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Show Utah Academy of Sciences, Arts and Letters 136 [Vol. XIV, During 1935 and 1936, insectivorous birds were collected throughout Utah whenever opportunity afforded, to see if the taking of beet leafhoppers was common in areas not containing high beet leafhopper populations, The totals given in Table 10 list twenty-two bird species which contained tenellus, and a total of 2570 recognizable beet leafhoppers in all stomachs examined, when the 1935 and 1936 figures are added to those of (24) the 1934 study. Thus, it seems that insectivorous birds perform their most conspicuous service dur ing the fall migration, when large flocks of insectivorous birds descend upon heavily infested beet leafhopper breeding areas, thus reducing fall populations. Density of leafhopper population, number of the important bird species, and duration of their stay upon the breeding grounds, were important factors in the effectiveness of birds in the reduction of this pest. Western chipping sparrow, rock wren, Shufeldt junco, Gambel's sparrow, Audubon warbler, American pipit, pileated warbler, western vesper and Brew er's sparrow appeared to commonly ingest tenellus. A total of 22 bird species contained beet leafhoppers in their· stomachs. Undoubtedly many other bird species also ingest beet leafhoppers, when they may be captured conveniently. Table 10. A Summary of the Total found in bird stomachs. No. birds collected Birds Desert Horned Lark American Barn Swallow Rock Wren Sage Thrasher Mountain Bluebird " " " " " " " " Ashy Ruby-Crowned Kinglet American Pipit White-Rumped Shrike , Rocky Mt. OrangeCrowned Warbler Western Yellow Warbler Audubon Warbler Townsend Warbler Pileolated Warbler Nevada Savannah Sparrow Brewer's Western I'I " " " " " " " " Sparrow,',' Vesper " Sparrow " Sage Sparrow Shufeldt Junco " Clay Colored Sparrow II Western Chipping " IS parrow Gambel's Sparrow Lincoln Sparrow Totals " II " 'I' 49 19 48 12 124 4 77 12 10 2 49 3 14 8 1 19 15 2S 1 140 7S Number of No. No. E. tenellus contained containing 11----,-------.,.-- Adults E. tenellus II II I I 6 " 1 I' 16 1 2 ,II 2 'I I, I I I, 16 II " " " II I II 6 I 713 " 1 3 2 10 1 8 2 1 7 3 12 1 83 13 4 19S Eutettix 235, 245 1 o I 1 I " 2 'I I, 26 I' I I, I I I I Nymphs I Tota_l 10' 73 " tenellus 2 4 13: 12 1 3 68 4 5 4 9 2 22 8 43 o 31 4 24 67 5 S o 21 5 26 16 4 214 64 167 o 230 68 180 2 22 1047 74 13 2 42' 2 53 12 /'I , 203 15 20 1250 96 35 " 484 2086 2570 |
