SIRS,--Mr. N. D. Pullen, Mr. H. G. Hurrell and Miss N. C. Hicks (antea, Vol. xxxviii, pp. 206, 300 and 360) have drawn attention t o an interesting problem of behaviour. I have observed t h e " digging " in the bottom of the nest, as described by the above writers, at the nests of Raven, Chough, Greenfinch, Goldfinch, Chaffinch, Cirl Bunting, Spotted Flycatcher, Goldcrest, Mistle-Thrush and Blackbir...

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