June 30, 1899.] 



SCIENCE. 



905 



level. It is a continual repetition of taking 

 a step too many at the top of tlie stairs. 



The most strongly marked characteristics 

 of the whole experience lay in the change 

 wrought in the affective overtone of per- 

 ceptual objects in the suggestion of new 

 touch-qualities and impulses, and the exist- 

 ence of abnormal emotional attitudes, but 

 these matters lie too far afield to be con- 

 sidered in the present paper. 



EOBEET MacDoUGALL. 



Haevaed Univeesity. 



BIRDS AS WEED DESTROYERS.* 

 A MILLION weeds can spring up on a sin- 

 gle acre. Cultivation will do much to 

 eradicate these noxious plants, but some 

 will always succeed in ripening a multitude 

 of seeds to sprout the following season, so 

 as to make tilling the soil an everlasting 

 war against weeds. Certain garden weeds 

 produce an incredible number of seeds. 

 Thus a single plant of purslane may mature 

 a hundred thousand seeds in the fall, and 

 if unchecked would produce in the spring 

 of the third year ten billion plants. 



Probably the most efficient check upon 

 this unbounded increase of seeds is to be 

 found in the seed-eating birds which flock 

 by mj'riads to agricultural districts to feed 

 upon the bounty of the weed-seed harvest 

 from early autumn until lale spring. Since 

 birds attack weeds in the most critical stage 

 of the plant cycle, it follows that their ser- 

 vices will be of actual practical value. The 

 benefits are greatest in case of hoed crops, 

 since here found the largest number of an- 

 nual weeds, which, of course, are killed by 

 frost and must depend for perpetuation 

 solely upon their seeds. Seed-eating species 

 of birds prevent, in a large measure, weeds 

 of this class, such as, for instance, ragweed, 

 chick weed, purslane, crab grass, pigweed, 



* Birds as Weed Destroyers. Year-book of De- 

 partment of Agriculture for 1898, pp. 221-232 in- 

 clusive. 



lamb's quarters and several weeds of the 

 genus Polygonum, from seeding down the 

 land with a rank vegetation fatal to culti- 

 vated crops. The problem of weed destruc- 

 tion is of such magnitude that Mr. F. V. 

 Coville, Botanist of the United States De- 

 partment of Agriculture, in discussing weed 

 legislation, has said, * * * " Since the 

 total value of our principal field crops for 

 the year 1893 was $1,760,489,273, an in- 

 crease of only 1 per cent., which might 

 easily have been brought about through the 

 destruction of weeds, would have meant a, 

 saving to the farmers of the nation of $17,- 

 000,000 during that year alone." 



The birds most actively engaged in con- 

 suming weed seed are horned larks, black- 

 birds, cowbirds, meadow larks, doves, quail, 

 finches and sparrows. In a field sparrow's- 

 stomach I found 100 seeds of crab grass, in 

 a snowflake's stomach 1,000 seeds of pig- 

 weed, and in a mourning dove's crop 7,500 

 seeds of Oxalis stricta. That the destruction 

 of weed seed by birds is extensive enough 

 to be of considerable benefit to the farmer 

 is shown by Professor F. E. L. Beal, who 

 estimated that in the State of Iowa alone a 

 single species, the tree sparrow, consumes 

 annually 875 tons of weed seed. 



From the examination of the stomachs of 

 some 4,000 bii'ds it has been determined that 

 the best weed destroyers are the goldfinches, 

 grosbeaks and a dozen species of native 

 sparrows. 



In cities the English sparrow, assisted by 

 several native species, does good work by 

 feeding upon the seeds of lawn weeds, such 

 as crab grass, pigeon grass, chickweed and 

 the dandelion. On the lawns of the De- 

 partment of Agriculture, in Washington, the 

 birds feed upon dandelions from the middle 

 of March until the middle of August. Af- 

 ter the yellow petal-like corollas have dis- 

 appeared, and the flower presents an 

 elongated egg-shaped body, with a downy 

 tuft at the upper end, the sparrow re- 



