I902. Reviews, 121 



cising its powers of obsen^ation, while still a nestling, in examining the 

 architecture of its nursery, and noting the materials emploj'ed in the 

 structure ; and (2) by watching some older birds of its own species at 

 work in the following spring with a view to copying their procedure. 



Adopting Mr. Dixon's own language, we may reasonably ask w^hether 

 this theory is "supported by a single particle of fact." There are, at 

 any rate, several facts which, to our thinking, conflict heavily with it. 



Taking first the supposed effects of observation during the nestling 

 stage, how can this hypothesis be reconciled with the fact that many 

 young birds are reared in the dark, and cannot study, because they can- 

 not see, the structure of their homes ? This is the case with some of 

 the most accomplished of our feathered architects, such as the Long- 

 tailed Titmouse, whose eight or ten youngsters, crowded tightly together 

 in the dark interior of their lichen-thatched dome, are debarred from all 

 possibilit)' of noting the position, the materials, or even the shape, of 

 the nest in which they are brought up. A still greater puzzle is afforded 

 by the South American Lochinias nematura, whose nest, situated at the end 

 of a narrow underground gallery, consists of " a vaulted globe with a 

 lateral entrance," whose " interior litiitig is of crossed batnboo leaves, woven in 

 a really artistic manner.'''' The inner lining of a domed nest built under- 

 ground must be exceedingly difficult to study as a pattern. Yet Mr. 

 Dixon makes no attempt to explain the transmission of the artistic 

 accomplishment oi Lochmias nemattira from generation to generation. In 

 fact, he entirely ignores the difficulty presented to his theory by the 

 exclusion of light from the interiors of so many nests. 



Nor can more be said for the second suggestion — that birds, when a 

 year or so old, supplement the knowledge acquired in infancy by watch- 

 ing experienced builders at work. With species which nest gregariously 

 this is, of course, possible ; but Mr. Dixon's theory requires that it 

 should be equally open to solitary nesters, and here the difficulties in 

 the way seem almost insuperable. Birds in the nesting season are extra- 

 ordinary prompt to repel any intrusion by others of their own species 

 within a fixed distance from the chosen site. Each pair appropriates 

 an area to itself, and fight savagely with all who invade that area. No 

 such thing as " a chiel amang us taking notes " is tolerated by building 

 birds in spring. And it is needless to point out how very close the 

 approach must be to enable one Grasshopper Warbler, for instance, or 

 Stonechat, or Blue Titmouse, to watch another at work. Instant detec- 

 tion and a severe mauling would be the inevitable consequence. 



Even among gregarious nesters, it not rarely happens that there are 

 no experienced builders for the beginner to watch. The House-Martin 

 builds a nest which, barring accidents, will last the bird's lifetime. Thus 

 practically all the nests of this species, in localities not subject to dis- 

 turbance, are first structures, the work of novices. 



We by no means question Mr. Dixon's statement that beginners often 

 build imperfect nests, and that the building faculty is improved and 

 developed by practice. Mr. Dixon Aonsiders this alone a sufficient and 



