366 THE ZOOLOGIST, 



the most mysterious of our birds. There is no doubt that it 

 passes a large proportion of the hours of darkness on the wing, 

 but for my part I can see no evidence strong enough to enable 

 us to look upon all these movements as migratory. And even if 

 we are ever able to prove that the calling birds are on migration, 

 we are faced with another problem in our knowledge that the 

 other Passerine birds do not migrate in this way. 



Up to now I can only imagine two possible explanations, 

 other than the unsatisfactory one of migration. The first is 

 that the note is not confined to the Eedwing, but is the common 

 property of many other Passerine birds when on migration. I 

 wish only to mention this, and do not hold the view. 



The remaining suggestion is that these noisy journeys con- 

 stitute a form of song. We have already in the Waterhen a 

 bird whose only '* song" consists of wild flights high in the dark 

 air above town and country, but so far as I know this song- 

 period is confined to spring and summer, and I have never 

 observed it before the first week in March or after the first week 

 in July. In January and February, when food is scarce, the 

 nocturnal calls of the Piedwing are rarely heard, but in the fine 

 weather of autumn and spring, when the birds are singing by 

 day in the tree-tops, we expect to hear their notes by night. I 

 have elsewhere (' British Birds,' iii. pp. 155-56) expressed my 

 opinion that bird song has no direct connection with sexual 

 affairs, and shown why it must be regarded as nothing but the 

 ebullition of superabundant energy ; and there would be nothing 

 unexpected in the discovery that the male Eedwing lets off his 

 superfluous vitality by wandering about in the dark skies of 

 autumn. Probably the final solution will be based on observa- 

 tions made in the breeding haunts of the birds, when they are 

 perfectly sedentary, for in this country the actual migratory 

 movements are certain to obscure the subject. We often read 

 that Eedwings migrate in hard weather, and read also that they 

 die of starvation at such times : it is just then that we rarely 

 hear their nocturnal voices ! And I know no better justification 

 for my notes than the easily ascertained fact that the majority 

 of ornithological writers have little or even no knowledge of 

 these noctivagations of the Eedwing. 



