THE EFFECTS OF ORNITROL ON WILD POPULATIONS OF RED-WINGED BLACKBIRDS AND GRACKLES

For the past three years the New Jersey Department of Agriculture, in coop¬eration with the New Jersey Agricultural Experiment Station, has conducted field evaluations on the effects of reproductive suppressants on wild populations of red-winged blackbirds. These studies have been performed in conjunction with the North East 49 (a Federally sponsored regional project which presently has nine states in the North East and Ohio cooperating to develop means to combat bird damage to agricultural crops) regional project on control of bird depredations. Field evaluations in 1968 and 1969 centered around the effects of TEM (tri-ethylene melamine) on the reproductive rates of red-winged blackbirds. At the close of the 1969 season further field testing of the chemical was discontinued because of the material's apparent lack of effectiveness as a reproductive inhibitor. In 1970 the field evaluations were conducted to determine the effects of Orni-trol (20, 25-diazocholesterol dihydrochloride, supplied by G. D. Searle and Company, Chicago, Illinois) on the reproductive rates of red-winged blackbirds. A small colony of common grackles was also studied during this same investigation.

Overabundant deer: Better management through research

Overabundance of white-tailed deer (Odocoileus virginianus) continues to challenge wildlife professionals nationwide, especially in urban settings. Moreover, wildlife managers often lack general site-specific information on deer movements, survival, and reproduction that are critical for management planning. We conducted radio-telemetry research concurrent with deer culling in forest preserves in northeastern Illinois and used empirical data to construct predictive population models. We culled 2,826 deer from 16 forest preserves in DuPage County (1992-1999) including 1,736 from the 10 km2 Waterfall Glen Forest Preserve. We also radio-marked 129 deer from 8 preserves in DuPage and adjacent Cook County (1994-1998). Recruitment was inversely associated with deer density suggesting a classic density-dependent response. Female deer were philopatric and 20% of adult males dispersed. Survival was high for all sex and age classes, and deer-vehicle collisions accounted for >55% of known mortalities. Based upon data from other areas, early attempts to apply population models to deer at Waterfall Glen Forest Preserve were not useful. The subsequent quantification of the density-dependent recruitment response and use of other empirical data strengthened the predictive capability of models. Our experience illustrates the importance of understanding demographics of overabundant deer in order to set realistic objectives and make sound management decisions.