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An Evaluation of June Wood Duck Banding in the Southern Atlantic Flyway
Gregory D. Balkcom, Pamela R. Garrettson, and R. Joseph Benedict, Jr.

Southeastern Naturalist, Volume 13, Issue 3 (2014): 600–606

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Southeastern Naturalist G.D. Balkcom, P.R. Garrettson, and R.J. Benedict, Jr. 2014 Vol. 13, No. 3 600 2014 SOUTHEASTERN NATURALIST 13(3):600–606 An Evaluation of June Wood Duck Banding in the Southern Atlantic Flyway Gregory D. Balkcom1,*, Pamela R. Garrettson2, and R. Joseph Benedict, Jr.3,4 Abstract - In waterfowl banding studies, the preseason banding period is commonly accepted as July through September; however, in an effort to increase Aix sponsa (Wood Duck) banding in the Atlantic Flyway, several state agency biologists have considered banding Wood Ducks in June. We analyzed existing Wood Duck banding data to determine if direct band-recovery rates of Wood Ducks banded in June differed from those banded during July–September. We calculated direct recovery rates by state, month, and year for 1998–2007 at selected states in the Atlantic Flyway. Arcsine-transformed direct bandrecovery rates differed by month of banding (P = 0.0099; F = 3.973; df = 3, 111) and were lower in June than in July or August. We suggest that state or federal agencies conducting Wood Duck banding should spend their time and effort during the traditional banding period 1 July–30 September. Introduction There are 3 main assumptions in basic mark-recapture studies: (1) the population is closed to additions and losses during the project, (2) marks are not lost or overlooked, and (3) all individuals in the population are equally likely to be captured in each sample (Skalski and Robson 1992, Williams et al. 2002). To meet assumptions 1 and 2, researchers often try to mark animals so that the time period between sampling occasions is relatively brief (e.g., days or weeks; Williams et al. 2002). However in reality, the marking period often extends over months in order to capture a large enough sample size to produce statistically valid results. Banding is an important tool for waterfowl management, and results are often used to help establish harvest regulations (Nichols et al. 2007). Establishing waterfowl hunting regulations in the US involves cooperation by the US Fish and Wildlife Service (federal government) and the Flyway Councils that represent the state governments (Blohm et al. 2006). The Atlantic Flyway Council is a coalition of states, provinces, and territories that works in conjunction with the respective federal governments to manage migratory birds and their habitats in eastern North America and along the Atlantic coast. Harvest regulations for many waterfowl species are set using a process that includes estimates of annual survival rates and harvest rates that are derived from banding and recovery data (Nichols et al. 1Georgia Department of Natural Resources, Wildlife Resources Division, Game Management Section, Fort Valley, GA 31030. 2US Fish and Wildlife Service, Division of Migratory Bird Management, Laurel, MD 20708. 3Florida Fish and Wildlife Conservation Commission, Division of Hunting and Game Management, Tallahassee, FL 32311. 4Current address - Tennessee Wildlife Resources Agency, Division of Wildlife and Forestry, Nashville, TN 37204. *Corresponding author - greg.balkcom@dnr.state.ga.us. Manuscript Editor: Michael Steinberg Southeastern Naturalist 601 G.D. Balkcom, P.R. Garrettson, and R.J. Benedict, Jr. 2014 Vol. 13, No. 3 1995, Williams and Johnson 1995). In waterfowl banding studies, the pre-hunting season (hereafter preseason) banding period is commonly accepted as July– September (Nichols 1991, Nichols et al. 1983). This period begins when most ducklings have reached the age of at least 4 weeks and are large enough to hold a standard-sized leg band, and ends immediately before the hunting season, which can begin in early October. To increase the number of Aix sponsa L. (Wood Duck) banded each year in the Atlantic Flyway, several state agency biologists have considered banding Wood Ducks in June. In the southern US, Wood Ducks begin nesting in late January or early February compared to early April in the northern portion of their range (Bellrose and Holm 1994), and hatching may begin in early to mid-March (Davis et al. 2007); therefore, many young birds are large enough to be captured and banded in June rather than waiting until July or later. Our findings from a literature review suggested that the preseason banding period was arbitrarily defined as 1 July–30 September because this period relates to the late summer–early fall pre-hunting season population (Anderson and Henny 1972). At the summer 2012 meeting of the Atlantic Flyway Migratory Game Bird Technical Section, the Wood Duck Committee asked for a review of existing June Wood Duck banding data prior to any states expending extra effort or funds to capture and band Wood Ducks in June. To help address that concern, we analyzed Wood Duck banding data and tested the null hypothesis that direct band-recovery rates of Wood Ducks banded in June did not differ from direct band-recovery rates of Wood Ducks banded during the traditional 1 July–30 September period. Methods For the Atlantic Flyway states, we obtained Wood Duck banding and recovery data from the US Geological Survey (USGS) Bird Banding Laboratory and summarized them by state and month for 1998–2007, the most recent 10-year period of stable regulations. Our query did not include females that were caught in nest boxes, but did encompass all age and sex classes that were captured and banded during normal banding operations. Banding data from the USGS Bird Banding Laboratory are most readily available as summaries by 5-day period (e.g., June 1–5, 6–10, 11–15… and 26+); therefore, we couched appropriate analyses during these same temporal periods. For states with a substantial number (>300) of June Wood Duck bandings and that also had comparable banding data from July, August, and September, we calculated direct band-recovery rates for each state and month in each of the 10 years. A direct band recovery is defined as a recovery that occurs during the hunting season immediately following the banding period, whereas an indirect recovery occurs in a subsequent hunting season. We chose direct bandrecovery rates as the metric of comparison; we assumed that if Wood Ducks banded in June died or lost their bands at a higher rate than Wood Ducks banded during July–September, then the direct band–recovery rate of June-banded Wood Ducks would be lower than the direct band-recovery rate of Wood Ducks banded during the traditional preseason period. We converted direct band-recovery rates, which Southeastern Naturalist G.D. Balkcom, P.R. Garrettson, and R.J. Benedict, Jr. 2014 Vol. 13, No. 3 602 are expressed as percentages or proportions, with arcsine-square root transformation prior to analysis to stabilize the variances because in a binomial distribution the variance is a function of the mean (Ott 1988, Sokal and Rohlf 1981). We used one-way analysis of variance to test for differences in direct band-recovery rates by state, month, year of banding, and all interactions. We then pooled data across states and years to test for differences by month of banding. We used Program R version 2.15.1 (R Foundation for Statistical Computing, Vienna, Austria) for analyses. Following the analysis of variance, we used Tukey’s honest significant difference, Student-Newman-Keuls, and Fisher’s least significant difference procedures to examine pairwise comparisons to determine any differences among months (Ott 1988). Of the 3 methods, Tukey’s honest significant difference is the most conservative in detecting differences, the Student-Newman-Keuls procedure is moderately conservative, and Fisher’s least significant difference procedure is the least conservative (Ott 1988). To better understand changes in direct bandrecovery rates across the entire banding season, we plotted direct band-recovery rates by 5-day banding period, and fit a quadratic equation to the data. There are twenty-four 5-day periods between 1 June and 30 September. However, no direct band recoveries occurred for Wood Ducks banded after 25 September; therefore, we used 23 periods in the analysis. Results Only Florida, North Carolina, and South Carolina had a sufficient number of bandings during each month from June–September to warrant inclusion in our analyses (Table 1). Of 120 possible state-month-year banding combinations (3 states x 4 months x 10 years), banding occurred in 115 of those periods. The direct band-recovery rate averaged 0.053 (SD = 0.001, n = 25,426, where n = number of bandings) over the entire time period. Transformed direct band-recovery rates were not different by state (P = 0.063; F = 2.848; df = 2, 91) or year (P = 0.674; F = 0.178; df = 1, 91), and there were no significant interactions: month*year (P = 0.666; F = 0.525; df = 3, 91), month*state (P = 0.767; F = 0.552; df = 6, 91), Table 1. Number of Wood Ducks banded in June by state in the Atlantic Flyway, 1998–2007. State Bandings Delaware 12 Florida 768 Georgia 40 Massachusetts 1 Maryland 56 Maine 29 North Carolina 1290 New York 30 Pennsylvania 5 South Carolina 2114 Virginia 1 Vermont 328 Southeastern Naturalist 603 G.D. Balkcom, P.R. Garrettson, and R.J. Benedict, Jr. 2014 Vol. 13, No. 3 year*state (P = 0.775; F = 0.256; df = 2, 91), month*year*state (P = 0.225; F = 1.395; df = 6, 91); therefore, we pooled data across states and years and found transformed direct band-recovery rates differed by month of banding (P = 0.00987; F = 3.973; df = 3, 111). Direct band-recovery rates averaged 0.035 (SD = 0.003, n = 4172) in June; 0.051 (SD = 0.002, n = 8925) in July; 0.062 (SD = 0.002, n = 9884) in August; and 0.059 (SD = 0.005, n = 2445) in September (Table 2). The more conservative Tukey’s honest significant difference procedure and the Student- Newman-Keuls procedure indicated that transformed direct band-recovery rates from birds banded in June were not different than those from July or September, but were different than those from August. The Fisher’s least significant difference procedure indicated that transformed direct band-recovery rates from birds banded in June were not different than those from September, but were different than those from July and August. No other month to month comparisons differed. We conducted another analysis of the direct band-recovery rate by 5-day banding period and found that a quadratic equation: direct band-recovery rate = 0.0001572x2 + 0.005248x + 0.0176, where x = 5-day banding period, fit the data better (P = 0.00055; F = 16.849; df = 1, 20; R2 = 0.7473) than a linear model (R2 = 0.5344, Fig. 1). Discussion Our finding of lower recovery rates of Wood Ducks banded in June is in accordance with LeMaster and Trost (1994), who reported generally lower direct recovery rates of birds banded early (15 April–30 June) compared to late (1 July–15 September). A possible explanation for the difference in direct recovery rates is a violation of the assumption of no mortality between banding period and recovery period. We attribute this putative mortality to two factors: (1) there is a greater period of time that birds banded early must survive until the beginning of hunting season, and (2) lower summer survival of birds banded in the South. LeMaster and Trost (1994) reported noticeably lower summer survival rates for both adult male and adult female Wood Ducks in southern and southeastern geographic areas than for northeastern, north-central, and Great Lakes states regions. Davis et al. (2001) found relatively robust (>90%) survival of brood-rearing females in Alabama and Mississippi, but an overall duckling survival of only 21–29% (Davis et al. 2007), Table 2. Direct band-recovery rates of Wood Ducks banded in Florida, North Caroina, and South Carolina by month, 1998–2007. Direct Band-Recovery Rate June July August September State Mean SD Mean SD Mean SD Mean SD Florida 0.035 0.007 0.039 0.005 0.049 0.005 0.055 0.009 North Carolina 0.038 0.005 0.047 0.004 0.066 0.003 0.055 0.007 South Carolina 0.033 0.004 0.059 0.004 0.061 0.005 0.069 0.010 Average 0.035 0.003 0.051 0.002 0.062 0.002 0.059 0.005 Southeastern Naturalist G.D. Balkcom, P.R. Garrettson, and R.J. Benedict, Jr. 2014 Vol. 13, No. 3 604 although duckling survival varied by site-habitat. Predation was an important mortality factor for ducklings in their study (Davis et al. 2007). Given that our sample was biased towards the southern US, where we derived our data from Florida, North Carolina, and South Carolina, and that summer survival of adult Wood Ducks is lower in southern areas, we believe that June bandings (at least in southern areas) may violate the assumption of no mortality between banding and recovery periods, and that results from June-banded birds may not be comparable to results from birds banded July–September. Our results also suggest a larger question about the degree to which bandings even during the traditional July through September preseason period violate the assumption of zero mortality due to differences in exposure to threats. A bird banded 1 July must survive 92 days prior to the beginning of the hunting season, whereas if banded 30 September it needs only survive 1 day. We suggest that techniques for calculating nest survival might be adapted for use with banding data. Specifically, the number of days between banding and the beginning of the hunting season could be used as a standardized individual covariate in survival analyses within program MARK (Nicolai et al. 2006). Such efforts are beyond the scope of this paper, but large banding and recovery datasets for many species would lend themselves to those types of analyses. Another possible explanation for the difference in direct recovery rates would be the violation of the assumption that leg bands are not lost or overlooked by hunters. Leg bands typically have high retention rates, and authors may choose to disregard Figure 1. Direct band-recovery rates of Wood Ducks banded in Florida, North Caroina, and South Carolina by 5-day banding period, 1998–2007. Southeastern Naturalist 605 G.D. Balkcom, P.R. Garrettson, and R.J. Benedict, Jr. 2014 Vol. 13, No. 3 band-retention rates in their analysis, especially when considering only direct recoveries (Krementz et al. 1996). Retention rates for standard aluminum leg bands are 0.9995 in North American Geese (Zimmerman et al. 2009); retention rates for plastic leg bands are 0.998 in adult Pacific Brant (Ward et al. 1997), and retention rates for plasticine-filled leg bands in day-old ducklings are 0.973–0.986 (Blums et al. 1999). Because of the typically high retention rates and because we are only considering direct band recoveries in this analysis, we do not believe that band loss was a factor in explaining the differences in band-recovery rates by month of banding. We suggest that state or federal agencies that band Wood Ducks, especially in southern latitudes, should maintain banding efforts during the traditional banding period 1 July–30 September. We also advocate particular emphasis on banding between mid-July and mid-September because bands established during that period have the highest direct recovery rates of the banding periods examined. States should be aware that Wood Ducks banded in June have lower direct recovery rates, and data collected from June-banded Wood Ducks should be used with caution. Future research should be directed towards exploration of potential age and sex differences as well as determining other factors that lead to lower recovery rates for June-banded Wood Ducks, especially in southern areas. Acknowledgments We would like to thank the Atlantic Flyway Migratory Game Bird Technical Section’s Wood Duck Committee for posing this question, and the Wildlife Restoration Program for partial funding of this project. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the Georgia Department of Natural Resources, US Fish and Wildlife Service, or the Florida Fish and Wildlife Conservation Commission. Literature Cited Anderson, D.R., and C.J. Henny. 1972. Population ecology of the Mallard. I. A review of previous studies and the distribution and migration from breeding areas. Resource Publication 105. US Fish and Wildlife Service, Washington, DC. 166 pp. Bellrose, F.C., and D. Holm. 1994. Ecology and Management of the Wood Duck. Wildlife Management Institute. Stackpole Books, Mechanicsburg, PA. 588 pp. Blohm, R.J., D.E. Sharp, P.I. Padding, R.W. Kokel, and K.D. Richkus. 2006. Integrated waterfowl management in North America. Pp. 199–203, In G.C. Boere, C.A. Galbraith, and D.A. Stroud (Eds.). Waterbirds Around the World: A Global Overview of the Conservation, Management and Research of the World’s Waterbird Flyways. 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