so 



THE NIDIOLOGIST 



of my acquaintance, so frequentlv abused 

 as the little blue-eyed sulyect of this sketch. 

 However, although some unobserving 

 writers claim that nest owners do not re- 

 cognize the difference in the color and 

 shape of the alien eggs and their own, this 

 little bird certainly demonstrates that it 

 knows the cheat, and gives the best of evi- 

 dence of reasoning powers in compassing 

 the destruction of unsought additions. 

 Not infrequenth' nests of this species are 

 found which contain a Cowbird's egg en- 

 tombed in the body of the nest, the 

 thoughtful birds having built a deck or 

 floor over the egg of the plebeian of im- 

 moral views, and thus 

 protected themselves for 

 the time from interlopers. 

 These double-decked 

 nests are not rare, and I 

 doubt not there are many 

 of them at the present 

 moment in collections, 

 where their peculiarity is 

 unsuspected. Whenever 

 a Yellow Warbler's nest 

 is found containing four 

 or less incubated eggs, and 

 one has reason to think 

 the complement laid, it is 

 wise for the observer to 

 carefully separate the low 

 er layers of the structure 

 and search for the other 

 eggs of the set, for it not 

 rarely happens that the 

 pair have immolated one 

 or two of their own eggs 

 in order to cover over 

 one or two aliens. 



A nest, now before me, exhibits the skill 

 of these reasoning birds in thus relieving 

 themselves of an unsolicited burden. The 

 nest is not of much greater depth than the 

 normal nest, but is never-the-lessof two sto- 

 ries. The upper nest or floor contained 

 three eggs well incubated. The condition 

 would not have been noted had I not in re- 

 moving the nest accidentally broken a con- 

 cealed egg of the Cowbird, and as it was 

 addled the discovery was quickly made. 



The eggs of the Yellow Warbler are al- 

 most invariably five in number, but some- 

 times only four, and in rare cases six. In 

 one instance I found five eggs of the right- 

 ful owner and three of the Cowbird, mak- 

 ing a decided "nest full." It is safe to 

 say that some attempt would have been 



made to head off the nuisance if the aliens 

 had been laid early during the deposition 

 of the set, but as there was no help for it 

 the little Warbler accepted the additional 

 duty and was trying her best to cover the 

 eight eggs. The larger eggs had gravi- 

 tated to the center of the nest, as they al- 

 ways do, and the Warbler's eggs were 

 crowded to the sides. 



Occasionally three-storied nests are found, 

 and I should not be greatly surprised if 

 four-storied ones were recorded later. In 

 one nest which I met with, an anxious 

 Cow Bunting had assumed possession pre- 

 maturely, and the egg was laid before the 



YOUNG 



COWBIRD IN WARBLER'S NEST 



nest was completed. This was covered 

 and the nest finished, and two eggs were 

 deposited to the credit of the happy War- 

 blers. Two Cowbird's eggs were then laid 

 beside the smaller ones. After this imposi- 

 tion, the determined pair, perhaps from for- 

 mer year's experience with these pests, im- 

 mediately began a second time to evade the 

 encroachments of the spoliators, and en- 

 humed their own eggs with the unsought 

 additions. When discovered, their work 

 of love had advanced to the stage where the 

 remainder of the .set reposed in the upper 

 story. 



The three-storied nests are quite high, 

 generally all of one-half higher than the 

 proper nest, and I have seen them of twice 

 the height. Occasionally the nest widens 

 as it is built ud, as in the illustrated exam- 



