68 The N.Z. Journal of Science and Technology. ' [Mar. 
of grit and soil is taken into the intestinal canal. Thus observations made 
upon the grit and soil contents in the gizzards of thirty-six rooks during 
the dry summer of 1911 (June to September) showed that the average 
content was 108 grains, of which not more than one-sizth was grit, whereas 
in the same number of birds examined during the wet summer of 1912 
the average amount was 214 grains, of which nearly one-third was grit. 
Similar investigations carried out on the starling and house-sparrow gave 
an average in 1911 of 42 and 27J grains respectively, as against 68 and 
53 grains in 1912. 
In the past it has been all too readily assumed that those species that 
feed upon insects and upon weed-seeds must be beneficial. We now know 
that no hard-and-fast line can be drawn : much careful and extended work 
is necessary on each individual species before it can be definitely stated 
that a species is injurious or beneficial. 
To the farmer and fruitgrower such information is of the greatest 
import, for at the present moment they suffer enormous annual losses 
due to certain species of birds. 
Of the majority of species of British wild birds it is generally agreed 
that they are beneficial; of the remainder the present writer has elsewhere 
stated that “ Many species which are injurious at one season of the year 
are distinctly beneficial for the remainder. Again, many birds that are 
beneficial may, if allowed unduly to increase, become equally injurious. 
In other cases the partial failure of their natural food-supply, or other 
causes, may lead to a change in their food habits ; in a like manner the 
alteration or removal of their natural environment may lead to equally 
disastrous results.” 
Although in some districts farmers and others are loud in their com¬ 
plaints of the injuries inflicted, any policy of wholesale destruction would, 
we believe, be equally disastrous. In nearly all cases “ the misdeeds of 
birds are much more manifest than the benefits they confer upon us.” 
With the exception of doves and pigeons, practically all birds feed 
their young upon an animal diet, whatever the nature of the food of the 
adult may be, and the bulk of the food consists of insects. These are 
destroyed just when they are capable of inflicting the greatest possible 
harm upon our crops and orchards. Further, during the nestling season 
the young birds require an enormous amount of food ; feeding commences 
before sunrise and continues after sunset. The starling is known to pay 
nearly two hundred visits to the nest a day, and in the case of the house- 
sparrow between 220 and 260 visits daily have been counted. In any 
attempt, therefore, to estimate the value or economic status of a species 
the nature of the food of the nestlings must be taken into consideration. 
A careful investigation extending over a period of ten years, entailing 
an examination of the stomach-contents of upwards of four thousand adult 
birds and six thousand nestlings, and numerous observations in the field 
laboratory, shows that we can classify the commoner species under five 
headings, viz. :— 7 
1. Distinctly injurious : House-sparrow, bullfinch, sparrow-hawk, 
wood-pigeon, and stock-dove. 
2. Too plentiful, and consequently injurious : Missel-thrush, black¬ 
bird, greenfinch, chaffinch, starling, and rook. 
3. Injurious, but not plentiful: Blackcap. 
4. Neutral : Jay. 
5. Beneficial: Song-thrush, fieldfare, white-throat, great tit, blue 
tit, wren, goldfinch, linnet, yellow bunting, magpie, jackdaw, 
skylark, barn-owl, brown owl, kestrel, and plover. 
