The Coloration of Eggs
The Coloration of Eggs
Several inquiries have appeared lately in the various ornithological journals as to the time and manner in which the pigments are deposited upon the egg-shell. What is perhaps the most thorough treatise upon this subject will be found in Chapter XII of “A History of Birds”, by W. P. Pycraft. The text is much too long to be quoted here in its entirety, but perhaps the following extract may be of value to those who have not access to the above-named volume. Mr. Pycraft says:
“We may assume that...this pigment is deposited by the walls of the oviduct, and it would seem that in many cases this deposition takes place in two different re gions of the duct, first on the formation of the earlier layers of the shell, where little more than a slight-staining is effected, and later when the shell is nearly complete; in most cases there is no coloration until the egg has nassed some wav down the oviduct. It would then appear that the ground colour first deposited, and after this the peculiar markings of the particular egg. When these are formed while the egg is at rest a sharply defined spot is the result; but it commonly happens that the deposit of pigment takes place while the egg is in motion, smears and blotches being the result; and it would further appear that the egg in its passage rotates, inasmuch as these streaks and lines show a decided spiral arrangement. These various evidences of the process of coloration can be well seen in eggs of many birds of prey, as well as those of...the Guillemots, for example.“
D. I. Shepardson
Los Angeles, California
