[20]From “The Relation of Sparrows to Agriculture,” by Sylvester D. Judd, Bulletin No. 15, Biological Survey.
[21]From “Useful Birds and Their Protection,” by E. H. Forbush.
[22]Bulletin No. 15, U. S. Dept. of Agriculture, Biological Survey.
[23]“Useful Birds and Their Protection,” E. H. Forbush, page 328.
[24]Bulletin No. 21, Bureau of Biological Survey, U.S. Department of Agriculture.
[25]From “Useful Birds and Their Protection,” by E. H. Forbush.
[26]From “Useful Birds and Their Protection,” by E. H. Forbush.
[27]“Useful Birds and Their Protection, ” by E. H. Forbush, page 210.
[28]Farmers’ Bulletin 630, Biological Survey, U. S. Department of Agriculture.
[29]Educational Leaflet No. 61, National Association of Audubon Societies.