Co-Authors. Doug Howell, Waterfowl Biologist. North Carolina Wildlife Resources Commission. Wildlife Management Division. Surveys and Research Program

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2 Co-Authors Doug Howell, Waterfowl Biologist North Carolina Wildlife Resources Commission Wildlife Management Division Surveys and Research Program Joe Fuller, Migratory Game Bird Coordinator North Carolina Wildlife Resources Commission Wildlife Management Division Surveys and Research Program Roald Stander, M.S. Student University of Manitoba Department of Environment and Geography Master of Environment Program Special Thanks! You are viewing this document because you have played an integral role in insuring this project s successful fruition. Whether you are a property owner, research advisor, local wildlife professional, project sponsor, or simply a helping hand, your help does not go unnoticed. I would like to thank every person involved. - Daniel Lawson Graduate Research Assistant

3 Lawson 1 Background The American black duck (Anas rupripes) population has been in decline since the 1950s. According to United States Fish and Wildlife Service (USFWS) mid-winter survey estimates, black duck numbers decreased more than 50% from the 1950s to the 1990s (Figure 1) (USFWS 2017). Since this time, the black duck population has stabilized in the Atlantic Flyway (Figure 2). Mid-winter Survey for American Black Ducks ( ) Figure 1: USFWS Mid-winter Waterfowl Survey Estimates for the American Black duck in the Atlantic and Mississippi Flyways ( ) Figure 2: USFWS Mid-winter Waterfowl Survey Estimates for the American Black Duck in the Atlantic Flyway ( ) There are several potential explanations for this decline, including loss in the quantity and quality of breeding and wintering habitats, overharvest, and interactions (competition, hybridization) with mallards (Anas platyrhynchos) during the breeding and wintering periods (Anderson et al. 1987, Conroy et al. 2002). The historical loss of coastal wetlands in the Mid-Atlantic region has been significant (Dahl 1990) and their continued degradation (Tiner 1987, Dahl 2000, Dahl 2006, Stedman and Dahl 2008, Dahl and Stedman 2013) may limit the ability of this area to support black duck populations at conservation goals (Morton et al. 1998, NAWMP 2014). Although there have been ongoing efforts to understand the limiting factors of Mid-Atlantic black ducks during the nonbreeding season (Cramer et al. 2012, Livolsi 2015, Ringelman et al. 2015), there is a need to better understand the breeding season limiting factors as well, especially in light of analyses that suggest longterm declines in recruitment (Brook 2006). Consequently, the Black Duck Joint Venture has determined that there is a need to quantify regional differences and factors influencing black duck productivity. Black ducks breed in highest concentrations in the eastern Canadian provinces (Rusch et al. 1989), and nesting studies in this region generally have found nest success is adequate to maintain the population and is similar to sympatric mallards (Petrie et al. 2000). A smaller population of black ducks nest in the Mid- Atlantic region, however less is known about their nest success. Until recently, the status of the breeding black duck population in North Carolina was poorly understood. North Carolina represents the southern extent of the species breeding range (Stewart 1958, Parnell & Quay 1962, Bellrose 1980). Although breeding black ducks in North Carolina are well documented, their long-term population trend and nesting success is unknown. We suspect that breeding populations have declined over time, similar to breeding populations farther north in Virginia and Maryland (Costanzo and Hindman 2007),

4 Lawson 2 but there is no empirical or baseline data to support this. There have been a few past attempts to quantify the status of breeding black ducks in North Carolina; however, these were spatially limited. Parnell and Quay (1962) reported black duck production between on Pea Island, North Carolina and conducted more thorough nest searching and nest success research in They found black duck nesting was beginning to decline and noticed lower apparent nest success (69%) than those observed in the Chesapeake Bay (91%) or Canada (81%) (Stotts 1956, Wright 1954). Additional research in 1990 (Fleming et al. 2000) on Piney Island, North Carolina located 12 nests with an apparent nest success of only 67%. In 2013, the North Carolina Wildlife Resources Commission (NCWRC) initiated an aerial black duck population survey to better understand the distribution and density of breeding black ducks in suitable coastal marsh habitat in North Carolina (NCWRC unpublished data). This survey is based upon the Atlantic Flyway Breeding Waterfowl Plot Survey (AFPS; Heusmann and Sauer 2000). During , the methodology and survey area was refined to produce more precise breeding population estimates. In 2016, the sampling frame contained 1,267 1-km² plots containing between 5-40% marsh habitat, and 595 plots containing >40% marsh habitat which was deemed suitable for nesting black ducks. Of these plots, a randomly sampled subset of 134 plots was surveyed via helicopter. Extrapolating the results of the survey of this subset of plots to the entirety of North Carolina coastal marsh habitat, results in an estimate of 2,404 (90% CI = 1,131-3,678) total black ducks and 694 (90% CI = ) nesting pairs. However, there is no knowledge about their nest success and the factors that could influence those values. Proposed Research As per research objective request from the Black Duck Joint Venture, NCWRC along with the University of Delaware Department of Entomology and Wildlife Ecology (UDel) initiated a project that would quantify the breeding effort of the American black duck in coastal North Carolina. Specifically, it is our (NCWRC and UDel) goal to estimate reproductive parameters of breeding black ducks in coastal habitat in North Carolina as a function of nesting habitat quality, human disturbance, predation, flooding, and marsh burning. Breeding Black Duck Survey 2017 Introduction: The North Carolina Wildlife Resources Commission Breeding Black Duck Survey conducted in 2017 is built upon surveys conducted each year since Since the pilot survey in 2013, NCWRC has developed a method to index the breeding black duck population in suitable coastal marsh habitat in North Carolina. Results: This year 131 of 135 randomly chosen 1-km² plots were surveyed in three days, April 9-11, Three were not surveyed due to restricted airspace at the Dare County Bombing Range and one plot could not be surveyed due to residential development. The survey team counted 158 total black ducks. Per Atlantic Flyway Plot Survey (AFPS) protocols, this represented 75 indicated pairs (IP) (Table 1). Table 1: Group Size of Observed Black Ducks, April Group Size Number of Observations Mean counts of indicated pairs (IP's) of black ducks were highest in plots containing >40% marsh. However, plots containing 5-40% marsh contributed 44% of the total IP estimate due to the large number of plots in this survey stratum.

5 Lawson 3 The total population estimate included 1,048 IP's and 2,270 total indicated birds (TIB) (Table 2). Table 2: Population estimates of black ducks by survey strata in coastal North Carolina, April Stratum No. of Plots Total No. Total Indicated Estimated Estimated Total Surveyed of Plots Pairs/ Plot Indicated Pairs Indicated Birds Plots with >40% Marsh ( ) 1,163 (586-1,740) Plots with 5%-40% Marsh 88 1, ( ) 1,107 (574-1,639) Total Survey Area 131 1,862-1,048 (706-1,389) 2,270 (1,520-3,019) Discussion: This survey represents the 5th year of a multi-year effort to develop an aerial survey to estimate the size of the breeding black duck population in suitable coastal marsh habitat in North Carolina. Since no changes were made to the survey design in 2017, only results from 2016 and 2017 surveys are directly comparable. Although the estimate of IP's increased considerably from 2016, the 90% confidence intervals overlap, suggesting that increases may in part be related to sampling error. Interestingly, TIB's in 2017 was very similar to Total indicated birds is influenced by observations of grouped black ducks (>4 observed). Grouped black ducks may represent migrant black ducks that have not left the state or local, nonbreeding birds (during the survey window). Previous modifications to survey design have been made with the goal of reducing standard errors of survey estimates. Due to three plots having an outlier number of IP's observed, standard error increased considerably from 2016 (SE=110) to 2017 (SE=205). Moving forward, there is likely no way around this issue apart from adding additional survey plots. The inability to determine the sex of any observed black ducks from the air introduces some bias into the estimate of IP s and TIB s. Per AFPS protocols, a conservative approach was used when recording groups of black ducks of unknown sex. The inability to distinguish the sex of black ducks has the potential to influence IP estimates, both positively and negatively. For example, groups of three black ducks were treated as two IP s. If these three black ducks were identified as three drakes, they would have been treated as three IP s. Alternatively, observations of single black ducks were counted as one IP. However, some portion of the single black ducks observed were likely hens disturbed from their nest. In 2017, the survey team was able to positively identify one hen flushing from a nest and did not include this observation as an IP. NC American Black Duck Nesting Study Introduction: The North Carolina Wildlife Resources Commission and the UDel coordinate the American black duck breeding ecology study. This year we conducted nest searches for incubating black ducks on six 100 m 2 study sites in coastal North Carolina. We monitored these nests at seven-day intervals until they were terminated (hatched, depredated, flooded, etc.). Vegetation measurements were then taken at nest termination. A select number of nests were additionally monitored via trail camera in hopes to better record causes of nest failure and to synthesize an incubation break chronology for black ducks in the southern Atlantic Flyway. Further, we collaborated with Delta Waterfowl Foundation to test the efficacy of nest searching with aerial drones employing thermal imaging cameras.

6 Lawson 4 Nest Searching: Although there have been a few previous attempts to quantify the breeding status of black ducks in coastal North Carolina (Parnell & Quay 1962, Fleming et al. 2000), there were not any datasets available that identified optimal black duck nesting habitat in this region. To determine how and where to search for these nests, we drew from studies conducted farther north, in the Chesapeake Bay region (Krementz 1991, Costanzo and Hindman 2007, Haramis 1996, Stotts and Davis 1960). Based on our findings, we decided to focus on three habitat types: upland buffers (upland habitat that borders wetlands), islands, and tidal brackish marsh. Further, we chose six focal areas that contained these habitats and, per the NCWRC breeding black duck surveys, breeding black duck pairs. For the sake of logistics, we placed four sites northeast of the Pamlico River mouth along the inner banks of the Pamlico Sound stretching to the intersection of US 64 and the Croatan Sound (Figure 3). We placed two study sites encompassing parts of Pea Island and Roanoke Island on the Outer Banks of North Carolina (Figure 4). Figure 3: Inner Banks Study Sites. Hyde and Dare Counties, North Carolina Figure 4: Outer Banks Study Sites. Dare County, North Carolina

7 Lawson 5 Our nest searching technique was modified from all-terrain vehicle (atv) chain drags used for locating upland nesting waterfowl (Klett et. al. 1986), where a chain suspended between two atvs is pulled across standing vegetation. The chain covers all vegetation in between the atvs and chain links rattle to produce a metallic sound that causes nesting hens to flush as the atvs progress forward. Since our study sites were not accessible to atvs, we decided to modify the dragging apparatus so it could be used by two technicians on foot. Nylon rope seemed to be the most sensible alternative. We used 100 ft. lengths of rope and attached aluminum cans spaced at ~2m intervals along the entire length of the rope. Every can received small (~3-4 cm) rocks to serve as noisemakers in lieu of shifting chain links. Two technicians conducted nest drags. One technician would stretch the rope to the edge of a wetland, typically on the edge of a body of water. The other technician would stretch the other end of the rope directly inland from the wetland edge. Once the rope was extended, both technicians traveled forward while remaining parallel to one another and the wetland edge (Figure 5). An additional technician was used as a spotter that constantly watched the dragline to identify flushing hens. The spotter would identify the exact location of the flushing hen and guide the other technicians to the nest. Technicians continued forward until a hen was flushed. Once a hen was flushed, one technician would approach the nest and begin data collection while the other stayed at least 5 meters away and recorded data. In areas where we could not drag the rope due to vegetation height and rigidity, technicians distanced themselves 5 25m apart and walked transects of the selected area. We utilized this technique specifically on spoil islands in the Pea and Roanoke Island study sites (Figure 4). Figure 5: Nest Dragging in North Carolina Brackish Marsh We initiated nest searching on April 1 ST and continued until June 17 th. During that time we found our nest dragging technique to be a great success and almost necessary to find the sparsely positioned black duck nests in the many thousands of acres of coastal salt marsh that were surveyed. This season we found and monitored a total of 56 duck nests. The majority of nests were black duck (n=47, 84%). Mallard and gadwall (Mareca strepera) made up the remaining nests at 4 (7%) and 5 (9%), respectively (Figure 6). Figure 6: 2017 Nests Species Composition The inner banks study areas (Figure 3) contained mostly brackish marsh and upland buffer habitat. We found 55% (n=31) of the nests in these areas. The remaining 45% of nests

8 Lawson 6 (n=25) came from the island habitats of the outer banks. American black ducks favored nesting on the slightly elevated beach ridges of the inner banks brackish marsh. Beach ridges were slightly higher than the adjacent low marsh because of sand deposition due to years of wave action. These ridges were directly adjacent to the open water of back bays and points jutting into the sound. The dominant plant species on the brackish marsh beach ridges (high marsh) were: black needlerush (Juncus roemerianus), saltmarsh cord grass (Spartina alterniflora), saltmeadow cord grass (Spartina patens), and saltgrass (Distichlis spicata). These species made up the high marsh, with each species dominating in patches or zones to form a mosaic vegetation pattern (Figures 7-8). Figure 8: High Marsh Dominated by Spartina patens On our two Outer Banks study sites (Roanoke Island and Pea Island) we spent a great majority of our time searching natural and man-made islands within the Pamlico Sound. These islands proved to be very diverse in topography, vegetation structure and composition, and black duck nesting productivity. Topography reflected how the island was formed, whereas vegetation structure and productivity reflected how long ago. Man-made (dredge islands) where typically elevated and contained an array of plant communities (Figures 9-10). Some of which were: dune grasslands, maritime shrublands, upper and lower beach, and maritime vine tangles. Typically, the older the island, the later the successional stage. Naturally formed islands were low lying and were broadly classified as brackish marsh. As mentioned earlier, each island had unique black duck nesting productivity. Most of the variability was attributed to predator influence and vegetation structure. Figure 7: Brackish High Marsh Mosaic

9 Lawson 7 Figure 9: Man-made Dredge Island > 10 Years Old Figure 11: Elevated Black Duck Nest in Brackish Marsh Figure 10: Man-made Dredge Island < 10 Years Old Collectively, nests were located an average of 25.6 meters from open water. Nests located in flood prone spots, brackish marsh especially, were slightly elevated (15-30 cm) structures that consisted of needlerush or Spartina spp. leaves (Figure 11) and resembled overwater-nesting diving duck nests. Nests in the brackish marsh that were not elevated, were tucked deep into surrounding cover (Spartina patens, Distichlis spicata, and Juncus roemerianus) and the bowl was low in profile and mainly constructed of Spartina patens (Figure 12). Both varieties had down lining the nest bowl, but a profuse lining seemed to be less common in elevated structures. Figure 12: Low-Profile Black Duck Nest in Brackish Marsh On islands in the Outer Banks study sites, black duck nests were located within dense vegetation in any combination of warm season grasses, Rubus, and forbs (Figures 13-14).

10 Lawson 8 maximum average vegetation height. We found percent composition at the microhabitat scale to be; 65% grass, 14% litter, 7% forbs, 5% woody vegetation, 5% water, and 4% bare soil. Our average VOR was 0.5 meters meaning there was more than 50% visual coverage by vegetation below that height. Finally, max average vegetation height yielded 0.9 meters. Figure 13: Black Duck Nest in Pioneer Island Vegetation Figure 14: Black Duck Nest in Dense Island Vegetation We took vegetation measurements at nest sites once nests were fated (e.g. abandoned, depredated, etc.). We hoped to get an idea of the exact microhabitat black ducks chose for nesting in North Carolina. To achieve this, technicians collected percent composition with a Daubenmire frame and Visual Obstruction Readings (VOR s) with a Robel pole (Robel et al. 1970). Along with the VOR s, we recorded Earliest and latest nesting initiation, peak(s) of nesting initiation, and nesting season duration are questions that have never been confidently answered of black ducks nesting in coastal North Carolina. Foremost, we estimated nesting initiation questions by backdating to the initiation date (the day the first egg was laid). We did this by adding the number of eggs in the nest to the incubation stage in days, and then took the sum and subtracted it from the date we discovered the nest. Nesting season was simply the date the first nest of the season was initiated until the final nest was terminated. The earliest date we found black ducks initiating nests was March 3; the latest date was May 24 (Figure 15). This year we noticed two separate nest initiation peaks. The first was during the first two weeks of April (4/2-4/15). The second peak was over the first two weeks of May (4/30 5/13). One possible explanation for the separate peaks is an inclement weather event that occurred in midlate April. During this time, several flood events caused a high rate of nest failure in brackish marsh adjacent to the Pamlico Sound. A few of our monitored nests remained under water for an extended period of time. It is possible that the peak at the beginning of May could have been a renesting effort.

11 Lawson 9 Figure 15: 2017 Black Duck Nest Initiation Chronology Nest Monitoring: This season we monitored 47 black duck nests at 7-10 day intervals (Klett et al. 1986). The product of our monitoring efforts allowed us to have several exposure days to insure that our incubation stage estimates were accurate. Multiple visits also insured more precise nest fates, because it reduced the time terminated nests were exposed to the elements. The composition of nest fates for the 2017 season are as follows in (Table 3). Table 3: 2017 Nest Fate Composition Fate Black Duck Nests Hatch 9 Abandoned 21 Depredated 12 Nonviable 3 Unknown 2 related to the nest (i.e. hen present, eggs warm and covered, eggs cold and uncovered, etc.). Along with collecting this data, we covered the nest with down and other present nest bowl materials and then made a distinct X on top with two pieces of contrasting vegetation. Likewise, we used the progression of embryo development to determine if the hen was still actively incubating the nest. There were several factors we identified that caused hens to abandon nests. (Figure 16). We identified hatched nests according to (Klett et al. 1986). In the nest, we looked for presence of detached shell membranes and yellowish feather sheaths or small egg fragments without membranes in nest material, or presence of ducklings in the nest bowl. Identifying abandoned nests was a little bit trickier. On initial nest visits, we noted the hen status as it Figure 16: 2017 Nest Abandonment Causes The factor that attributed most to nest abandonment was unfortunately, our own initial

12 Lawson 10 activity at the nest site. Of this percentage, all nests were still in lay or very early in incubation (< 7days). Of the twelve depredated nests, we identified several nest predators. Nest predators identified included American and fish crow (Corvus brachyrhynchos and Corvus ossifragus, respectively), bald eagle (Haliaeetus leucocephalus), raccoon (Procyon lotor), American mink (Neovison vison), and red imported fire ant (Solenopsis invicta). Nonviable nests were nests where all eggs addled before any other fate. To aid in fating nests, we placed trail cameras on 35 black duck nests. Trail Cameras: Placing trail cameras on nests helped us to understand the nesting ecology of the black duck in North Carolina. By formatting cameras to capture images every minute, we were able to record the frequency and duration of incubation breaks. Cameras captured many events that had an impact on the nest fate. Some of these events included: flooding, depredation, prolonged incubation breaks, and abandonment. Sample trail camera photos are pictured in (Figures 17-20). Figure 18: Black Duck Hen Elevating Nest Bowl Prior to High-water Event Figure 19: Bald Eagle Depredation Figure 17: April 25 Flooding Event with Submerged Black Duck Nest Pictured in Top-center Figure 20: Raccoon Depredation

13 Lawson 11 Collaborative Drone Research Figure 21: Delta Waterfowl Research Drone Introduction: This year we had the opportunity to collaborate with Delta Waterfowl Foundation and the University of Manitoba on research testing the efficacy of thermal-imagery equipped drones in avian nest searching. Due to the sparseness of black duck nests within the brackish marsh of coastal North Carolina, we saw this as an opportunity to increase our nest searching capacity while contributing to dronebased wildlife sampling research. Roald Stander, the drone research graduate student with University of Manitoba, brought his research to our study sites May Results: We chose study plots acres in size that contained known active black duck nests. We surveyed sites between midnight and sunrise. Detectability of the thermal targets by the thermal camera varied from site to site; on the same site over multiple days; or even on the same site during a single survey. Different habitats had certain physical characteristics which increased/decreased the likelihood of detecting the targets. Certain meteorological conditions seemed to greatly influence detectability. Humidity ultimately negatively influenced detectability. Thermal reflectance from moonlight was also observed. Our goal was to fly three successional missions over different nights recording coordinates of each target. The aim of flying multiple times over the same area was to rule out transient birds, in that targets observed three nights in a row would be indicative a nesting bird. Flying three nights was not achieved at all sites due to inclement weather. All of the sites that we visited had a relatively low number of known nests. The thermal camera does not detect heat signatures, but rather detects relative temperature differences. When the habitat being surveyed is of a homogenous temperature, detectability is very high. The avian thermal targets are the hottest objects within the field of view (FOV) of the camera and typically show up clearly. Discussion: Surveying coastal regions provides unique challenges due to the humid conditions. Black ducks in the region typically select salt marsh hay grass (Spartina patens) as nesting cover. The structure of the grass seems to inherently hold moisture due to the c-shaped structure of the blade. The high levels of lowlying humidity seems to be exacerbated by the fact that this is a tidal area. Despite all the challenges, we located 2/2 known black duck nests and 14 Clapper rail nests. The known nests were relatively open from above, and the rail nests were located in black needlerush. One of the two active black duck nests included in the survey was extremely visible from 150 meters (Figure 22) using a transect-based survey method. We were able to hover over the nest at a relatively low height, <5 meters, without causing the hen to flush (Figure 24). We noticed a raccoon momentarily disappear as it was moving through matted patches of vegetation, including Spartina patens. This prompted us to test the detectability of a hot thermal target (>60⁰C) placed in typical nesting cover. The thermal camera could only detect the target at 7 AGL.

14 Lawson 12 The habitat inherently had challenges associated with working in tidal areas. The observed detectability warrants further testing. Although we found all known nests, the results were inconclusive. Figure 22: Nesting Black Duck Thermal Imaging Snapshot from 150 meters Figure 23: Nesting Black Duck Thermal Imaging Snapshot from 50 meters Figure 23: Nesting Black Duck Thermal Imaging Snapshot from <5 meters

15 Lawson 13 Literature Cited Anderson, D. R., K. P. Burnham, J. D. Nichols, and M. J. Conroy The need for experiments to understand population dynamics of American black ducks. Wildlife Society Bulletin 15: Bellrose, F. C Ducks, geese and swans of North America. Third edition. Stackpole, Harrisburg, Pennsylvania, USA. Brook, R. K. Ross, K, Abraham, and C. Davies Black duck population trends in the western part of their range. Black Duck Joint Venture final report. Conroy, M. J., M. W. Miller, and J. E. Hines Identification and synthetic modeling of factors affecting American black duck populations. Wildlife Monographs 50:1 64. Costanzo, G. R., and L. J. Hindman Chesapeake Bay breeding waterfowl populations. Waterbirds 30: Cramer, D. M., P. M. Castelli, T. Yerkes, and C. K. Williams Food resource availability for American black ducks wintering in southern New Jersey. Journal of Wildlife Management 76: Dahl, T. E Wetlands losses in the United States, 1780's to 1980's. Report to the Congress (No. PB /XAB). National Wetlands Inventory, St. Petersburg, Florida, USA. Dahl, T. E Status and trends of wetlands in the conterminous United States 1986 to United States Fish and Wildlife Service, Washington D.C., USA. Dahl, T. E Status and trends of wetlands in the conterminous United States 1998 to United States Fish and Wildlife Service, Washington, D.C., USA. Dahl, T. E., and S. M. Stedman Status and trends of wetlands in the coastal watersheds of the conterminous United States 2004 to United States Fish and Wildlife Service and National Marine Fisheries Service, Washington, D.C., USA. Daubenmire, R A canopy coverage method of vegetation analysis. Northwestern Science 33: Flemming, W. J., Dubovsky, J., Collazo, J. A., Temple, E. R., & Conomy, J. T. (2000, August). An overview of studies to assess the effects of military aircraft training activities on waterfowl at Piney Island, North Carolina. In Terra Borealis Effects of Noise on Wildlife Conference, Happy Valley-Goose Bay, Labrador. Haramis, G. M., D. G. Jorde, G. H. Olsen, D. Stotts, and M. Harrison Breeding productivity of Smith Island black ducks. Pages in Breeding productivity of Smith Island black ducks. Black ducks and their Chesapeake Bay habitats: proceedings of a symposium. USGS/BRD/ITR Information and Technology Report, Reston, Virginia USA. Klett, A. T., H. F. Duebbert, C. A. Faanes, and K. F. Higgins Techniques for Studying Nest Success of Ducks in Upland Habitats in the Prairie Pothole Region.

16 Lawson 14 Krementz, D. G., V. D. Stotts, D. B. Stotts, J. E. Hines, and S. L. Funderburk Historical changes in laying date, clutch size, and nest success of American black ducks. The Journal of Wildlife Management : Livolsi, M. C Bioenergetics, behavior, and sea level rise: current status and future implications for wintering dabbling ducks in Delaware. Thesis, University of Delaware, Newark, USA. Morton, J. M., R. L. Kirkpatrick, M. R. Vaughan, and D. F. Stauffer Habitat use and movements of American black ducks in winter. Journal of Wildlife Management 53: North American Waterfowl Management Plan Revised objectives; an addendum to the 2012 North American Waterfowl Management Plan. Canadian Wildlife Service, United States Fish and Wildlife Service, Secrataria de Medio Ambiente y Recursos Naturales. Parnell, J. F., and T. L. Quay The populations, breeding biology, and environmental relations of the black duck, gadwall and blue-winged teal at Pea and Bodie Islands, North Carolina. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 16: Petrie, M. J., R. D. Drobney, and D. T. Sears Mallard and black duck breeding parameters in New Brunswick: a test of the reproductive rate hypothesis. Journal of Wildlife Management 64: Ringelman, K. M., C. K., Williams, P. Devers, J. M. Coluccy, P. Castelli, K. A., Anderson, J. L. Bowman, G. R., Costanzo, D. M. Cramer, M. Dibona, M. Eichholz, M. Huang, B. Lewis, D. Plattner, and T. Yerkes. 2015b. A meta-analysis of American black duck winter habitat use along the Atlantic Coast. Journal of Wildlife Management 79: Robel, R. J., J. N. Briggs, A. D. Dayton, and L. C. Hulbert Relationships between visual obstruction measurements and weight of grassland vegetation. Journal of Range Management 23: Rusch, D. H., C. D. Ankney, H. Boyd, J. R. Longcore, F. Montalbano, J. K. Ringelman, and V. D. Stotts Population ecology and harvest of the American black duck. Wildlife Society Bulletin 17: Stewart, R. E Distribution of the black duck. U.S. Fish & Wildlife Service Circular 51, Washington D.C., USA. Stotts, V. D., and D. E. Davis The black duck in the Chesapeake Bay of Maryland: breeding behavior and biology. Chesapeake Science 1: Tiner, R. W Mid-Atlantic wetlands a disappearing natural treasure. U.S. Department of the Interior, Fish and Wildlife Service and U.S. Environmental Protection Agency, Washington, D.C., USA. Mid-winter Waterfowl Survey migbirdapps.fws.gov. USFWS. < Accessed 20 Sep 2017.

17 Lawson 15 Wright, B. S High Tide and East Wind. The Stackpole Company and the Wildlife Management Institute., Harrisburg, Pennsylvania.