Distribution and number of territorial pairs
The distribution of territorial pairs across the lake could be an insinuation of availability and abundance of food resources, a factor described as probably stable in perennial wetlands (Brown & Britton, 1980), and may also suggest non-variation of lake’s conditions. This study has also shown that other factors are also important in determining pair densities and distribution. The number of pairs observed is also expected from the vastness of the marshes that occur across the entire stretch of the lake. Such a high number might moreover be a suggestion of degradation of alternative breeding habitats and increased disturbances from humans (e.g. poaching, vegetation harvesting, fishing etc.) that coerce cranes (and other birds) to seek and congregate in a few ‘safer’ sites that may result to competition for resources (Goss-Custard, Triplet, Sueur & West, 2006; Watson, Bolton & Monaghan, 2014).
Pairs occupied territories all around the lake except for a 4 km stretch on the south-western shores (Figure 2). This section is characterised by a complete lack of marshes, a steep shoreline and a dense cover of a 1 m tall Pennisetum spacelata tussock grass unsuitable for cranes due to poor visibility and associated high risk of terrestrial predators, such as feral dogs, and poachers. Some sections of the lake such as at Gatumbiro have extensive marshes but a low occupation by cranes. This could perhaps be due the high traffic of fishermen on canoes, and a quarry in the heavily encroached and settled riparian grassland. Kianjata marshes are spread out and stable in terms of vegetation - useful as nest substrates, and provision of cover and shelter from wind. However, these marshes are frequented by a large number of livestock, fishermen, and poachers and were recently subdivided into small (50’x100’) land parcels with upcoming homesteads and barbed wire fences presenting an unfavourable landscape.