BIRDS AND INSECTS 171 



should take some steps to encourage the birds that 

 had been observed to feed upon the larvse of the saw- 

 fly. 



The principal birds that were thus observed to be 

 holding the insect in check were the robins, tits, and 

 the fly-catchers. All these birds build their concealed 

 nests in holes in the trees, and, as the trees of the 

 district are mainly conifers, the supply of hiding- 

 places was necessarily limited. It was therefore 

 decided to put up a number of properly-constructed 

 nesting-boxes in the neighbourhood of the larch plan- 

 tations that were most severely attacked, and to feed 

 the birds in the winter on protected feeding-platforms. 

 This was done. Boxes of two sizes were suspended 

 in the trees, and the number of boxes was increased 

 year by year. At the end of the first summer the 

 boxes were examined, and it was found that about 

 30 per cent had been occupied during the nesting 

 season. This was considered to be a satisfactory 

 result, considering the bird population of that beauti- 

 ful but at the same time rather inhospitable district. 

 But in the following year the percentage of boxes 

 occupied increased, and the same in succeeding years, 

 until in 1912 no less than 71 per cent of them con- 

 tained one or more nests. 



The result of these efforts was a noticeable increase 

 in the number of birds in the district, and every year 

 they waged a more intense warfare on the saw-fly. 

 I do not think that there can be any reasonable doubt 

 that as a direct result of these encouragements the num- 

 ber of tits, robins, starlings, and some other species 

 of birds in the Thirlmere plantations was considerably 

 increased. On this point our own observations were 

 fully confirmed by the opinions of people living in 

 the district who were well acquainted with the bird 

 life before and after the boxes were provided, but the 



