Some interest was expressed in the Alberta Classic Discussions regarding a page showing images of eyes of young birds as they change with time. Below is our attempt at such a pictorial representation. Clicking on an eye image will give you an enlargement.
Please note the difference in the amount of color above in CU 2003 10262 at 31 days of age and CU 2003 10255 at 30 days of age.
The difference can be due to genetic factors, the increased exposure to sunlight, or a combination of the two. The week prior to the image of CU 2003 10262 at 31 days of age, the bird spent the days in an aviary but not so CU 2003 10255. CU 2003 10255 spent the week prior to the
image of CU 2003 10255 at 30 days of age in a closed loft. Its eyes were therefore not exposed to direct sunlight. It was decided to inquire a little more into the cause of this "color explosion". 2 siblings of
CU 2003 10256 were used. Beginning on day 9 after hatching, CU 2003 10263 spent 8 hours per day in an aviary
whereas CU 2003 10264 spent the day in the nest box
where both of them were born.
Please note the difference in the amount of color in the 2 images at 23 days, although both are of the same age and both are nest mates. They should therefore be genetically similar. Exposure to direct sunlight may appear to accelerate the maturation of the pigeon eye. An alternate interpretation could be that the stress of moving the youngster on a daily basis caused the accelerated maturity of the eye although it seems to have had the opposite effect on general growth. Please note also the almost complete absence of the C/C ("Circle of Correlation") in the light exposed eye. It appears as if the capillaries of the iris move right to the C/A ("circle of adaptation") which is very different in the eye of CU 2003 10264 at 23 days of age. Could this also be an effect due to increased exposure to light?
Questions, just questions ...
Below is another pair of nest mates, treated in an identical fashion as the pair above, except that the light exposure of the top eye begins on the day the first image is taken:
Please note that there is more color in the eye at the bottom at 23 days, the eye which was not exposed to extra light. However, there is more color in the top eye at 32 days. Is the 32 day image the result of the previous light exposure? It is quite possible that light exposure did mature the eye of 10265 faster than it would have done without extra light but its development at 17 days of age was so far behind that of 10266 that the images at 23 days do not tell the complete story. It is surprising how much genetic diversity exists even in nest mates. One can open the enlargements of CU 2003 10265 at 17 days of age and CU 2003 10266 at 17 days of age and compare both windows side by side on a monitor with a resolution setting of at least 1280 X 1024. Please note that one can clearly see the eye of CU 2003 10266 being more mature than the eye of CU 2003 10265 already at 17 days of age.
Please note how accurately the images taken with our artificial light reflect the images taken under sun light. Please note also how much better the images are rendered under artificial light as the reflections are minimized and the colors can be seen to better advantage.
Eyes of very young pigeons have a tendency to show reflections much more easily than the eyes of older pigeons. I liken this to looking through a window when it is dark outside. One does not see much of the outside but sees oneself and the room behind oneself reflected by the sheet of glass in a way similar to how the photographer him- or her-self is reflected by the cornea of the immature pigeon eye. The situation is very different when it is bright outside or when one takes images of the adult pigeon eye.
I therefore decided to make changes to the way I record these eye images. Instead of having to rely on the sun for light, I fixed a fiber optic bundle to the top of the Nikon COOLPIX 4500 camera. The light source to this bundle is an out-dated dental curing light which uses a 150 W Halogen bulb. Please note the absence of the photographer's reflections beginning with the images "CU 2003 10275 at 10 days of age" above which were taken in a dark room to prevent anything from reflecting. Please note also that more detail can be seen by using this method of recording than by using sun light. Compare these images at 18 days with images taken in sun light above. This is analogous to switching off the light inside the room when one looks through the window when it is dark outside. More of the outside will become visible.