142 Sketches of Some Common Birds. 



owner will oust the alien egg from the nest with little 

 ceremony when she returns. We sometimes find an Qgg 

 of the owner on the ground near a nest containing an egg 

 of the cowbird, and it is no unusual occurrence to find an 

 egg of the cowbird lying near a nest of a species regularly 

 imposed upon by the parasite. 



Each female of this species lays at least four eggs, in all 

 probability, sometimes depositing them all in one nest, as 

 is inferred in such instances from the great similarity of 

 the parasitic eggs found in one nest. It is not uncommon 

 to find from one to four eggs of the cowbird in a single 

 nest. A female cowbird, which had been wounded, was 

 captured and kept for a time in captivity by Dr. Morris 

 Gibbs, and within eighty-four hours after its capture it 

 deposited four eggs at irregular intervals. This spring I 

 found a nest of the towhee containing two eggs of the 

 owner and four eggs of the parasite, and two each of the 

 four were so markedly similar that it was fair to conclude 

 that two cowbirds had deposited two eggs each in the 

 nest. Other observers have been impressed with the idea 

 that the same female frequently places two or more eggs 

 in one selected nest. In this connection I quote from the 

 article mentioned as written by Dr. Morris Gibbs : " In 

 every instance that I have recorded in my note-book, and 

 they are numerous, I have had it impressed upon me that 

 the cowbird is influenced by the size of the nest in laying 

 a large number of eggs in one nest, rather than by the 

 number of eggs to be laid by the legitimate owner. Of 

 course what we term instinct in the lower animals asserts 

 itself in some way in these cases, and the cowbirds judge 

 us to the ability of the contemplated foster parents to 

 provide for the unwelcome nurslings, by the size of the 

 nest. Once I met with a bluebird's nest in a very large 

 excavation, containing five blue eggs and four speckled 

 ones, and in this case the speckled eggs were evidently 

 laid by the same female, judging from the size and mark- 

 ings." 



As has been stated, sometimes the returned owner of 

 the nest, indignant at the violation of its home, lifts the 

 egg of the cowbird from the nest and places it at a safe 

 distance, or pierces the shell with its bill and thus carries 



