Estimated Effectiveness of a Waterfowl Nontoxic Shot Zone

Abstract

Examination of gizzards from 934 mallards (Anas platyrhynchos) collected at three eastern Kansas marshes disclosed a 7.6% incidence of ingested shot. A differential incidence of lead and steel shot in gizzards of mallards from areas with and without lead shot restrictions allowed an evaluation of the effectiveness of a nontoxic shot zone. Nontoxic shot regulations on one marsh area appeared responsible for reducing by 48% the annual loss of mallards to lead poisoning. Nontoxic shot zones have been established in many parts of the United States in an effort to reduce lead poisoning losses in waterfowl populations. Although this regulatory practice may reduce the deposition of additional lead shot in specific areas, the transitional effectiveness of nontoxic zones in reducing waterfowl losses has not been determined. This paper presents results of a 1982-1985 study that addresses this issue. STUDY AREAS AND METHODS This study was conducted in eastern Kansas, on the 2894-ha Marais des Cygnes Wildlife Management Area (MDCWMA) and two duck hunting clubs within 5 km of MDCWMA, the 300-ha Patterson Duck Club (PDC) and the 120-ha Boicourt Shooting Club (BSC). Specific locations and descriptions are in Furness (1986). Use of nontoxic shot has been required on MDCWMA since 1980, but not on the clubs. Mallards (Anas platyrhynchos) are the most numerous duck on MDCWMA during fall, with an average mean peak of 51,000 during December 1980-1985 (R. A. Warhurst, unpubl. reps.). No comparable estimates for mallard populations are available for BSC or PDC. Gizzards were collected from 934 mallards killed by hunters on the three study sites throughout the hunting seasons; 754 from MDCWMA, 72 from BSC, and 108 from PDC. Gizzards were stored frozen, then later thawed ' Present address: Comparative Toxicology Laboratories, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506. This content downloaded from 157.55.39.225 on Wed, 28 Sep 2016 06:02:00 UTC All use subject to http://about.jstor.org/terms 144 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE Table 1. Number of ingested shot in gizzards of mallards harvested on three study sites, 1982-1985. Gizzards Number of shot per gizzard Site N With shot 1 2 3 4 5 6 >6 MDCWMA 754 54 (7.2)a 38 (70.4) 10 (18.5) 0 (0.0) 2 (3.7) 0 (0.0) 1 (1.8) 3 (5.6) Boicourt 72 5 (6.9) 5 (100.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) Patterson 108 12(11.1) 9 (75.0) 2(16.7) 1 (8.3) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) Totals 934 71 (7.6) 52 (73.2) 12 (16.9) 1 (1.4) 2 (2.8) 0 (0.0) 1 (1.4) 3 (4.2) a Percentages in parentheses. and opened under a gentle flow of water.