The Hebrides the nesting season is hardly overbefore 



the island-bred skylarks, so late in coming, 

 ' are on the Great South Road once more. 

 What with the habitual two and the not in- 

 frequent three broods raised in a single season, 

 particularly in Southern England, South- West 

 Scotland, and Ireland, and the enormous influx 

 of aliens from Northern and Central Europe, 

 our skylark population is at its highest, not, 

 as most people might think, in May, or even 

 about the season of the autumnal equinox, 

 but at the beginning of November, when 

 already the great tides of migration have 

 ebbed. Another puzzling problem is the 

 rhythmic regularity of the arrivals and depar- 

 tures of the incomers and the outgoers. For, 

 while the latter will not take the high-road 

 of the upper air till nightfall or at least until 

 dusk, the former travel by day : and the goings 

 and comings are so timed, or to observation 

 appear so timed, that about four o'clock on a 

 late October day the first cohort of the in- 

 vaders may in the wide lonely desert overhead 

 pass the first caravans of the exiles. In March, 

 again, the two currents may once more meet : 

 the home-bred birds are on their return, the 

 aliens are on the wing for the hill-pastures and 

 the vales and uplands of their native countries. 

 This will account for how, say in the Hebrides, 

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