Winter propagation of black swans Cygnus atratus is introduced at Kwangpho on the east coast of the Democratic People's Republic of Korea located in the temperate zone of northeast Asia.
The natural lake Kwangpho was selected as a rearing site to provide the environment which matched most closely to black swan's natural habitats. Comparison of the climate data of Kwangpho with Australia and New Zealand led to the conclusion that it is necessary to increase winter temperature to about 10 °C for artificial rearing.
In order to overcome the low temperature with renewable energy, a passive solar greenhouse with a water pond was introduced, where black swans were reared simultaneously while observing the microclimate such as air temperature, humidity and water temperature in winter. When the pond depth was 0.4 m and 0.8 m, there was no significant difference in indoor temperature, so the depth fixed at 0.4 m to reduce pumping power by more than 50%. During the study, 80 mature black swans wintered safely and 13 pairs of them laid 74 eggs, the artificial hatching rate was 65% and the natural hatching rate was 53%. It was confirmed that the passive solar greenhouse with a pond can raise the winter minimum temperature 8~10°C higher than outside, and in this microclimate it is possible to propagate the black swan and it is believed that the greenhouse has great potential to enable the artificial breeding as well as wintering of black swans, in temperate zone occupying wide area of the earth.
This result was published in "Animal Reproduction Science" (Vol. 250, February 2023, 1-12) under the title of " Winter breeding of black swan Cygnus atratus in a solar greenhouse with a water pond" (https://doi.org/10.1016/j.anireprosci.2023.107199).
