BALTIMORE ORIOLE 251 



been built, was found still to contain a few horsehairs. These must have been 

 quite difficult for the bird to find, for the farm is now worked only by tractors. 

 And in a nest taken this autumn in Sewickley no horsehairs whatever were to be 

 found. The nest was composed chiefly of fibres of the bark of Indian hemp 

 (Apocynum). Felted in toward the bottom of the nest were the hair-like pappi 

 of dandelion seed; over this was laid the fluffy, cottony covering of willow seeds 

 (the nest was in a weeping willow tree) ; and the lining of the bottom of the nest 

 was of rather stiff fibres of grape-vine bark. 



Audubon (1842) says that in Louisiana the bird uses Spanish moss 

 chiefly as a building material. In this warm climate, it weaves the 

 walls so loosely that they permit the passage of air, and little lining is 

 added. 



It has long been a matter for wonder among naturalists how the 

 oriole can accomplish such a finished piece of workmanship in con- 

 structing its nest, work which seems to demand a conscious planning 

 far beyond the resources of a bird's mind. The older writers speak 

 rather vaguely of the weaving process and have little to say about how 

 the bird employs what Audubon calls his "astonishing sagacity." 



Francis Hobart Herrick (1935) has recently made a careful, in- 

 tensive study of nests of the Baltimore oriole, watching their construc- 

 tion from the tying of the first string to a branch until the nests were 

 completed. The following summary embodies the main steps in the 

 workmanship of the bird as described in Dr. Herrick's account, a 

 comprehensive paper of absorbing interest. He says: 



The first strands of bast, which are apt to be long, are wound about the chosen 

 twig rather loosely with one or more turns, or perhaps they are passed only once 

 across or around the branch; but subsequent modes of treatment tend to draw 

 these threads tighter, and as their free ends are brought together, other fibers are 

 added. From such simple beginnings a loose pendant mass or snarl of fibrous 

 material, which I have called the primary nest mass, is slowly formed, but it is a 

 long time before it takes on the semblance of a nest or nest-frame. * * * 



Behavior at each visit, after a certain number of strands had been laid and joined, 

 was essentially the same, the oriole usually bringing in but a single fiber and carry- 

 ing it around the support and working it into the nest mass by what I have called 

 shuttle movements of the bill. Clinging to the principal twig, hanging often with 

 head down, and holding the thread, the bird makes a number of rapid thrust-and- 

 draw movements with her mandibles. With the first thrust a fiber is pushed 

 through the tangle which soon arises and forms the growing mass, and with the 

 next either that or some other fiber is drawn loosely back. * * * 



While these shuttle movements are, first and last, very similar, and almost 

 equally rapid at all times, the number made at each visit tends to increase with 

 the growing complexity of the product. At least one hundred shuttle 

 movements were sometimes made at a single visit, but these were often so rapid 

 that it was impossible to count them, and many of them must have been abortive. 



In all this admirable work there was certainly no deliberate tying of knots, 

 yet, as the sequel will show, knots were in reality being made in plenty at every 

 visit. There certainly was no deliberate directing of the thread, as when a coat 

 is mended or a hammock is woven in a certain way by human hands. The work 

 was all fairly loose at first, yet naturally some of the threads became drawn more 



