Effects of Radio Packages on Wild Ducks

Abstract

A total of 211 wild, free-flying mallards (Anas platyrhynchos) and wood ducks (Aix sponsa) were equipped with breast-mounted radio packages during the breeding seasons of 1968-72. Known predation loss was 7.6 and 12.0 percent for mallards and wood ducks, respectively; 60 percent occurred within 3 weeks of instrumentation. The highest predation rate for mallards was 0.0048 kills per tracking day and 0.0136 for wood ducks. A higher direct recovery rate for instrumented birds (19.5 percent) than noninstrumented birds (8.1 percent) was probably due to the novelty of the transmitter to hunters. Departure patterns and locations of direct recoveries were similar between radio-equipped and normalbanded birds. Among female wood ducks with radios, recovery rates were lower than expected. Hunters indicated that 84 percent of the instrumented ducks recovered were in good or excellent condition. Recaptures of ducks as long as 1 year after being equipped with radio packages indicated that feather wear and skin abrasion were not serious. A high rate for feeding on land by instrumented mallards was probably due to our ability to more easily locate and observe these birds in cover. Preening rates were higher for instrumented ducks. As the birds became adjusted to the package, preening decreased and feeding on water increased. Social and breeding behavior of instrumented ducks did not appear to be adversely affected by the radio package. J. WILDL. MANAGE. 38(2):243-252 Radiotracking techniques are widely used in wildlife studies (Schladweiler and Ball 1968, Will and Patric 1972); however, the effects of radio packages (transmitter, battery, and harness) on behavior and survival of marked animals are poorly understood. It is difficult to make comparisons with controls because the same factors that dictate the use of telemetry often preclude gathering data on unmarked animals. Several studies have been undertaken to evaluate the effects of radio packages on the behavior and physical condition of instrumented birds. Johnson (1971) legbanded and released 785, 11-week-old male ring-necked pheasants (Phasianus colchicus); 393 were equipped with radiopackages in which transmitter and battery were simulated. He concluded from reported recoveries and bag checks that the radio packages did not affect the survival, dispersal, or growth rates of marked birds. Boag (1972) evaluated effects of radio packages on the behavior of 13 male and 7 female pen-reared captive red grouse (Lagopus 1. scoticus). He reported that food consumption of females was significantly reduced during the first 6 days after attachment of radio packages and that activity levels were reduced in both sexes for approximately 2 weeks. Habitat choice did not differ between radio-equipped and unmarked grouse. Greenwood and Sargeant (1973) measured the effect of back-mounted radio packages on the physical condition of 60 pen-reared captive mallards and bluewinged teals (Anas discors). Birds equipped with radio packages lost more weight than did controls. Feather wear and skin irritation occurred on nearly all marked individuals. Periodic observations suggested that treated birds preened more than control birds and exhibited a partial aversion to swimming. 'Present address: U.S. Bureau of Sport Fisheries and Wildlife, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401. J. Wildl. Manage. 38 (2):1974 243 This content downloaded from 157.55.39.153 on Mon, 19 Sep 2016 05:05:33 UTC All use subject to http://about.jstor.org/terms 244 EFFECTS OF RADIOS ON WILD DUCKS * Gilmer et al. Table 1. Adult mallards and wood ducks radio-equipped on the Chippewa National Forest study area in north-central Minnesota, 1968-72.