August, 1909. The Irish Nahiralist. 16 1 



THE USE OF DOMED NESTS. 



BY C. B. MOFFAT. 



Of the hundred and thirt3'-two kinds of birds which breed in 

 Ireland only eight build (normally) the kind of nest known as 

 '•' domed '" — that is to say, with the top roofed over, and a hole 

 in the side serving as entrance. Three of the eight are the 

 closely related '' leaf-warblers " — the Chiff-chaff, Willow- Wren, 

 and Wood- Wren. The other five, though all passerine birds, 

 represent as many distinct families — the Dipper the Cinclidce, 

 the Long-tailed Titmouse the Paridse, the Wren the Troglod}'- 

 tidae, the House-Martin the Hirundinidae, and the Magpie the 

 Corvidse. Why these eight, and no others, should build domed 

 nests is a question that must often have puzzled reflective 

 ornithologists ; and I do not think that a satisfactory answer is 

 provided by the theory which that eminent thinker Alfred 

 Russel Wallace put forward in one of his well-known essays 

 in 1S68, that those species of birds in which tho^ females as well 

 as the males are brightly or conspicuously coloured need and 

 adopt a type of architecture that will make the sitting bird 

 invisible. Dr. Wallace argues — and supports his case with 

 facts drawn from a very extensive survey of the birds of the 

 world — that such birds, as a rule, either construct domed nests 

 or place their nests in holes. But even if we admit the entire 

 truth of this theory it does not cover the Irish (which 

 correspond with the British) cases. For of all our eight dome- 

 constructing birds, only one — the Magpie — can be described 

 as having a conspicuous t5'pe of colour ; and it would, I think, 

 be difficult to contend that the soberly-clad Wren and Chiff- 

 chaff can, in consequence of their hue, stand more in need of 

 a concealing dome during incubation than the hen Blackbird 

 and Goldfinch, which are content with open nests. 



I wish now to draw attention to one purpose which the 

 domed nest in this country certainly serves, and which is 

 probably of greater importance to most of our dome-construct- 

 ing species than the small amount of additional concealment 

 that the dome may give them. 



Of our eight dome-builders, two, the Wren and the Long- 

 tailed Titmouse, are notorious for the large numbers of eggs 

 they lay to a clutch. Ten is no uncommon number for the 

 former, and twelve or more for the latter, even in Ireland, 



A 



