During the period of incubation, the ostrich, if an intruder approaches its nest, resorts to various artifices to induce him to withdraw far off.
"One morning," says Professor Thunberg, "as I rode past a place where a hen-ostrich sat on her nest, the bird sprang up and pursued me, with a view to prevent my noticing her young ones or her eggs. Every time I turned my horse toward her she retreated ten or twelve paces, but as soon as I rode on she pursued me again."
The period of incubation seems to vary; but, on the average, it may be about thirty-eight days. One or more of the females are said to lay meanwhile; but the supernumerary eggs are placed outside the nest, and are supposed to serve as nourishment for the callow brood. If such really be the case, we in this again see a wonderful provision of nature, inasmuch as the chicken would be unable to digest the indurated matter furnished by their too-often sterile haunts.
The notion so generally entertained of the ostrich merely depositing her eggs in the sand, and leaving them to be vivified by the sun, arises probably from its habit of occasionally quitting the nest in search of food, more especially as it generally does so during the hottest part of the day.
Some travelers affirm that the ostrich not only never sits on her eggs after having once been handled, or even if a man should have passed near the nest, but that she actually destroys them! I, for my part, can not speak to this point, having, whenever I found an ostrich's nest, usually plundered it at once, thus leaving the bird no opportunity of obeying so strange an instinct.
It seems pretty certain, however, that the ostrich, as with many other birds, is in the habit of deserting her eggs if they be handled. "The slaves," says Professor Thunberg, "always use the precaution not to take away the eggs with their hands (in which case the birds, who perceive it by scent, are