The hototogisu is a kind of Japanese cuckoo (Cuculus poliocephalus). The song of the hototogisu traditionally signaled the arrival of summer. In other tales, the mournful cry of a hototogisu in a lonely wood was associated with the longing of the spirits of the dead to return to their loved ones still living. The hototogisu has long been a popular subject in Japanese literature and poetry, making appearances in both The Tale of Genji and The Pillow Book, and practically comprising an entire genre of hototogisu haiku.
The hototogisu is also the is also the subject of a famous set of sayings used to compare the personalities of Japan's three great unifiers - Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu:
Nobunaga: Nakanakuba koroshite shimaou hototogisu ("If the hotogisu doesn't sing, kill it.")
Hideyoshi: Nakanakuba nakasete miseyou hototogisu ("If the hototogisu doesn't sing, force it to.")
Ieyasu: Nakanakuba nakumade matou hototogisu ("If the hototogisu doesn't sing, wait.")
There are no less than nine ways to write "hototogisu" using Japanese kanji, only some of which have meanings that actually reflect the bird they name:
杜鵑, "woods cuckoo"
子規, "egg measuring" (may suggest the bird's practice of laying eggs in the nest of other birds)
時鳥, "bird of time"
蜀魂, "spirit of Szechuan"
霍公鳥, "speedy cuckoo bird"
田鵑, "rice field cuckoo"
沓手鳥, "shoe hand bird"
杜宇, "woods' roof"
Suffice to say, "hototogisu" is usually written in hiragana.