1 month passed from the end of last year. Today I finished my exam! Daurian Redstart is common winter visitor in Japan and it always perch on the tip of the vertical branch. Daurian Redstart is the most "fall down forager" in Turdidae in Japan. Why they fall down and what the adaptation of it? Today I focus on the tail length. The tail lengths of each species male are following ; Daurian Redstart 62-66mm, Common Redstart 52-68mm, Black Redstart 58-63mm (Above Phoenicurus ), Red-flancked Bluetail 53-62mm(Tarsiger), Common Stonechat 42-55mm(Saxicola). certainly there is a bias because I choose only 5 species, however we can see the differences of tail length in same guild. I think long tail of Redstart helps the foraging that the aspect of momentum, weight and deceleration. From the measurement, we can guess the difference of their Niche! However the problematic consequence is Bluetail. I will write about that someday.
I judged the age of this individual as 1st winter from worn primary covers. And I heard that older adult has dark-tone tip of tail, and I observed many individuals that has dark-tone tip tail. This individual's tail tip is not dark. Really wanna know why the color changed only older adult and why only tip of tail? Is it used as a signal? Spring vacation has started and I had some accidents so now I little worry about it.