23 March, 2000
Israel Fried
Physical explanations to the "eye" in the train of the blue peacock (Pavo cristatus L)
Abstract
I suggest physical explanation to the "eye" in the train of the blue peacock, i.e. the male of the
Indian Peafowl (Pavo cristatus L). Generally, a bird's tail is used for stabilizing weight balance and aerodynamic forces
when flying and when perching on a branch. The genus of the birds Pavo pheasants are those with the "eye" like pattern on
the edge of their long tail (train). The source of those pheasants is in the jungles of SouthEast Asia where there are strong
winds due to the monsoons all over the year. The blue peacock was used to roost and foraging for food at the top of the taller
trees, probably in order to bring high quality food to the females and young waiting on the ground or on the low branches.
The long train belongs to the males only.
I show that the "eye" might function as an automatic controller against strong winds. I suggest that
the control mechanism be by enabling a separation of the barbules in those "eyes" by the right amount under all kinds of winds.
This include turbulent winds coming from many directions in a variety of strengths, while the winds may be changed abruptly
locally on each separate feather, as might be the case at the top of the tall trees in the monsoons jungles. I recall works
of others, which show that the colors in the "eye" are due to interference from melanin lattices with specific spacing between
the layers. I suggest a connection between the quantity and density of the melanin layers and the mechanical properties of
the barbules, which allow the opening of the barbules in each colored zone under specific levels of wind intensity.
