622 CYPSELUS MURAKIUS. 



This I take to be the juncture when the business of generation 

 is carrying on."" Such phenomena certainly present themselves, 

 yet it is not by any means improbable that they are merely in- 

 dicative of the hostility of rival males ; for we often see larks 

 fighting in the air, and so keenly engaged that they sometimes 

 descend " many fathoms " before separating ; and I have ob- 

 served eagles struggling on wing, and emitting " a loud pierc- 

 ing shriek," although no one could reasonably suppose them to 

 be then copulating. 



In the longest days of June, the Swift comes abroad as early 

 as half-past two, and I have seen it flying as late as half-past 

 nine. In the summer of 1 837, I made some observations on 

 its mode of flight, which I here transfer from my note-book, 

 they having always been written down on the spot. 



There, on this beautiful evening of the 1st of July, when 

 the whole sky is cloudless, but overspread with a filmy haze, 

 through which the setting sun displays his broad red disk, the 

 Swifts come screaming in troops over the house-tops. They 

 fly so rapidly that you can scarcely suppose them to be search- 

 ing for prey ; yet now and then a sudden turn indicates the 

 capture of a fly. When they separate, they cease from their 

 noise, and for a while speed along in curves rapidly moving 

 their wings ; but now three or four sweep past in succession, 

 as if one had in view to overtake or outstrip another, and their 

 shrill cries form a continuous scream. Another band dashes 

 into the line, and they mingle together for a moment, then 

 separate, and fly off solitarily. Their cries, shrill and some- 

 what harsh as they are, seem cries of joy, for they are loudest 

 and most frequent when they fly close together ; and certainly 

 they are not indicative of animosity, for Swifts on such occa- 

 sions never fight or attempt to injure each other. Again they 

 shoot past ; but by this time we have enough of them. In half 

 an hour, they will have retired to their holes, and when our own 

 flight of life is over, we shall follow their example. Now, if elec- 

 tricity be the exciting cause of all this screaming, let us take 

 note of the weather, and see if it will lead us to any result. 



On the 2d July, the sun shone brightly till about eleven, 

 when the sky became overcast with a thin blue stratus, the 



