BRITISH WARBLERS 



the fact of the bird flying from place to place, and even 

 making initial attempts at construction, we seem to be pre- 

 sented with evidence of conscious deliberation. Hence some 

 may affirm that she carries in her imagination a mental image 

 of the nest she is about to construct, and thus decides in 

 advance as to the relative merits of the various situations. 

 But a young bird is capable of constructing a nest antecedent 

 to experience, and manifestly has no mental image before it, 

 and cannot well make use therefore of any such complicated 

 process of reasoning. Is it then necessary to demand such 

 a power for the adults ? 



The nest is placed in various situations — in perpendicular 

 osiers, amongst common nettles {JJrtica dioica), cow parsnip 

 (Heracleum sphondylmm), meadow-sweet (Spiraea ulmaria), 

 wormwood (Artemisia absinthium), dogwood (Cornus san- 

 guined), tall grass, and not infrequently in young ash plants. 

 In giving the results of his long experience with these birds 

 in Oxfordshire, Mr. Warde Fowler writes as follows : xu But 

 here I may remark that it is not every kind of osier willow 

 that suits our bird ; I have never found the nest in any but 

 the Salix triandra, which sends up pliant perpendicular shoots 

 quite close to each other. The other osier to be found in all 

 withy beds (8. viminalis) is in every way less suitable. If 

 the osiers in the favourite breeding place have been cut, and 

 the season is late, the birds will be in serious difficulties, and 

 will search for suitable sites in hedges and ditches, and have 

 recourse to nettles, wild parsnip, or even beans, as we have 

 seen. Here, of course, they run far greater risks than in the 

 dense vegetation of the osier-bed, where I have hardly ever 

 known a nest destroyed or even discovered by the ploughboys 

 who are constantly about the spot. The difficulties met with 

 by my birds during the last few years lead me strongly to 

 believe, apart from other evidence, that the Marsh Warbler 

 is not, and cannot be, a more abundant bird than we 



1 Zoologist, vol. x, p 406. 

 44 



