A SHORT STUDY OF BIRDS' NESTS. 125 



suming decidedly avian features, it certainly bore no re- 

 semblance to any living bird, the oldest form of which was 

 long since evolved from a still more primitive avian, and 

 at the same time distinctively reptilian, creature. These 

 changes having been wrought in the birds themselves, it 

 would be strange indeed if there had not been a corre- 

 sponding want of fixity in their habits. 



As to the general correctness of the views of Mr. 

 Wallace concerning the motive that causes certain birds 

 to build nests of a particular pattern, I have no criticism 

 to make. Suffice it to say, that the results given in the 

 following pages will show that, to a certain extent at 

 least, his views will apply to our birds. With these cau- 

 tionary remarks we are now ready to take up the results 

 of my short studies of the nests themselves, which were 

 originally made several years ago, but which have been 

 verified during each succeeding summer. 



Having carefully examined the nest of a particular 

 kind of bird, which seemed to agree most nearly with 

 the published descriptions, I then noted each nest found, 

 and marked the amount of variation in the construction 

 and position. Take, for instance, the nest of our common 

 robin. Here we have a nest largely constructed of coarse 

 twigs and grass, lined with a " cup-shaped fabric of clay 

 or mud," this mud being covered with finer grass, horse- 

 hair, and occasionally a few feathers. It is an excellent 

 nest to study, as it shows fully the amount of variation 

 practiced in their construction. During the spring and 

 summer of 1873 I found thirty-two of these nests in an 

 area of about four hundred acres. Of these thirty-two I 

 shall speak, principally with reference to the care exhib- 

 ited in the mud lining, and refer but incidentally to their 

 positions. Eleven of them were what might be called 

 " typical" ; as in them the mud lining was complete, ex- 



