36 WILD BIRDS 



possible to doubt that this final shape must be a great 

 improvement on earlier shapes in the development 

 of this limb. If anything in the world evolved 

 through natural selection or other means, a swift's 

 wing evolved. 



Then there was the moulding of the machinery, 

 the muscles that drive the wing a great task for 

 evolution that must have been. The muscles of 

 natural flight are not many ; indeed, one great mus- 

 cle may virtually do the work ; but that muscle 

 was worked up to its perfection just as the feather 

 was worked up by unthinkable time, change, 

 detail. 



NEARING THE ZENITH 



May in its third week is nearly everywhere at its 

 best in coppices and lanes, and down by the brooks 

 and up on the downs. This perfection of May 

 is not quite the zenith of the year ; but it is very 

 near that fine point of time. The zenith of the 

 English year is before actual midsummer. It 

 has always seemed to me that, in the South of Eng- 

 land, the zenith includes a little of the end of May 

 and a little of the beginning of June, say about ten 

 days or a fortnight in all. 



The zenith is the short span when the freshness 

 and the fulness of spring and summer are at one. 

 Now, the prime of May comes just before that. 

 One of its great features is the leafing of the oaks. 

 When the leaf of these trees is fully out, the wood of 

 oak, beech, and birch with its underwood of hazel, 



