Effects Of Habitat Disturbance On Distribution And Abundance Of Papyrus Endemic Birds In Sio Port Swamp, Western Kenya

Abstract

Papyrus swamps are found patchily around the shores of Lake Victoria mainly along river inflows. Elsewhere, this habitat is widely scattered with notable patches at Lake Naivasha and Lake Jipe. Sio Port is one of Lake Victoria’s Cyperus papyrus swamp located at the mouth of River Sio, North of Lake Victoria on the border of Kenya with Uganda. It is an important bird area of Kenya supporting a wide range of birds; however, this swamp lacks formal protection. The swamp and its immediate surrounding have been encroached by forms of disturbances caused by human activities. This study investigated the different forms of habitat disturbance and their effect on the distribution and abundance of papyrus endemic birds. Data on bird counts, habitat quality and forms of disturbance were collected for a period of six months, in October 2013 to March 2014. Total bird counts were established using Timed Species Count (TSC) and playback call technique, done at every fixed point. The points were 50 m apart alternating left and right. At every fixed point count, the researcher waited for 1 minute, calls of the study species were played to elicit response of the secretive papyrus endemic birds; the number of birds of each species seen or heard only within a radius of 25 meters was recorded for the next 9 minutes before moving to the next point count. Habitat quality (height, density and level of maturity) was determined in 1 m2 plots along transverse transects. Opportunistic observations were made to establish forms of disturbance present during vegetation and bird surveys. Papyrus endemic birds were highly distributed in sites with pure papyrus (55.58%) than in sites with mixed vegetation (44.42%). The abundance of three out of the four endemic birds White-winged Swamp-warbler (F (1, 28) =7.376 p = 0.011), Papyrus Gonolek (F (1, 28) = 5.331, p = 0.029), and Northern Brown throated Weaver (F (1, 28) = 5.734, p = 0.024) was significantly different in mixed and pure papyrus sites. However, the abundance of Greater Swamp-warbler (F (1, 28) =2.718, p = 0.110) were not significantly different in mixed and pure papyrus sites in Sio Port swamp in the study period. Forms of habitat disturbance established were vegetation clearing and invasion by terrestrial and aquatic plants. 76.47% of papyrus vegetation were young and regenerating (0-2 m high), 19.65% were immature papyruses (2-4 m) whereas 3.88% were tall mature papyruses (4-6 m high). Abundance of papyrus endemic birds was negatively correlated with density of vegetation in the height range of 0-2 m (r = -0.018, p = 0.941) and 2-4 m (r = -0.054, p = 0.822), the correlation was not significant. Abundance of papyrus endemic birds was positively and significantly correlated with density of vegetation in the height range of 4-6 m (r = 0.465, p = 0.039), the correlation was significant. Regression equation produced by the relationship was y = 2.590x + 0.465, t = 2.227, p = 0.039. Thus, any change in papyrus density resulted to a change in the abundance of papyrus endemic birds. High level of management of papyrus clearing is required for long term conservation of biodiversity.