A research project into the Ketupa flavipes, commonly known as the tawny fish owl, recently made some discoveries on the lives and reproductive habits of the nation’s largest and most mysterious owl.
After the remains of a Oncorhynchus masou formosanus, commonly known as the Formosan landlocked salmon or the Taiwanese salmon, were discovered in a remote area several years ago, officials at the Shei-Pa National Park Headquarters said they suspected they were left there by fish owls.
Because the tawny fish owl is the only member of the genus Ketupa genus in Taiwan, there are few left and it is nocturnal, little is known about it. Therefore, the national park headquarters asked Institute of Wildlife Conservation head Sun Yuan-hsun (孫元勳) at the National Pingtung University of Science and Technology to conduct research into the habits of the tawny fish owl.
Some academics say the fish owls should not be considered a single Ketupa genus, but belong under the genus Bubo, which includes most Ketupa species.
To find out more about the owl’s habits, researchers tagged captured tawny fish owls with radio receivers before releasing them into the wild.
It was discovered that the owls had not killed the salmon because the fish lived too deep under water for the owls to hunt them.
Formosan landlocked salmon ecology center deputy director Yang Cheng-shiung (楊正雄) said the research showed that the owl’s main sources of food were toads, rodents and Onychostoma barbatulum, also known as the Taiwanese shovel-jaw carp.
Research also shed light on the birds’ mating habits.
Yang said tawny fish owls were quite romantic. They interchange a wide range of high and low-pitch melodies in their songs to attract a mate.
While the male owls provide for the females during mating, they do not part after mating, and often live in the same nest long after their owlets have hatched and flown away.
While many birds mate only once a season, or even engage in “one-night stands,” like the mating habit of the greater painted stripe, tawny fish owls seem to mate for life, and only accept another owl into their lives if their partner has passed away.
During the period of research, none of the researchers found any evidence that tawny fish owls cheat on their mates.
Near a spot where the Cijiawan River (七家灣溪) converges with another body of water, the researchers found two owl couples nesting near each other.
While the owls did not cheat on their mates, they were very territorial, constantly warning their neighbors not to cross into their territory, Sun said, adding that sometimes such “disputes” lasted all night long.
One specimen the researcher studied was a female tawny fish owl named “Sheng Jie” (勝姊). The owl had no nest and wandered around the woods. After being accepted as the new mate of a male owl that had lost its mate three years earlier, Sheng Jie settled down with the male and tended the area he had made his home, Yang said.
After the male died the next year, Sheng Jie partnered with another male and continued to live in the nest of her deceased partner, Yang said, adding that in her three years of research, Sheng Jie gave birth twice, rearing a total of three owlets, one presumably with her previous partner.
According to the researchers, the owlets continued to return to the nest after they were old enough to leave it. However, because owls are nocturnal, humans rarely see mother owls and their owlets flying together.