Today I went to a mountain, I like birding in mountains and woodlands. In the morning, some Varied TIts gathered around me with alarm call for hawks. So I though that they had mistake the choice of the call. Few seconds after, I found an Eastern Buzzard. I will write about aging follow. Actually they didn't call toward me but the Buzzard. I watched the situation that 1 or 2 individuals found and made alarm for the Buzzard and approximately 4 individual moved to there. It is naturally that Varied TIts didn't have mistakes at the choice of the calls because they had a lot of time to observe me!
One time Buzzard flied and after that it parched near the road. Really strong alarm for me, you can understand from the pic. Aging of this species is not difficult, the color of iris is different between ages. Adult's irises are blackish and young's irises are pale-color. The genus Haliaeetus, Spilornis, Circus, Accipiter, Aquila and so on has the difference in plumage color between ages. We have to consider the body size that too big to replace all feathers, but also young raptors get the benefit from the difference. It mitigate the struggles adult vs young. The cost of the struggles on long life species is high so avoiding struggles is so adaptive.