20 



GAME, AQUATIC, AND RAPACIOUS BIRDS. 



assistance to agriculture. Its center of abundance in North America 

 during the breeding season is west of the Mississippi River and north 

 of Iowa, east of the Rocky Mountains, but it is known to breed to 

 some extent both south and east of these limits. The marshy lakes 

 of this region afford ideal nesting sites for the species, while the 

 adjoining broad stretches of prairie land yield an abundance of their 

 favorite food. A few decades ago these birds occupied this vast 

 region undisturbed, but to-day the plow is turning up the sod and 

 the mower cutting the grass of the boundless fields over which for 

 centuries they have foraged. With the advent of agricultural oper- 

 ations some changes harmful to the birds must necessarily take place, 

 but it behooves the tillers of the soil to leave the gulls unmolested 

 as far as possible, for where they abound they are a most potent 



FIG. 8. Franklin's gull. 



factor in the reduction of insect life. They do not by any means 

 confine themselves to marshes when seeking for food, but fly over 

 the dry prairie and even visit cultivated fields, looking for grubs, 

 grasshoppers, and other insects. When unmolested they become 

 quite fearless and follow the plowman to gather the grubs and worms 

 from the newly turned furrows. 



In an investigation of the food of Franklin's gull 93 stomachs were 

 examined. Nearly all were taken from their breeding grounds and 

 in the breeding season. Unfortunately none were secured during 

 July, which is probably the very height of the reproductive period. 



Of the whole food 94.46 per cent consisted of animal matter and 

 5.54 per cent of vegetable. Of the latter nearly all was of no sig- 

 nificance, probably being taken accidentally, except the contents of 



497 



