NESTS AND NEST-BUILDING IN BIRDS 365 



The nest, the building of which has been described, was at- 

 tached as we have ccen at six points, beginning with the first 

 two, shown in figure 19, and passing from left to right until 

 eventually the rim was enclosed; the sixth twig being a sub- 

 ordinate branch of the first and lying below the level of the 

 primary supports, does not enter into the rim, but is worked into 

 the wail, lower down. All told these six twigs bear about 200 

 slender strands of bast ; some are simply passed over the support 

 with several inches clear and worked into the nest at either 

 end (as in iv), while many are wound closely about the twigs 

 and both interwoven and knotted in the thinner web of the rim. 

 As to their strength we found that they could easily sustain 

 a weight of eight pounds. The strength of the wall itself is 

 best seen by attempting to break through it or tear it apart. 

 It is probably no exaggeration to say that the walls of some 

 of these nests contain 10,000 stitches and thousands of knots 

 and loops. If we allow 40 working hours and but five visits 

 to the hour, I think 20,000 " shuttle movements," pushing 

 a thread through and drawing it or some other thread back, 

 would be a moderate estimate of one phase of the activity of 

 an oriole in weaving its nest. 



The oriole's stitches bear as little relation to the deliberate 

 work of the tailor in first knotting his thread and then sewing 

 his garment, as the molding and turning movements of a robin 

 bear to the hand work of a potter. The oriole can and does 

 tie as good a knot as tailor or sailor, and the robin may "turn " 

 as true a cup as that thrown on a potter's wheel. The results 

 are indeed similar, but the impelling impulses \^'idely difterent. 

 In the case of the birds the results are so clearly due to a stereo- 

 typed form of behavior detemiined by heredity in all essential 

 respects, that any discussion of intelligence involved much 

 above the plane of association is superfluous. Considering 

 the rapidity and persistence of the shuttle movements, is it any 

 wonder that the knotting and interlooping of the threads pre- 

 sents an irregularit}^ and complexity w^hich baffles description? 



Nest Building in Other Species. — To describe in detail the 

 building habits of Chebecs (Empidonax minim us) , bluebirds {Sialia 

 sialis), and chipping sparrows (Spizella socialis) would involve 

 much repetition, and we can refer to a few only of the most 

 interesting facts observed. 



