. Birds in their relations to man; a manual of economic ornithology for the United States and Canada . rus. Nearly half of the foodof several house-wrensconsisted of canker-worms. Passing now to thewarblers (Mniotiltidce),we conic to many spe-cies feeding largely oncanker-worms. Four-fifths of the food of asingle Tennessee war-bler consisted of theseinsects. Two-thirdsof that of five sum-mer yellow-birds wascanker-worms, andthe same was true oftwo chestnut-sidedwarblers and also offour black-poll war-blers. A single black-throated green war-bler had eaten seventy per cent, of canker-worms, and
. Birds in their relations to man; a manual of economic ornithology for the United States and Canada . rus. Nearly half of the foodof several house-wrensconsisted of canker-worms. Passing now to thewarblers (Mniotiltidce),we conic to many spe-cies feeding largely oncanker-worms. Four-fifths of the food of asingle Tennessee war-bler consisted of theseinsects. Two-thirdsof that of five sum-mer yellow-birds wascanker-worms, andthe same was true oftwo chestnut-sidedwarblers and also offour black-poll war-blers. A single black-throated green war-bler had eaten seventy per cent, of canker-worms, and twoMaryland yellow-throats had eaten forty per cent, of theseand forty per cent, of other caterpillars. Consequently canker-worms composed nearly or quite two-thirds of the food ofthese fifteen warblers. Seventy-nine per cent, of the foodof three warbling vireos consisted of caterpillars, more thanhalf of them being canker-worms. Out of a flock of about thirty cherry-birds, or cedar wax-wings, seven birds were shot. With the exception of a fewAphodii (small beetles) eaten by three of the birds in. THE BLUEBIRD. BIRDS AS REGULATORS OF OUTBREAKS. 71 numbers too insignificant to figure in the ratios, the entirefood of all these birds consisted of canker-worms, whichtherefore stand at an average of one hundred per cent. Thenumber in each stomach determined by actual count rangedfrom seventy to one hundred and one, and was usually nearlyone hundred. Assuming that these constituted a whole daysfood, the thirty birds were destroying three thousand wormsa day, or ninety thousand for the month during which thecaterpillar is exposed. A specimen each of the cliff-swallow, American gold-finch, and yellow-winged sparrow had eaten no one-third of the food of eight chipping-sparrows con-sisted of caterpillars, half of them being field-sparrows had eaten largely of canker-worms andvarious beetles, forty-three per cent, of the food of fourteenblack-throate
Size: 1276px × 1959px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectbirds, bookyear1903
