Japan's Emperor Naruhito and Empress Masako have observed rare birds at a wildlife conservation center located in the country's largest wetland.

The Imperial couple visited the Kushiro-shitsugen Wildlife Center in the northern prefecture of Hokkaido on Saturday.

The facility is operated by the Environment Ministry and located in a national park centered on the Kushiro Marsh -- Japan's largest wetland registered for international protection under the Ramsar Convention.

Visitors can learn the habits of wild birds designated as endangered species. The Imperial couple viewed a recreation of the habitat of the Blakiston's fish owl, which is native to Hokkaido.

A conservation center official said the Emperor asked how local forests are being preserved.

Rare birds, such as white-tailed sea eagles and Steller's sea eagles, are kept in a cage outside the facility. They are not able to be released back into the wild for various reasons. Some sustained injuries when they were hit by trains or flew into power lines.

The Imperial couple viewed the birds through a small window. They said it is a great effort and that they appreciate the good work.