Bird Notes and News 



11 



Economic Ornithology 



BIRDS, INSECTS, AND CROPS 



Two interesting addresses, the one dealing 

 with the value of wild birds as insect destroyers, 

 and the other with the ravages of insect enemies, 

 were given on March 3rd, 1922. 



Lecturing at the Royal Institution, London, 

 Professor Maxwell Lefroy gave a lurid account 

 of the " exploitation " of mankind by insect 

 pests. The flea he accused (according to the 

 newspapers) of carrying bubonic plague, and 

 the Argentine ant of eating a baby as well as 

 virtually killing off bird life in the Island of 

 Madeira. On economic grounds, he illustrated 

 the ravages of insect pests among the crops— 

 the boll weevil in the cotton crops of America, 

 the Colorado beetle among the potatoes, and 

 the corn borer and green weevil in the world's 

 wheat crop. Between 1914 and 1921, he said, 

 the American cotton crop diminished from 

 14,000,000 bales to 7,000,000 bales, almost 

 entirely through the ravages of the weevil. 

 The grain weevil, again, had very seriously 

 affected our food supplies during the war. 

 It attacked the grain stored in Australia for 

 shipment to this country, and over £450,000 

 had to be spent on machinery to save the 

 wheat. 



At York Museum, Dr. W. E. Collinge lectured 

 on the insect-food of wild birds in relation to 

 food production. The majority of our wild 

 birds, he observed, were beneficial, and only a 

 very few species injurious, and these latter 

 might be controlled and their injuries materially 

 lessened by proper repressive measures. It was 

 dif&cult to estimate the enormous bulk of food 

 that a bird consumed, but a bird about the size 

 of a Skylark consumed about six pounds of food 

 per year, so that 10,000 birds would require 

 about 27 tons, of which fully half or more 

 consisted of insects and caterpillars. Taking 

 ten Skylarks and examining their stomach 

 contents, it was found that the average number 

 of insects, etc., consumed in an ounce was 162, 

 so that 10,000 birds would consume nearly 

 80,000,000 insects in a year. From carefiil 

 investigation at different periods of the day 

 it was found that each Song-Thrush consumed 

 approximately on an average something like 

 336 insects and caterpillars per day, or 10,000 

 per month. In the nesting season many more 

 would be consumed, so it would not be over 



estimating the figure to say that during April, 

 May, and June each bird accounted for the 

 destruction of upwards of 30,000 insects, most 

 of which were injurious to the farmer and fruit 

 grower. Assuming there were 100,000 Song- 

 Thrushes in the British Isles, these birds would 

 in the three months mentioned account for the 

 destruction of 3,024,000,000 insects. The whole 

 of this material would weigh over 500 tons, 

 and would be capable of destroying in 14 days 

 10,000 tons of produce, or £50,000 worth of 

 home-grown food. " This is but a single 

 instance," said Dr. Collinge ; " what the cumu- 

 lative effect must be of 50 or 60 species feeding 

 upon insects and caterpillars for the greater 

 part of the year, we are unable to estimate, but 

 this at least we can state, that they must 

 exercise a control such as few realise, and 

 without which it would be almost impossible 

 to cultivate the land to any profitable purpose. 

 Once the people of this country realise what a 

 potent factor wild birds are in the protection 

 of our food crops and our forests, then more 

 enlightened views will prevail, the tardy 

 machinery of the State will be forced to move 

 more quickly and more effectively, in order to 

 preserve and protect a natural force of inestim- 

 able value to mankind." 



THE HOUSE-SPARROW AND THE PEAS 



Canon Theodore Wood, writing in the 

 Morning Post (February 4th, 1922), points out 

 that the Sparrow, with all its sins, " accused of 

 almost every crime a bird can commit," is not 

 wholly bad. It has at least one counter- 

 balancing virtue to redeem its thousand crimes ; 

 for in the nesting season it is insectivorous. 

 " I do not merely mean that it feeds its young 

 with grubs. I mean that it lives itself partly 

 on highly injurious insects. At one time I 

 made rather a speciality of growing peas. I 

 found, one spring, that the leaves of the young 

 plants, just at the most critical stage of their 

 growth, were badly chipped, and in some cases 

 destroyed altogether. The gardener attributed 

 the mischief to the Sparrows, which were con- 

 stantly at work among the rows. So I caught 

 half a dozen, and examined the contents of their 

 crops. In one case there was nothing at all. 

 The bird had evidently just arrived when I 

 caught it, and had not begun its meal. In the 

 other five I found no vestige of pea-leaves at 

 all. What I did find, in each, was a mass of the 



