Vol. XVIII 



1919 



1 Thomson, Nesting Habits of the Grass-Warbler. igg 



The Nesting Habits of the Grass^Warbler (Cisticola 



exilis). 



By Donald Thomson, R.A.O.U., Canterbury (Vic.) 



Down among the grassy river flats which border the Yarra River 

 for many miles of its upper reaches, where acres of tall seeding 

 docks and luxuriant grass lands are studded with innumerable 

 quiet lagoons, whose margins are hidden by a wealth of tall 

 bulrushes, sedges, and other water plants, the little Grass-Warbler 

 {Cisticola exilis) delights to have its home. 



Even before one actually reaches the home of this beautiful 

 little bird, its sharp, wheezing, but not piercing call is plainly 

 audible, wafted to the ears by soft spring breezes. At first it 

 appears to come from the clear azure above, then from the right 

 or left, and then when the bird at last is seen it will probably be 

 in quite a different direction from that from which it at first 

 appeared to come. Thus it would seem that this bird has the 

 wonderful natural gift of ventriloquism. 



Approaching carefully, seeking cover among the tall docks, and 

 keeping very still, the birds at last are reassured. Then from the 

 shelter of a clump of reeds a bird flits and settles near at hand. 

 His colour is a dark rusty brown, with darker markings of black 

 on the head, back, and wings, and the pale buff of the breast, 

 fading almost to white on the throat, is clearly seen. Seeing 

 that all is safe, the bird has a high flight in the air, at the same 

 time uttering the loud wheezing cry, and finally alighting on a 

 clump of rushes not far away from his starting-place. The aerial 

 journeys are taken very often during the hot spring days and in 

 the quiet stillness after sunset. These birds seldom enter the 

 clump of vegetation in which their nest is hidden by direct flight, 

 even if certain of security from observation. They alight some 

 little distance away and then " creep " from stalk to stalk, always 

 low down, until the nest is eventually reached. 



At last, as the November sun sinks to rest over the western 

 gums which border the river, a still quietness reigns everywhere. 

 Even the little Grass- Warblers are not so noisy now. On almost 

 every clump of finely-grown reeds a bird sits, swaying on the 

 topmost seed-head. As if conscious of the presence of a watcher 

 — I shall not say enemy — they flit from clump to clump uneasily, 

 always selecting a tall plant on which to alight. Slowly, very 

 slowly, a bird approaches my " lair." He flies to within a few 

 feet of my hiding place, always to make a short aerial journey, 

 landing a little further away. Returning slowly once more, he 

 at last evidently makes up his mind to take the risks and return 

 " home," for, diving into the undergrowth, he is lost to view. 

 Soon a bird would appear close at hand once more, this time with 

 some " down " or other building material in its mouth, and, 

 flitting about, would finally vanish below. Most of the nest-building 

 appears to be done at sunrise and just about sunset — that is, in 

 the cooler and quieter hours of the day. 



