ORNITHOLOGICAL OBSERVATION IN ICELAND. 223 



circular depression, closely resembling that in which the eggs 

 are afterwards laid, is produced, and it places in this, moreover, 

 some scanty materials, such as grass-blades. The general idea is 

 that the cock bird alone does this, but I have seen both sexes act 

 so, as a sequel to coition ; and also make little pecks at the ground 

 at or beside the places rolled on. The most marked features of 

 these performances, which seem clearly sexual, are the pressing 

 of the breast against the earth, with a sort of rolling motion, and 

 the strong downward pressure of the tail, or rather anal parts 

 generally, with spasmodic movements, such as, in the male, 

 accompany coition. The wings are drooped, extended from the 

 sides and slightly quivered ; and with these actions the pecking 

 at things on the ground is also conjoined. The action here noticed 

 with the tail as well as with the wings is a perfectly useless one, 

 (at any rate, as it is practised, for the bird's hinder parts are 

 tilted into the air), in connection with the making of a shallow 

 pit or hollow ; but it is effectively employed by the Blackbird in 

 shaping the rim of its well-built and very differently placed 

 nest. There is also here the same pressure and movements of 

 the breast and wings, by which the cup is shaped, and, whilst 

 thus acting, the bird has a very curious appearance, for it seems 

 to be in a sort of ecstatic state rather than exercising a purely 

 mechanical craft. I cannot but think it odd, if nidification has 

 been purely architectural in its beginnings, that any bird 

 should have thought of employing its tail in this way. It may 

 not be beyond the possibilities of intelligent adaptation (though 

 we do not see many such), but I must look at the manner as 

 well as the matter, and find it easier to suppose that one and 

 the same cause lies at the root of these movements in the 

 concupiscent Peewit, the building Blackbird, and the incubating, 

 or fostering, Merlin — et sic de ceteris. If the nest, as an adapta- 

 tion to the needs of the young and the practice of incubation, 

 grew out of the place — at first unmodified and then strewed 

 with some light litter of flung-about materials merely — where 

 birds were accustomed to pair, we can see why, in the case of 

 some species (we do not, by any means, yet know how many), 

 the old habit and the old association of ideas is continued. 

 Otherwise, however, these facts are not easy to explain. Archi- 

 tecture, properly so called, cannot be supposed to flow naturally 



