- Unpredicatble, drastic changes in water levels of 1 - 3 metres, dictated by irrigation requirements, can render nesting sites and available cover untenable.
- Chicks are easy prey for opportunistic predators such as cats, rats, Grey Heron, Little Egret and Common Kestrel.
- Inadequate breeding sites sometimes chosen by parent birds (basins with insufficient food resources, or with high, vertical sides and lack of floating material, so that flightless chicks are unable to leave the water once in).
The number of broods per basin is listed below, together with the number of chicks per brood, and the number of successfully-reared birds. Figures are given for breeding success in each basin, and for the overall breeding success in all 5 basins, expressed as a percentage.
Basin A had 3 broods of 4(June), 7 (July) and 5 (Sept) chicks.
None of the 16 chicks survived more than a few days.Breeding success = 0%
Basin B had 3 broods of 5 (May), 3 (June) and 2 (July) chicks.
1 chick was successfully reared from the first brood and 2 from the third.
Breeding success = 3/10 = 30%
Basin C had 2 broods of 4 (May) and 1 (July) chicks.
1 chick was successfully reared from the second brood, none from the first.
Breeding success = 1/5 = 20%
Basin D had 2 broods of 4 (May) and 3 (July) chicks.
2 chicks were successfully reared from the first brood, none from the third.
Breeding success = 2/7 = 28.6%
Basin E had 3 broods of 1 (May), 5 (June) and 5 (July) chicks.
1 chick was successfully reared from the first brood and 3 from the third.
Breeding success = 4/11 = 36%
Overall breeding success = 10/49 = 20.4%