WILLOW WARBLER
morning of May 10th, noticing that a female was wing-flapping and that the male was close beside her. I examined the nest and was surprised to find the female sitting; she fluttered off in fact at my approach. The mystery, however, was soon explained, for the second female, the bird that was excitedly flapping her wings on my arrival, was rapidly building a nest. This was situated in the centre of the territory, about fifteen yards from the second nest of the first female. Later on in the morning I noticed the male in the presence of this second female excitedly wing-flapping, while the first female was actually sitting on the nest. Throughout the morning of May 11th the second female was occupied in building, and by May 13th she had laid the first egg. The full clutch of eggs was completed by May 19th, and on the morning of that day I found that the eggs which were on the point of hatching in the first female's second nest had been taken. On May 21st the first female was again building within a few feet of the footpath, this being her third nest, and in it was deposited one malformed egg on May 29th, and on June 9th she was building yet again, but this, her fourth nest, was never completed, although sufficiently advanced to allow of removal. The young were hatched in the second female's nest on June 1st. The behaviour of these three birds is interesting from more than one point of view. At the outset we have the curious fact of the first female building two nests, not taking into account the third and fourth ones which were the result of the second being destroyed. Why should she not have been content with the first nest? Some birds, it is true, commence one or even two nests before the final effort, but I am not aware of this habit in the case of the Willow Warbler. The position chosen for the first nest was at a considerable distance from the footpath, and the female could not, therefore, have been disturbed by passers-by. The actual situation was in a bank close to the roots of a large beech tree, where the soil was perfectly dry, and was consequently as suitable a one as could possibly be found, but it was close to
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