Distribution and abundance of the Shoebill, Balaeniceps Rex in two contrasting wetlands on the shores of Lake Victoria

Abstract

The Shoebill, Balaeniceps rex, a vulnerable bird species on the International Union of Conservation of Nature (IUCN) Red Data List is known to have a declining population all over its range in Africa with about 3300-5300 mature individuals left. Some aspects of its ecology such as behavior, abundance, distribution and threats form key elements in its conservation and yet not well known in much of its geographical range. This study was conducted in Mabamba wetland, an Important Bird Area (IBA) and a Ramsar Site and Makanaga wetland, a non-designated area. The study was conducted from July 2017 to March 2019 to document the; (i) abundance and distribution, (ii) habitat preferences and (iii) threats to the Shoebill. Boat surveys were done once every month for each of the sites and the number of shoebills, dominant plant species in areas where the Shoebill was sighted and the threats were noted. The density of Shoebill sightings was determined. Kruskal-Wallis Test to test for differences in Shoebill sightings across months, Mann-Whitney U Test to test for differences in Shoebill sightings between the two wetlands and regression of threats against the Shoebill abundance were done in R version 4.0.2. The percentage cover of each plant species was calculated in ArcGis Version 10.4.1. A total of one hundred seven (107) Shoebill sightings (58 in Mabamba and 49 in Makanaga wetlands) were recorded during the study period. On average, Mabamba Wetland recorded a higher number of Shoebill sightings per month (1.34±1.93 individuals per square kilometer (km-2) than Makanaga wetland which recorded 0.85±1.64 Shoebill sightings km-2. The highest number of Shoebill sightings were recorded in areas dominated by; Miscanthus violaceus (28), followed by Cyclosorus interruptus (Ferns) (25) and Nymphaea nouchali (water lilies) (18) while the lowest number of sightings were recorded in Pistia stratiotes (1) and Fuirena stricta (1). The general linear model showed that the abundance of shoebills declines with increasing number of fishing boats (Likelihood ratio test; LRT = 5.72, df = 1, p = 0.017). The results suggest that designating an area as an IBA can provide more protection to shoebills as compared to the undesignated area. Shoebills showed a preference for areas of the wetland dominated by M. violaceus, C. interruptus (Ferns) and N. nouchali and therefore such areas ought to be protected.