Direct Recovery Rate Research Articles

Effects of Neck Bands on Survival of Greater Snow Geese

Neck bands are a widely used marker in goose research. However, few studies have investigated a possible negative effect of this marker on survival. We tested the effect of neck bands on the survival of adult female greater snow geese (Chen caerulescens atlantica) by marking birds with either a neck band and a metal leg band or a leg band only on Bylot Island (Nunavut, formerly included in the Northwest Territories, Canada) from 1990 to 1996. Annual survival was estimated using leg-band recoveries in fall and winter and using neck-band sightings in spring and fall. Recapture rates were estimated using summer recaptures. Using recovery data, the selected model yielded a survival similar for the neck-banded and leg-banded only birds (S = 0.845 ± 0.070 vs. S = 0.811 ± 0.107). The hypothesis of equality of survival between the 2 groups was easily accepted under most constraints imposed on survival or recovery rates. However, failure to account for a different direct recovery rate for neck-banded birds would lead us to incorrectly conclude a possible negative effect of neck bands on survival. Using sighting data, mean annual survival of neck-banded birds was independently estimated at 0.833 ± 0.057, a value very similar to that estimated with band-recovery analysis. Raw recapture rates during summer were significantly lower for neck-banded birds compared to those marked with leg bands only (4.6% vs. 12.1%), but in this analysis, survival, site fidelity, reproductive status, and recapture rates were confounded. We conclude that neck bands did not affect survival of greater snow geese, but could possibly affect other demographic traits such as breeding propensity and emigration.

Direct Recovery Rates of Lesser Scaup Banded in Northwest Minnesota: Sources of Heterogeneity

Heterogeneity in direct recovery rates is an important area of study because deductions about survival rates and hunting mortality are made from recovery data. We tested the hypothesis of condition bias in hunter-killed lesser scaup (Aythija affinis) and tested differences among direct recovery rates (f= proportion of birds banded that are killed by a hunter ≤3 months after release and reported) of scaup staging on Thief Lake Wildlife Management Area (TLWMA) and Agassiz National Wildlife Refuge (ANWR) in northwestern Minnesota Scaup were trapped, held for 24 hr, weighed, banded with standard aluminum leg bands, and released during 4 October-8 November 1983-86 at TLWMA, and 1984-86 at ANWR. During 1984-86 e also sprayed areas of white plumage with fluorescent paint, colorcoded by age and location. Recovery data obtained from cooperative hunters and the U.S. Geological Survey Bird Banding Laboratory were subjectec to 3 sets of analyses. In an analysis of variance (ANOVA), after adjusting for sex, age, year, location of capture, and date of capture body mass at capture of recovered birds was lower, on average, than those not recovered Logistic regression mdicated (1) probability of recovering a bird decreased with increasing body mass; (2) within years, probability of recovery increased with date of first capture; (3) scaup at TLWMA were recovered at greater rates than scaup at ANWR: (4) hatching-year (HY) scaup were recovered at greate r rates than were after-hatcbing-year (AHY) birds; and (5) recovery was more likely during 1984-86 than in 1983. Finally, in a crude test of recovery distribution, recoveries of birds banded at ANWR were about half as likely as those banded on TLWMA to occur in Minnesota. We conclude that cohort membership (age, capture site) and condition, as measured by body mass, influence susceptibility to hunting mortalitv. These and other sources of heterogeneity in recovery rates should be considered when modeling survival of scaup.

Effect of Restrictive Harvest Regulations on Survival and Recovery Rates of American Black Ducks

Population management of waterfowl requires an understanding of the effects of changes in hunting regulations on harvest and survival rates. Mean survival and recovery rates of American black ducks (Anas rubripes) were estimated during 3 periods of increasingly restrictive harvest regulations: 1950-66, 1967-82, and 1983-93. From the first to the second period, direct recovery rates declined for at least 1 age class in 4 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 adults 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 survival rates from the second to the third period for immature males. For adults, however, survival increased less between these periods than would be expected if hunting mortality were additive and changes in recovery rates were proportional to changes in hunting mortality, Changes in survival and recovery rates of black ducks banded postseason were similar to those of adults banded preseason. Comparisons among estimates by degree blocks of latitude and longitude indicate that, at least between 1967 and 1983, estimated survival rates of immature and adult black ducks were lower in areas with high direct recovery rates. Smaller samples of banded birds and changes in banding locations in recent vears 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, suggesting the need for alternative approaches such as adaptive harvest management to increase understanding of the effects of hunting on black duck populations.

Harvesting Multiple Stocks of Ducks

This study was conducted to help assess whether recent harvest rates of ducks banded before the hunting season in the United States varied among stocks (i.e., species, age-sex cohort, location of banding) and whether regulatory actions have been successful at shifting harvest pressure among stocks in the desired manner. Direct recovery rates during 1976-91 were used to index harvest rates and were influenced to some degree by location of banding, age class, sex, species, and hunting regulations. However, differences in recovery probability among species were consistent (P = 0.787) over 3 periods with different hunting regulations (1976-84, 1985-87, 1988-91), despite regulatory changes designed to affect species differentially. Band-recovery models that excluded the interaction between hunting regulations and sex of ducks were inadequate (P ≤ 0.013), suggesting sex-specific changes in recovery probabilites with changes in regulations. There was little evidence (P ≤ 0.151) that regulatory changes affected recovery rates of ducks from 3 banding reference areas differentially. Harvesting duck stocks in an optimal manner requires an ability to harvest selectively, a good understanding of each stock's dynamics, and knowledge of any interdependence in stock sizes.

Factors Associated with Raccoon Mortality in Iowa

Biologists need to better understand the effects of harvest on the population dynamics of furbearers. Thus, we used telemetry and Cox's proportional hazards statistics to investigate how habitat factors and harvest regimes were associated with mortality patterns of raccoons (Procyon lotor) in Iowa during 1983-89. Among birth-year (BY) raccoons, greater harvest levels (as estimated by direct recovery rate of ear-tagged animals) were associated with increased hazard, or mortality rate. We found no difference in annual survival among animals >1 year old (after-birth-year, ABY), and changes in hazard rate of ABY raccoons were not associated with greater harvest levels

Effects of Radio Packages on Wild Ducks

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.