Distribution pattern and densities of breeding pairs
Breeding pairs distribution in the lake mostly occurred in clusters (clumped) in local breeding sites such as Kianjata, Makereka, Kirima and Fuleni (Figure 4). In other parts of the lake, pairs were randomly distributed in a linear manner where the marshes breadth was narrow (100-500 m wide) such as Ziwani/Mairo-Inya and Kanguu.
A total of 123 breeding pairs were mapped during the 2018/2019 breeding season. A hundred and three (103) of the pairs were in the main lake while the rest (20) were in the satellite wetlands, most of which are man-made reservoirs in private land (Figure 4). It is, however, important to note that only 61% and 80% of the mapped breeding pairs attempted breeding (where the pair was observed as at least incubating) in the lake and satellite wetlands respectively. Overall, 64% of the 123 breeding pairs attempted breeding during the season in consideration.
Dividing the lake into 3 sections each c.10 km long, the highest number of breeding pairs were in the middle section (52) followed by the southern section (32) while 19 were in the north. The average density of breeding pairs in the lake’s marshes was 6.50±0.84 (SE) pairs/km2. The highest density was recorded in the middle section breeding sites at 7.14±1.64 pairs/km2closely followed by the southern section at 7.10±1.10 pairs/km2 while the lowest density was in the northern section at 4.76±1.28 pairs/km2.
The mean distance between any two neighbouring breeding pairs was 302.53±17.02 (SE) m, and a minimum and maximum of 47 m and 759 m respectively. A majority (n =20) of the breeding pairs’ positions were in the range of 201-280 m (Figure 5). These distances were however observed to vary in different clusters of nests in the north, middle and south sections of the Lake, and would be expected to vary in different breeding seasons as new pairs take up territories and conditions in the breeding habitat change.