EFFECT OF RESTRICTIVE HARVEST REGULATIONS ON SURVIVAL AND RECOVERY RATES OF AMERICAN BLACK DUCKS

Population management of waterfowl requires an understanding of the ef fects of changes in hunting regulations on harvest and survival rates. Mean survival and recovery rates of American black ducks (Anas rubrip es) were estimated during 3 periods of increasingly restrictive harves t regulations: 1950-66, 1967-82, and 1983-93. From the first to the se cond period, direct recovery rates declined for at least 1 age class i n 3 of 6 reference areas, with a mean decline of 14% for adult and 7% for immature black ducks. From the second to the third period, direct recovery rates declined in all areas, declines averaging 37% for adult s and 27% for immatures. Estimated mean survival rates increased from the first to the second period, consistent with a model of additivity of hunting mortality. Limited evidence existed for increases in surviv al rates from the second to the third period for immature males. For a dults, however, survival increased less between these periods than wou ld be expected if hunting mortality were additive and changes in recov ery rates were proportional to changes in hunting mortality. Changes i n survival and recovery rates of block ducks banded postseason were si milar to those of adults banded preseason. Comparisons among estimates by degree;blocks of latitude and longitude indicate that at least bet ween 1967 and 1983, estimated survival rates of immature and adult bla ck ducks were lower in areas with high direct recovery rates. Smaller samples of banded birds and changes in banding locations in recent yea rs may be limiting ability to evaluate consequences of recent changes in harvest rates. These correlation-based studies are limited in their ability to explain causes of observed changes in survival rates, sugg esting the need for alternative approaches such as adaptive harvest ma nagement to increase understanding of the effects of hunting on black duck populations.