402 INFLUENCES OF CULTIVATION 



House Martin making its home in the darkness of a cavern, 

 betrays the secret of its original haven, before man led its 

 kind to alter their ways by supplying new building sites. 

 That the preference for man's dwellings seems to be almost 

 a primitive instinct of the Swallow's nature is shown by the 

 unanimity with which different species of Swallows in all 

 parts of the world- in Europe, China, India, South Africa, 

 Australia and America seek out the habitations of men 

 for their nesting-places; and by specific cases, such as that 

 mentioned by Dr Richardson as occurring in 1825, when Cliff 

 Swallows (Petrockelidon) of North America, left their native 

 cliffs to build under the eaves of a house at Fort Chapewyan 

 "the first instance of this species of Swallow placing itself 

 under the protection of man within the widely extended 

 lands north of the great lakes." Sometimes necessity com- 

 pels a reversion from even so well established a habit: in 

 the deserted towns of France, where during the War all the 

 buildings have been demolished, Swallows have taken to 

 building in dug-outs and in trees at least a dozen nests 

 having been seen in a single standing poplar tree. 



The strength of the new instinct in the House Martin at 

 the present day is indicated by the numbers of nests which 

 are annually occupied on favoured houses. On a labourer's 

 cottage of brick and tile in a village near Stratford-on-Avon, 

 the Martins' nests were all destroyed in 1915, but in the 

 summer of 1916 the birds returned in such numbers that 

 the cottage sheltered 86 nests, so closely packed that the 

 parent birds had in some cases to feed their young in turn 

 from the door of their neighbour's nest. Mr O. H. Wild 

 has drawn my attention to a similar congregation of 

 Martins' nests on a small house on the southern slopes 

 of the Pentland Hills at Baddingsgill in Peeblesshire. 

 There during the past six years, nests have varied in number 

 from 56 to about 70, in 1916 the occupant counted 74, and 

 in the spring of 1917, before the year's migrants had arrived, 

 I saw the old nests plastered thickly under the eaves, from 

 five to seven being occasionally crowded together between 

 the ends of a couple of rafters. 



This curious change of habit in the Martin is interesting 

 as an illustration of the subtle influence of civilization on 

 the choice of the bird, but the examples just cited indicate 



