INCUBATION. 253 



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 notic- 

 ing 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 av- 

 erage, it may be about thirty-eight days. One or more of 

 the females are said to lay meanwhile; but the supernu- 

 merary eggs are placed outside the nest, and are supposed 

 to serve as nourishment for the callow brood. If such real- 

 ly be the case, we in this again see a wonderful provision 

 of nature, inasmuch as the chicken would be unable to di- 

 gest 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 vivi- 

 fied by the sun, arises probably from its habit of occasionally 

 quitting the nest in search of food, more especially as it gen- 

 erally 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 de- 

 stroys 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, " al- 

 ways use the precaution not to take away the eggs with their 

 hands (in which case the birds, who perceive it by scent, are 



