Survival of water rail Rallus aquaticus (Aves, Rallidae) embryos exposed to experimental flooding

Rails (family Rallidae) are adapted to wetland habitats, nesting in emergent vegetation where flooding is one of the main factors that contributes to nesting failure rates. We conducted an experiment to test the capacity of water rail and Japanese quail embryos to survive flooding. During the experiment, 52 water rail and 60 quail eggs were divided into three groups. One control group was artificially incubated in standard conditions and the other two groups were submerged during artificial incubation for 2 hours and 3 hours, respectively, in the third week of the incubation period in water at 21 degrees C. A total of 88.2% of water rail eggs hatched in the control group, 83.3% in the 2 h flooded group and 29.4% in the 3 h flooded group. For the quail eggs, 75% hatched in the control group, 10% in the 2 h flooded group and 5% in the 3 h flooded group. Water rail embryos were five times more resistant to 2 h flooding conditions, and approximately twice as resistant to a 3 h immersion compared to quail embryos. The elevated survival rate of water rail embryos may be related to their capacity to enter torpor.