Influence of breeding time, nest size, and egg size on the breeding success of the Common Moorhen Gallinula chloropus

We investigated the relationships between the breeding success of the Common Moorhen Gallinula chloropus and its breeding time, nest size, and egg size in a man-made wetland (Ab-bandan) during the 2008 breeding season in Mazandaran Province, northern Iran. For each nest, the date of the first laid egg, the first hatching, and the first fledgling was recorded as well as the clutch size. Nest characteristics (height, depth, diameter, and water level underneath) and egg characteristics (shape index and weight) were measured. The first egg was laid on June 15 and the last chick left the nest on August 30. From 251 eggs in 27 nests, 229 eggs hatched (91.2%) and 204 chicks left the nest (Mean breeding success = 81.3%). A GLM revealed that egg weight negatively affected breeding success (P = 0.024) meaning heavier eggs were less likely to produce fledglings. The specific underlying physiological mechanisms require further investigation.

Automated summary

The study found a negative correlation between the breeding success of the Common Moorhen and egg weight, indicating that heavier eggs were less likely to produce fledglings. In the man-made wetland, approximately 81.3% of the Common Moorhen chicks successfully left the nest.