Breeding biology of Great White Pelican Pelecanus onocrotalus at Lake Tana, Ethiopia

Abstract

Great White Pelicans, once thriving at Lake Shala, have faced a decline in breeding pairs at Lake Abijata due to increased salinity and overfishing. A study at Lake Tana Biosphere, from December 2020 to December 2021, aimed to understand their breeding biology, which had not been previously documented. We conducted intensive searches for nests and monitored them during incubation and post-hatching to assess reproductive success. The study found pelicans breed year-round, with peaks from late December to March and June to July. The average clutch size was 2.14, with egg dimensions averaging 90.33 mm in length and 58.70 mm in breadth and a mean weight of 173.68 g. No significant differences were observed in these measurements, but a positive correlation was found between egg length, weight, and breadth and weight. However, no correlation existed between length and breadth. Out of 98 eggs, 84 hatched, resulting in 80 and 91.5 % hatchability rates across two breeding seasons, averaging 85.71 %. The hatching success rate did not differ significantly between seasons. Unfortunately, only 37 pelicans reached the pre-fledging stage, indicating a high mortality rate of 63 %. The study concluded that the breeding performance of Great White Pelicans at Lake Tana is poor, with human disturbance, overfishing, and predation on nestlings posing significant threats to their nesting success. This highlights the need for conservation efforts to address these challenges and protect the species.