302 



SCIENCE. 



[Vol. II., No. 31. 



These birds suftered no farther annoj'auce, and 

 reared their brood without mishap. 



Whj' should not these have utilized the ma- 

 terial for their nest which I offered, rather 

 than gather similar stuff from distant points ? 

 They could not have been frightened by any 

 odor attached to the material through han- 

 dling, as I was careful not to touch a particle 

 of it, using a pair of wooden tweezers in every 

 case. Neither did they see me carrying any 

 thing to or from their nests. As these, in 

 all cases, were nearly or quite completed, the 

 birds had necessarily become thoroughlj^ fa- 

 miliar with the surroundings, and doubtless 

 recognized the fact that these offered twigs 

 and the hair had suddenly appeared in, to 

 them, some unexplained manner, and the 

 mystery surrounding it made them suspicious. 

 Suspicion, I suggest, is a complicated mental 

 effort. Again : the sparrows were sorel}^ per- 

 plexed when a nest not of their building, but 

 of the same character, was substituted for 

 their own. Here, these birds exhibited fear ; 

 but finally the maternal instinct overcame the 

 timidity of the female, and she resolved to 

 brave the danger or solve the mystery, and 

 cared for her eggs as usual. The male bird 

 kept aloof for several days, I think ; but of 

 this I am not positive. These sparrows were 

 moved by conflicting emotions, — evidence, I 

 think, of an advanced degree of intelligence. 



Another series of experiments were as fol- 

 lows : finding a nest of the summer warbler 

 (Dendroeca aestiva) in a low alder, the foliage 

 of which was about one-third grown, I girdled 

 the supporting growths a few inches below the 

 nest. The leaf-buds withered, and the nest, 

 which under ordinarj' circumstances would have 

 been quite concealed from view hj the full- 

 grown leaves, was now exposed. The nest 

 was abandoned. 



The next girdling experiment was made on 

 the nest of a white-eyed vireo (Vireo nove- 

 boracencis) found attached to a low limb of a 

 small beech. The leaves quickly shrivelled, 

 and the nest, although just finished, was aban- 

 doned. 



A second experiment of the same sort was 

 tried, with identical result. 



A nest of the summer warbler was found in 

 a low shrub, containing young birds, and the 

 supporting branches girdled. The leaves with- 

 ered and fell, exposing the nest to full view. 

 The parent birds remained, and successfully 

 reared their brood. 



In these cases we have evidence of mental 

 operations of a more complicated character 

 than any exhibited by the sparrows. It is evi- 



dent, that in eyevy case, these birds, in selecting 

 the position for their nests, knew that the growth 

 of the foliage would afford a desirable, if not 

 necessary, protection to them. Finding that 

 the growth of the foliage had been checked, 

 that the little shelter at first afforded was dail3' 

 growing less, the}' foresaw that the nests, under 

 these circumstances, would be too much ex- 

 posed to be safe from molestation, and they 

 were abandoned, even after a full complement 

 of eggs had been laid. Can we explain this by 

 any other means than by using that ver}' sug- 

 gestive term ' foresight ' ? But mark : when 

 the same circumstance occurred after the 

 young had appeared, the claims of the brood 

 upon the parents were too strong to be over- 

 come, and the danger of occupying an exposed 

 nest was readilj' braved. 



Experiments of another character were as 

 follows : I placed a series of short pieces of 

 woollen yarn, fastened together at one end, 

 near the tree containing a partiallj' constructed 

 nest of a Baltimore oriole (Icterus Baltimore) . 

 These yarns were red, yellow, purple, green, 

 and gray. An equal number of strands of 

 each color were thus offered to the orioles as 

 building-materials. I purposely placed the red 

 and yellow strands on the outside of the tas- 

 sel-shaped mass, so that these would be first 

 taken, if the color was not objectionable. To 

 my complete surprise, the gray strands only 

 were taken, until the nest was nearly finished, 

 when a few of the purple and blue yarns were 

 used. Not a red, j'ellow, or green strand was 

 disturbed. Here we have an instance of the 

 exercise of choice, on the part of a bird, which 

 is full of interest. The woollen threads being 

 otherwise identical, it was the color only that 

 influenced the choice of the birds : thej' real- 

 ized that the red or yellow j'arns would render 

 the nest conspicuous, although well protected 

 by the 'foliage of the branch to which it was 

 attached. Why the green threads were not 

 taken I cannot imagine. As a result of this 

 experiment, I anticipated that the orioles 

 would reserve the brightly colored yarns for 

 the lining of the nest, and the gray and green 

 for the exterior. This was a result obtained 

 two years ago, when I tried a similar experi- 

 ment ; but the use of red yarn as a lining may 

 have been mereljr accidental. 



Out of mere curiosity, for I could not an- 

 ticipate what might be the result, I made a few 

 transfers of the eggs of one species into the 

 nest of another bird. The results were not, 

 however, particularly suggestive. I placed 

 the eggs of a cat-bird (Mimus caroUnensis) in 

 the nest of a song- thrush (Tui'dus mustelinus) , 



