Nyunaisuzume (Russet Sparrow) or Sanekatasuzume is a mysterious bird appearing in legend of FUJIWARA no Sanekata, a poet in the Heian period.
FUJIWARA no Sanekata was a noted poet and Emperor Ichijo's valet. However, when Fujiwara no Yukinari backbit Sanekata, he disputed with Yukinari in the court and took Yukinari's crown and threw it away. For his blunder, he was relegated from Kyoto to Mutsu Province (Tohoku region). In those days, Mutsu was a desert area of the district. Sanekata was dead in Mutsu, having a grudge against backstabbers for relegating him and a nostalgia for Kyoto.
As soon as the news of Sanekata's death reached Kyoto, a strange rumor started to circulate. Rumor had it that every morning one sparrow entered the Seiryoden Chamber of the Dairi (Imperial Palace) in Kyoto, and it ate up cooked rice on daiban (a table on which food was served) in a split second. People thought that a deep-seated grudge of Sanekata wishing to return Kyoto should have transformed into the sparrow, or the soul of Sanekata had possessed the sparrow. They called the sparrow "Nyunai-suzume" (literally, dairi entering sparrow) or "Sanekata-suzume" (literally, Sanekata sparrow). Moreover, the sparrow allegedly ate and harm crops. People reportedly considered it a deed of the vindictive spirit of Sanekata and was highly afraid.
At that time, there happened also something unusual in Kangakuin, which was a Daigaku-besso (an academic facility for nobles) of the Fujiwara family. A sparrow appeared in a dream to Kanchi Shonin, chief priest of the Kangakuin. The sparrow said that he was Sanekata having transmuted into a sparrow to come back to Kyoto and asked for chanting a sutra for him. The next morning, Shonin found the corpse of a sparrow between the trees in the temple precincts. He was convinced that it should be the remains of Sanekata and built a mound to perform a memorial service for his soul.
Afterwards, the Kangakuin was renamed Kyoshaku-ji Temple (commonly known as Suzume-dera Temple), and the temple is now relocated in Sakyo Ward, Kyoto City. Its property has gradually been diminished due to several fires, and the vestige of the original Kangakuin has been fading. However, the mound that is called Suzumezuka still exists, and the memorial service is still continually held for Sanekata today.
Birds and insects which migrate seasonally and on a regular basis are frequently identified as human souls, and therefore, one theory has it that Russet (or Cinnamon) Sparrows which actually breed in Tohoku region in summer, migrate all over the country and damage agricultural products in autumn would probably be associated with the incarnation of Sanekata who had been relegated to Tohoku.