to assess the extent of these impacts are limited in literature in the tropics.
This study investigated the impacts of recreational disturbances on the behavior of six selected
water-bird species along highly visited nature trails in an internationally important Bundala
Ramsar wetland, Sri Lanka, from July to December 2017. Bird behaviors were observed in five
wetland locations where water-birds are known to occupy regularly. Bird behaviors were
observed and ethograms were prepared using Ad-libitum sampling. Detailed behavioral
information was gathered using focal sampling and scan sampling techniques. For the purpose of
this study, only the disturbance caused by moving vehicles were considered, and the intensity of
disturbance was defined in terms of the speed of passing vehicles. Accordingly, four intensities
of disturbance were considered, i.e. vehicles moving at 10, 20, 30 and 40 km/h speeds. The
behavioral changes when subjected to disturbance was statistically compared. Of the studied
species, the foraging behavior of Painted Stork (Mycteria leucocephala) and Lesser Whistling-
Duck (Dendrocygna javanica) was negatively affected by recreational disturbances. Overall, the
studied birds showed significant negative correlations between the response and the distance to
the source of the disturbance except the Eurasian Spoonbill (Platalea leucorodia). The highest
sensitivity to moving vehicles was shown by the Kentish Plover (Charadrius alexandrinus
seebohmi) (rs=-0.882, p=0.001), followed by the Caspian Tern (Hydroprogne caspia) (rs=-0.834,
p=0.001) i.e. birds are more disturbed as the distance to the source of disturbance decreases.
Spearman's correlations suggest that the Painted Stork is more sensitive to fast moving vehicles.
Eurasian Spoonbill showed no consistent behavioral responses for disturbances indicating
possible habituation. The Asian Openbill (Anastomus oscitans) showed a consistent pattern of
flushing or avoidance behavior for passing vehicles close by irrespective of the speed. The study
findings call for sound visitor management strategies in highly visited coastal wetlands to
minimise the disturbances to water birds. Maintaining a minimum distance to areas of the
wetland that are highly utilised by water birds for foraging, resting and breeding, and strictly
imposing speed limits for vehicles inside the wetlands may be particularly useful in minimising
the disturbances to coastal water birds.
