294 PROCEEDINGS OF THE ACADEMY OF 



constructed and tastefully arranged. But, as I had anticipated, 

 the mother deserted her offspring ; the love for home predomi- 

 nating over ever}' other feeling. 



These deviations from the usual style of nest building by the 

 pewee would seem to argue against the belief generally enter- 

 tained, that instinct, being a positive determination given to the 

 minds of animals for certain purposes, must necessarily be perfect, 

 when viewed in connection with those purposes; but to say that 

 they doubtless iropl}' a chavge of instinct is to perplex the under- 

 standing by a perversion of language. But to ascribe these 

 changes to the operations of reason influenced b}'^ motives, does 

 seem to be the most rational view to take of the subject. That 

 reason does enter into the inferior creatures, and dictate man}' of 

 the changes of habit which mark their career, has been shown in 

 many instances ; but I cannot forbear to record one which came 

 under mj' observation in the spring of 1871. While watching a 

 pair of Ampelis cedrorum, Baird, engaged in the building of a 

 nest on a branch of an apple tree, it occurred to me, that by sup- 

 plying them with materials I might secure a nest neater and more 

 compact than those usually made. The birds entered into the 

 project with readiness, and carried away every piece of colored 

 string and cotton fabric with which I supplied them. After I had 

 ceased to furnish the materials they would fly repeatedly to the 

 branch where the articles were deposited, as if imploring my ser- 

 vices. The result was a nest firmer, more symmetrical, and more 

 elegant in proportions than any I had ever observed. If instinct 

 had been the controlling principle in this case, the birds would 

 not have given my labors so much attention; but admitting that 

 they had been actuated by reasoning faculties in their selection, 

 the whole thing is perfectly plausible. Instinct is always the same 

 thing ; it never advances, never retrogrades ; but reason tends to 

 improvement, when it can serve a good purpose. 



As the nests which form the subject-matter of this paper were 

 found within a short distance of each other, it would seem that 

 circumstances peculiar to the neighborhood had rendered a de- 

 viation from the common form necessary. Observation teaches 

 us that when danger or any other circumstance renders a change 

 in the character of the nest necessary, that deviation is made in 

 an equal degree and in the same manner by all the birds of one 

 species, and that it does not extend beyond the limits of the region 

 where alone it can serve a good purpose. 



