Abbas Ashoori; Seyed Farshid Fallah; Farhad Hosseini Tayefeh
Abstract
This study aimed to describe the breeding biology of the Great Crested Grebe during the breeding season from April to September 2015 in the western part of Anzali wetland. A total of 56 nests were identified during this survey. Totals of 18 and 20 Great Crested Grebe nests were built simultaneously in ...
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This study aimed to describe the breeding biology of the Great Crested Grebe during the breeding season from April to September 2015 in the western part of Anzali wetland. A total of 56 nests were identified during this survey. Totals of 18 and 20 Great Crested Grebe nests were built simultaneously in two separate colonies from mid-April to early May, and in addition at least two months later, a further 18 nests with a minimum distance of 100 meters from each other within Whiskered Tern colonies. The mean clutch size was 3.91±0.85 (n= 56), the average weight of the eggs was 38.8±3.01 g (n= 68) and the average volume of eggs was 37.00±3.6 cm3 (n= 68). This study showed that Great Crested Grebes have a long breeding period in the western part of Anzali wetland (more than 170 days). Breeding success is affected by the large area of the water body which has large waves in spring, as well as the presence of predators such as Marsh Harrier. The first nests in the colony are constructed in the margins of the wetland and among small clumps of reeds. Subsequently, with the gradual increase in the growth and biomass of submerged water plants in the water body and the start of Whiskered Tern nesting on these water plants, the grebes build individual nests among the large colonies of Whiskered Terns. This may represent a specific breeding strategy of the Great Crested Grebe to increase the number of chicks reared during the breeding season.
