OF SOUTHERN AUSTRALIA. 27 



TREE-MARTIN 



(Tree-Swallow), 



Petrochelidoii nigricans, Vieill. 



Pet-ro kel-id' on 7iig'ri-ka7is. 

 Petros, a rock ; chelidon, a swallow ; niger, black ; cano, to sing. 

 CoLLOCALiA ARBOREA, Gould, " Birds of Australia," fol., vol. ii., pi. 14. 

 Geographical Distribution. — Areas 2, 3, 4, 5, 6, 7, 9. 



Key to the Species. — Under surface wliitish ; throat whitish, with 

 tiny black streaks ; frontal band sandy-buff ; rump whity-brown ; 

 tail forked ; nostrils without any superior membrane, round and 

 exposed. 



Of every hundred intelligent people who see Martins in the 

 woods or near bridges, I feel sure ninety- eight never distinguish 

 this species from the second Martin of the genus (P. ariel, Gld.) 

 That is because there is practically but one difference, which 

 in the distance is not discoverable without the aid of field- 

 glasses. One has the forehead rufous only, the other has the 

 forehead and crown rufous, these characteristics being 

 constant. They have similar habits, and very often occupy 

 the same natural surroundings. P. nigricans, as well as I 

 know, stays for the winter, and breeds in holes in trees, while 

 P. arid prefers creek banks and cliffs, against which they 

 build, or bridges, under which large colonies of nests are often 

 to be found. 



Being strictly arboreal, the Tree-Martin hunts in flocks, 

 feeding largely upon micro-insecta. In this respect it is 

 invaluable as an insect exterminator, rendering a service that 

 few other birds can equal. When each ninth or tenth 

 generation of the aphis comes into existence, the birds 

 display wonderful activity in their destruction. 



While the Fairy Martin feeds in a lower stratum, upon the 



