EFFECTS OF TWO GRASSHOPPER CONTROL INSECTICIDES ON FOOD RESOURCES AND REPROUCTIVE SUCCESS OF TWO SPECIES OF GRASSLAND SONGBIRDS

摘要

We conducted a field experiment to determine the direct and indirect effects of spraying two broad-spectrum insecticides with widely differing avian toxicities in grassland habitat on the survival and reproductive success of nesting songbirds. Three 56- ha plots were sprayed with Decis 5F~TM, three plots were sprayed with Furadan 480F~TM, and three plots were left unsprayed. Insecticides were applied at rates recommended for grasshopper control. Grasshopper(Orthoptera: Acrididae)density was measured throughout the spring and summer. Nests of chestnut-collared longspurs(Calcarius ornatus)were monitored to determine survival rates and nestling growth.