Study how do birds reorganize fruits maturation.

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Birds start to bite the fruit when glucose contain was maxed and surface of fruit was getting soft. Some birds make an injury on the surface of fruit to make a softy. It was suggested that induce bird fruit bite was not only color and glucose content of fruit. We have investigated also possibility of smell sense of birds. The ratio of olfactory bulb to whole brain in crow and bulbul was very small. Both sides of olfactory bulb in the crow and bulbul were fused although those of many animals were independent. Therefore, the smell sense of birds may not be developed. Furthermore, avian vision properties were investigated. The population of ganglion cell of crow retina is more than 3,000,000 and there two high populations were in the retina. Density of ganglion cell was going low at the peripheral area of the retina. Oil droplets of the photoreceptor cell were found 5 types such as red, yellow, blue, green and transparent. Those were locating same proportion in the retina. Oil droplets of starling were found also five types and green or yellow-green types were predominant. t crow had high sensitivity in short wavelength. There were four types of opsin in crow's retina and one of them had high sensitivity in UV. Therefore, UV wavelength may be important for crow's vision and it suggested that bird have very high sensitive of color. We compared the characters of fruits chosen by birds. As a result, they may refer some light wavelength reflected from the surface of fruit without sugar content and hardness.