ISOLATION 01' THK MALI. 63 



defined, until a belt of trees here, or ;m orehard 

 there, mark a rough and rarely passed boundary 

 line. 



I ,rt us take another example from the larger 

 migrants the lilack-tailed (iodwit, a bird 

 eon mum enough in the Dutch marshes but no 

 longer breeding in this country. On suitable 

 stretches of marsh land, numbers will be found 

 in proximity one to another after the manner 

 of the Lapwing, each male occupying a definite 

 space of ground wherein it passes the time 

 preening, searching for food, or in sleep 

 though at the same time keeping a strict watch 

 over its territory. Now the preference shown 

 for a particular piece of ground, and the deter- 

 mination with which it is resorted to, is the 

 more remarkable when we take into considera- 

 tion the specific emotional behaviour arising 

 from the seasonal sexual condition. This 

 behaviour is expressed in a peculiar flight. The 

 bird rises high in the air, circles round with 

 slowly beating wings above the marsh, and 

 utters a call which, as far as my experience goes, 

 is characteristic of the performance. The air 

 is often full of individuals circling thus even 

 beyond the confines of the marsh, for a male 

 does riot limit its flight to a space immediately 

 above its territory ; but nevertheless careful 

 observation will show how unerringly each one 

 returns to its own position on the breeding 

 ground, no matter how extensive the aerial 

 excursion may have been. And so, when the 

 males of the smaller migrants confine their 



