Use of display platforms of Common Coots (Fulica atra) compared with the use of nests during breeding seasons

We investigated a breeding population of Common Coots (Fulica atra) from April to June in 2008 and 2009. We found that each pair of coots built display platforms beside their nest in their territory during the breeding season. On average, 3.1 (range 2-7) platforms were built by each pair of coots. Display platforms were simpler with less coverage and were significantly lower above the water surface than nests; however, their depth below the water surface was not significantly different. Platforms were primarily used for roosting, preening and mating in the breeding season, but they were also used to store animal food. In the breeding season, nest was usually built later than platforms, the use ratio (total and daily frequency) of platforms decreased after nest was built, and more mating behavior was performed on the nest than on the platform. We compared the use ratio of both sexes to the nest and platforms in different breeding phases; the results show that females used the nest more than the platforms, while males used the platforms more than the females, suggesting that females pay more attention to breeding, while males put more energy in territorial defense. Since coots are territorial during the breeding season, the platforms may play an important role in confirming and recognizing territorial boundaries.