HIRUNDO URBICA. 



203 



like the " hairy caravan," but scouted and hurried along in little 

 detached parties or broods, and, sweeping low over the land 

 and water, crossed over to Africa at the narrowest passage — 

 sloping over from Tangier— and, from birds sent by his brother, 

 he was pleased to see some of those short-winged British 

 summer birds of passage about whose migrations so much fuss 

 had been made in his time ; " because, if these birds are found 

 in Andalusia to migrate to and from Barbary, those that come to 

 us may migrate back to the Continent and spend their winters 

 in some warm part of Europe." At all events, it is certain that 

 many birds come or go to Gibraltar in Spring and Autumn, 

 seeming to advance in pairs for the sake of breeding in Summer, 

 and retire in parties and broods on the approach of Winter — 

 the Eock of Gibraltar being the great rendezvous each way 

 towards Europe or Africa. Mr Bowdler Sharpe, of the 

 Zoological department of the British Museum, lecturing in 

 Manchester in 1875, said that swallows and swifts, like the 

 cuckoo, " when they leave our shores, go principally by the 

 route of the Nile valley down to the Cape of Good Hope ; 

 so it may interest you to know the winter home of these 

 birds." 



In 1770, Mr White thought it "no mean discovery to find 

 that our small, short-winged summer birds of passage were seen, 

 Spring and Autumn, on the very skirts of Europe, as a presump- 

 tive proof of their emigrations." With this in view, strange, 

 he could not get rid of the idea that swallows hibernated or 

 slept through winter like the hedgehog, the tortoise, or the 

 bat, instead of migrating. He alludes to this in no less than 

 ten of his letters on natural history. In one he says— " I am 

 now perfectly satisfied that swallows do not all leave this 

 island in Winter;" in another, "After all our pains and 

 enquiries, we are not quite certain to what region they do 

 migrate ; and are still further embarrassed to find that some do 

 not migrate at all f again, " Is it not more probable that the 

 next church, ruin, chalk cliff, steep covert, or, perhaps, sand- 

 bank, lake, or pool, may become their hibernoculum, and afford 

 them a ready and obvious retreat ?" In another, he " greatly 

 suspects that house-swallows have some strong attachment to 

 water, and though they may not retire into that element, yet. 

 they may conceal themselves in the banks of pools and rivers 

 during winter ;" which he iterates in another by saying — " At 

 least, many of the swallows do not leave us in the winter, 

 but lay themselves up like insects and bats in a torpid state, 



