432 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



SUPPRESSION OF VERTEBRATE PESTS. 



Birds of prey often have been known to greatly reduce the numbers 

 of injurious rodents, and in the Old World cases are recorded in 

 which birds have utterly destroyed invading armies of rodents. No 

 such striking instances have been observed in the Western Hemi- 

 sphere, although birds rendered valuable service in the Nevada 

 mouse plague of 1907-8, the only outbreak of this kind in the United 

 States, that has been scientifically studied. 40 It was estimated at the 

 time that bird predators were destroying 500,000 of the mice monthly. 



Few birds are considered pests, and fewer yet of those so consid- 

 ered have unusually efficient bird enemies. The English sparrow, 

 generally looked upon as a nuisance about buildings, but whose food 

 habits, as indicated in previous pages, have many good points, is an 

 exception, in that crows, particularly fish crows, which often nest 

 in or near southern cities, sometimes rely upon its eggs and young 

 as a steady source of food. Occasionally the activity of crows in this 

 direction results in a noticeable diminution of the number of sparrows. 



Prof. Philip R. Uhler, provost of the Peabody Institute, Balti- 

 more, says : 41 



One way, and a very peculiar way, of putting a check on the sparrows has 

 been brought to my attention. Three years ago the Peabody Institute was 

 simply swarming with sparrows. They built nests in the hollows of the balus- 

 trade on the roof, in the rain-pipe gutters on the extensions, and fluttered and 

 flew all over the place. They were laying hundreds of eggs upon the roof and 

 about and had gotten so bold as to fly down the ventilators straight into the 

 library. They were almost as thick on the top and steeple of Mount Vernon 

 Place Methodist Episcopal Church, across the street. Besides this our roof 

 was already tenanted by about 500 or more pigeons, kept by the janitor of 

 the institute and his son, who set their traps up there and fed them. One day 

 I noticed a crow on the roof of our building. I saw him look about curiously, 

 up, around, and down where the sparrows' nests were. The next thing he did 

 was to get to work on the eggs. A few days passed, and I saw him again, 

 this time accompanied by two other crows that were at the same scheme. The 

 crows from that time on increased until 12 came to that spot. 



Meanwhile there was trouble among the sparrows and the pigeons. Their 

 eggs were being eaten at an alarming rate, and they were obliged to go. And 

 go they did, so that now there is not a sparrow to be found on our roof or 

 about the institute where before there were hundreds. On the Mount Vernon 

 Place Church they have vanished in the same way, and the pigeons likewise 

 have disappeared. 



SUPPRESSION OF PLANT PESTS. 



Most pests among plants are known as weeds, and by far the ma- 

 jority of weeds depend upon seeds for their continued existence. 

 Many species of birds devour large quantities of weed seeds, but 

 this work is a specialty of the sparrow family. Where they are 



40 See Farmers' Bui. 352, pp. 21-22, and Yearbook U. S. Dept. of Agr., 1908, p. 309. 

 « Forest and Stream, 51, p. 264, 1898. 



