258 FRANCIS H. HERRICK 



the inference that measures of this sort are adopted to save 

 the young from falling out of the nest receives no support. 



Compound or superimposed nests. We have been considering 

 simple, individual nests, but have earlier referred to aggregated 

 nests, or those composed of closely associated units, such as are 

 made by the sociable grosbeaks (see p. 184 of part I), or the 

 waxwing {Dulits dominiciis) of San Domingo, as well as to com- 

 pound nests representing a more or less extended series of 

 "supra" or " infraimposed " structures, as in certain gulls, 

 eagles, doves, warblers, vireos and weaver birds, whenever an 

 old nest, whether of the same or of different individuals or 

 species is used more or less completely as the site of a new one. 

 Under such conditions the greatest variation in size and weight 

 may be expected. 



In illustration of the foregoing remarks, compare the first 

 season's nest of a robin, with the same when used for a second 

 brood, the nest of a herring gull " repaired," and occupied 

 the following year, as was reported by Audubon -* ajnd has 

 been noticed by others since, the eyries of the eagle and fish 

 hawk, which are occupied for successive years, and which vary 

 in height in proportion to their age, within the limits of stable 

 equilibrium. This increase is to be observed in the white headed 

 eagle under certain conditions, but would not hold w^here the 

 nest was diminished through the process of natural decay. 

 The greatest recorded period during w^hich a given nest and 

 nest site has been continuously occupied, is considerably over 

 the century mark. Thus, according to Newton, an eyrie of 

 the falcon {Falco peregrinus) on Arasaxa, a hill in Finland, was 

 in continuous use for 119 years (1735-1855), and an earthenware 

 bottle or its substitutes, in the branches of a tree in a garden 

 at Oxbridge, England, was known to have been used by the blue 

 tit {Parus ccerulens) from 1779 to 1888. We have finally to 

 notice the remarkable " storied," or serially superimposed nests 

 which a yellow warbler or vireo will sometimes build, whenever 

 their breeding cycle has been repeatedly broken by fear, and the 

 site of the old nest is successive!}^ chosen as that of a new one.^* 

 In this w^ay, as we have show^n, the parasite's eggs are admirably 

 " concealed," and its designs frustrated. 



'^ Op. cit., vol. iii, p. 590. 



^* For illustrations and fuller discussion see Instinct and Intelligence in Birds. 

 Popular Science Monthly. New York, 1910, vol. Ixxvii, p. 87-92. 



