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Four Weeks Old- 6/14/03
Once again we have lined up the chicks left to right: oldest to youngest. The young birds are now beginning to outgrow our ruler. The smallest is about 11 1/2 inches long and the oldest an inch to an inch and a half larger. Their orange iris will turn to bright yellow when they are mature. This change is believed to be linked to hormonal changes.
In the closeup we get a unique look at what is referred to as the nictitating membrane. This is a clear covering, in addition to the upper and lower lids, which moves across the eye for moisture, cleansing, and protection in times of struggle. It can be closed over the eye without interfering with vision.
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