| OCR Text |
Show 92 Utah Academy of Sciences} Arts and Letters [Vol. XV, City, contained 6 seeds of Chenopodium sp., 2 sunflower seeds, a few pieces of corn, and 3 aquatic insect larvae. On February 4, 1934, six specimens were collected from the same locality. The stomachs of two were empty and only three contained animal matter. Analysis showed 16 seeds of Chenopodium sp., 301 of salt grass, and 21 cocklebur seeds; 4 Diptera larvae, 17 Chironomi dae, 3 ground beetles, and 4 adult and 9 larval weevils. On April 1, 1934, at Antelope Island, Davis County, a bird was taken whose stomach contained several sunflower seed-hulls, 1 unidentified seed, a few parts of a ground beetle, and 6 unidentified insect larvae. On April 10 and 11, 1934, seventeen specimens were collected along the Colorado River at a locality one mile west of Moab, Grand County. The stomachs of these contained 26 Chenopodium sp., 19 cocklebur, 424 Cleome sp., a few pieces of corn, and several unidenti fied seed-hulls; animal food consisted of 6 dipterous larvae, approximately 5 beetles (2 being Hydrophilidae), 4 caddice fly larvae (Limnophilidae), 2 damsel flies (Coenagrionidae), and 4 spiders. On April 14, 1934, a huge mixed flock of black-birds was observed feeding in an alfalfa patch which was being irrigated at the time. Eight red-wings (mostly females) were obtained. Stom ach analyses showed 1,070 aphids, 13 true bugs (Hemiptera), 1 hydrophilid beetle, 1 click beetle, pieces of 2 ground beetles, 233 weevil larvae, 12 Diptera larvae, 4 caddice fly larvae, 1 ichneumon fly, 1 chalcis fly, 2 spiders, and 28 On May 11, No vegetable matter was present. unidentified insect larvae. 1934, at Riverton, Salt Lake County, four specimens were obtained. A total of 13 large weed seeds (unidentified) and 2 beetles (1 being a ground beetle) was found in the stomachs. Summary and Conclusions Stomachs from forty-five Thick-billed Red-winged. Blackbirds, collected during the period beginning October 14, 1933 and ending April 14, 1934, were In addition, numerous field observations of feeding habits were examined. The results obtained indicated a yearly change from a winter diet, made. consisting almost entirely of weed-seeds, to a spring diet made up largely of insects. The amounts of various foods eaten apparently were correlated with the relative abundance of the same materials in the habitats concerned. Do mestic grain (corn in both cases) was found in the stomachs of only two birds, each bird having been collected from a different locality. In both cases the relative proportion of grain to total stomach contents was very small. However, it is to be noted that no birds were taken during the grain season. Most of the plant and animal materials eaten were of spgcies detrimental to agriculture and it is noteworthy that such pests as cocklebur, weevil, and The results of these studies seem to indicate that this were included. aphids bird. is beneficial to agriculture in Utah. |
