Declining water depth delayed the breeding time of Fulica atra, not human disturbance

Disturbances by tourists have been considered to delay the breeding time of coots. In this study, we investigated the common coot (Fulica atra) from April to June in 2008, 2009 and 2012 around the Anbanghe Nature Reserve and Daqing Longfeng wetland of Heilongjiang Province. We evaluated the correlations of four habitat factors (water depth under coots' nests, distance of nests to banks, distance of nests to human disturbance and nest coverage) to discuss the impacts of those factors on the breeding time of the coots. The water depth under the nest was significantly correlated with the coots' breeding stages in the Anbanghe wetland. In addition, we investigated the breeding dates of 56 pairs of coots and found the dates were significantly negatively correlated with the water levels under the nest for both of the wetlands. However, the breeding time (breeding stages and dates) of coots was not significantly related to the distance of the nest to disturbance, distance to the bank of the lake or the nest coverage. The LME models and GAMs that related breeding time to water level received the greatest support. For the GAM, in the group with a clear breeding date, water level was the most influential variable; in the group for which only breeding stages could be recognized, nest coverage combined with water level had a lower AICc value than water depth itself. In conclusion, we found no clear evidence to indicate that disturbances from tourism delayed the breeding time of the coots; however, the water level had a clear influence on the breeding time. We inferred that reproduction was delayed in order to wait for the improvement of habitat conditions (such as food resource and concealment). Neither water level nor disturbance impacted the reproductive output of the coots as these variables showed no clear relationships with the clutch size.