THE MARSH-WARBLERS 79 



distinct in their usual form, nests of the two species occasionally 

 approximate not only in structure and material, but also in the 

 nature of their site and surroundings. 



According to Naumann, the reed-warbler does not, as a rule, 

 build again if the first nest is destroyed, although he records an 

 instance of a pair doing so. 1 So keen an observer as Naumann 

 must have had good reason for making this statement, but I doubt 

 if it would bear investigation. Systematic destruction of several nests 

 in a definite area e.g. an isolated reed-bed would be a reliable test, 

 but the drastic nature of the process would hardly commend it. 2 It 

 is a fact well established by observation that the marsh-warbler not 

 only replaces a destroyed nest by a fresh one, but builds again close 

 to the same spot. It has even been known to do what practically 

 amounts to building a new nest on top of a disturbed one. Mr. 

 Warde Fowler records the finding of three nests with eggs on the 

 20th and 21st of June 1898. "From one of these nests the eggs 

 gradually disappeared between June 25th and 28th when I cut it 

 out of the meadowsweet, and found the egg of a cuckoo buried 

 under a fresh lining. . . .'As it was clear that the removal of the 

 marsh-warbler's eggs was not due to any human being, it may pro- 

 bably be put down to the cuckoo." 3 The inference is a fair one, as 

 any other marauder would hardly have left the cuckoo's egg. It is 

 fair to assume also that the marsh-warbler abandoned the nest in 

 its altered state i.e. minus its own eggs and plus that of the cuckoo 

 and instead of building afresh, put in the new lining on top of 

 the cuckoo's egg with a view to using it for a fresh clutch. In 1909 

 I kept fairly close observation of the operations of a pair of marsh- 

 warblers in a small marsh near Cambridge. Their first nest was 

 found on June 14th, and contained four eggs and one of a cuckoo. 

 The latter was removed, and, whether due to this or not remained a 



1 Naumann, Vb'gel Mitteleuropas, ii. 68. 



" H. S. Davenport has noticed that in building the second nest the reed-warbler uses the 

 material of the first." F. C. R. Jourdain (in litt.). 

 3 Zoologist, 1006, p. 403. 



