BIRDS AS ARCHITECTS 31 



such as the two mentioned, and if it made all possible tests of this instinct, 

 is off the ground, it may be obvious and in vain. A pair used to come 

 from immediately above, but is never annually to my garden. A little ama- 

 prominent as a mass against the sky. teur carpentering in the winter re- 

 It resembles a chance collection of duced their hole to the proper size, 

 dead vegetable matter either in coarse without adding any appearance of 

 grass or in the lower tangle of the human craftsmanship, but they de- 

 undergrowth, with which the thicket serted it for a neighbouring tit's hole, 

 grasses mingle. Both these birds are that was too large, and plastered that 

 exceptionally cautious in approaching up instead. Several holes were cut 

 their nests ; and the woodwren in in their old tree the next winter, some 

 particular, hardly ever enters until she too large, and some the right size ; 

 has perched a moment on some twig they employed in time every hole 

 perpendicularly above the nest ; and as except those the size they required, 

 watched by the field glasses she seems I am at an entire loss to explain the 

 to give far more attention to the additional instinct, nor, to my know- 

 neighbourhood of the nest than to ledge, has it yet been explained, 

 any obvious danger a little distance The missel-thrush shows an in- 

 off. If the ground just round the nest teresting evolution. Allied to the 

 is clear she will drop to it like a stone thrush and the blackbird it builds a 

 in full view of the watcher ; but put very similar nest for very similar needs, 

 some tiny article from your pocket and in all habits resembles its kindred, 

 in the grass near the nest, and it will But it happens to breed a month 

 be an hour before she can muster earlier than they do, so far as any 

 courage to descend and investigate. rule can be framed ; at any rate it is 

 The only bird that nests in holes the earliest to nest of the three. When 

 and has any peculiarities is the nut- the thrush and blackbird begin to 

 hatch. The others choose any hole nest there is either greenery or a hope 

 that is either inaccessible or concealed of greenery coming to aid them in 

 by position, and make a few rough their concealment before the young 

 preparations for comfort ; the nuthatch have flown ; the missel-thrush on 

 insists on choosing a hole too large the other hand, starts earlier and ob- 

 for it. and reducing it to the exact size viously knows that the foliage will 

 required by clay plastering. I have come too late to serve it. As a result 



