Distribution of female northern pintails in relation to hunting and location of hunted and non-hunted habitats in the Grassland Ecological Area, California

To provide baseline information and better understand distribution of northern pintails (Anas acuta) in relation to hunting and distribution of hunted and non-hunted habitats in the Grassland Ecological Area (EA), we radio-tagged 191 Hatch-Year(HY) and 228 After-Hatch-Year (AHY) female pintails in the San Joaquin Valley and tracked their movements in the Grassland EA during September-March 1991-94. We investigated how the relative importance of public (National Wildlife Refuges [NWRs], California Department of Fish and Game Wildlife Areas [WAs])vs. private areas (e.g., waterfowl hunting clubs [Clubs]), use of individual areas, and night destinations from specific day-use areas varied with in and among winters and with pintail age and capture location. Overall, 64% of day and 85% of night pintail locations in the Grassland EA were on private areas. Day use of private areas was greater during nonhunting weeks (73% of all locations) and nonshoot days of hunting weeks (62% of all locations) than during shoot days (17% of all locations), when most pintails used public area sanctuaries. The effect of hunting lingered but faded, with use of private areas I day after hunting slightly less than 2 days after hunting (57% vs. 66%). Use of private areas on nights during nonhunting weeks and after nonshoot days of hunting weeks was identical (86%). Night use after shoot days was lower (79%), although the difference was significant only during the opening week of hunting. AHY females stayed on sanctuaries at a higher rate at dusk on shoot days and used the East Grassland (EGL) more than HY females. Use of private areas during the hunting season declined in 1993-94, possibly because newly-restored public area habitats attracted pintails. Night use of private areas during nonhunting weeks was lowest during 1991-92, the year drought prevented summer irrigations, and probably reduced food production on most private but few public wetlands. San Luis NWR was the most important shoot day sanctuary but Kesterson NWR use increased after wetlands in its sanctuary were restored. Merced NWR was the only public area receiving high use at night during the hunting season. Most pintails that left Merced NWR at night flew to South Clubs rather than to closer East or North Clubs. Few pintails from Kesterson NWR flew to South Clubs at night but San Luis NWR and Los Banos WA pintails used both North and South Clubs at night. The percentage of San Luis NWR pintails going to South Clubs increased after the first hunting interval, except in 1993, when 10% instead went to newly restored Salt Slough WA watergrass (Echinochloa crusgalli) marsh. Pintails were more likely to use areas during hunting season that they frequented during August October before hunting began, indicating that early habitat conditions influenced pintail use later in winter. Pintail distribution changed among intervals and years in response to changing hunting pressure and distribution of hunted and nonhunted habitats. Our data can serve as a baseline to evaluate response of pintails to changes in habitat management in the Grassland EA.