A Comparison of Capture-Recapture with Capture-Removal for Quail Populations

Abstract

The effects of paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride) on reproduction and growth of northern bobwhite (Colinus virginianus) were studied. In the parent generation (P) paraquat was administered at 0, 20, 60, and 180 ppm for 6 weeks. Reproductive variables examined included egg production, fertility, hatchability, chick abnormalities, and chick survival and weights to 7 days of age. Untreated breeders in the second generation (F1) phase were the offspring of the various groups in the first generation phase. Reproductive variables examined included egg production, number of days to first and last egg of a 20-egg clutch, fertility, and hatchability. P hens fed 180 ppm laid fewer eggs (all differences are at P < 0.05) during treatment compared to their pre-treatment period and to controls, and had lower ovary and oviduct weights. There were no differences in P fertility nor in chick abnormalities or survival as compared to controls. Chicks from P parents fed 20 ppm paraquat were heavier than all other treatments. P male and female post-treatment weight did not differ from pre-treatment weight. F, hens from paraquat-treated parents started laying 1 week later than controls and produced eggs at a lower rate resulting in clutch completion 10 days later than controls. There were no differences in F, fertility, hatch, or relative testes, ovary, and oviduct weights. Adult F, hens from parents fed 60 and 180 ppm paraquat weighed less. J. WILDL. MANAGE. 49(4):1066-1073 Paraquat is used extensively throughout the world for the control of weeds in orchards and crop fields and as a crop desiccant. Increased use of paraquat has resulted from an increase in no-tillage agriculture. Paraquat is available in the United States primarily as paraquat dichloride, a 29.1% liquid concentrate containing 0.9 kg paraquat cation/3.8 liter. The recommended field application rate usually ranges from 0.28 to 1.12 kg paraquat cation/ha (Ortho Tech. Inf., Chevron Chem. Co., Richmond, Calif., 1974). Residues of about 30 ppm in alfalfa and 60 ppm in adventitious graminaceae have been found after paraquat treatment at a r commended field level (De Lavaur et al. 1973). Paraquat residues have been reported to be as high as 1,000 ppm in herbage on grazing plots treated with the highest recommended application level (Calderbank et al. 1968). Some wildlife species may be affected by recommended field application rates of paraquat (Ernest 1971, De Lavaur et al. 1973, Dial and Bauer 1984). De Lavaur et al. (1973) found that 50% of hares (Lepus europaeus) exposed to alThis content downloaded from 157.55.39.83 on Sun, 09 Oct 2016 05:00:36 UTC All use subject to http://about.jstor.org/terms