The American Black Duck is a species of duck that closely resembles female mallards. The black duck is mostly dark brown in color with some black, has short legs, a yellow/green bill which looks duller on the females than does the males, and also the males have a blue patch bordered with black on its wing. There are other species of duck that look similar, for instance the Mottled duck and the Gadwall. (8) Both the male and female look very similar with the females being a lighter tone and both have the a lighter head and neck than the rest of their body. The average size for the black duck is 20-24 inches in length and weighs around 2.5lbs. (24)
The Black duck is a dabbling species of duck meaning that they tip their head into the water and lift their tails up in the air in order to search for food in the water or mud. As with other dabbling duck species the black duck takes off straight from the water to fly which is much different than diving ducks in that they have to run across the water to pick up enough speed to fly. (23)
Black ducks prefer living in coastal brackish marshes and bays not far from agricultural lands, focused near the water. They also favor wooded areas and will nest in many different types of housing such as old bird nests, muskrat lodges, on the ground or in tree cavities. Black duck also prefer being close to the edge of some body of water but can be found as far as one-half mile from the water’s edge. (1)
Black Duck seem to be able to adjust to noise that they hear on a continuous basis, such as aircraft near an air base, better than other species like the wood duck (Conomy.) This idea may suggest that the black duck (anas rubripes) may have more habitat availability if they can become accustomed to loud noise. (10) As noted in research dealing with noise effects on black duck populations it has also been found that hiking trails, 1 trail, near nesting areas may not directly affect nesting site success. Variables such as type of habitat that an area is in, predation rates, i.e. feral cats that have been accidentally released into an area with a nesting site, and the amount of cues from humans being near a site may affect nesting rates (Olson.) (11)
Black Ducks pairs are usually formed by autumn but can continue into winter, with nesting periods going from March through June, and incubation periods lasting 23-33 days. Seven to 12 eggs usually make up the clutch size, however if a clutch is destroyed birds may renest. The Fledge period usually lasts 8-10 weeks and maturity is reached at 1 year. (1) Pair bonds may be broken at varying times, with males typically remaining with their females about 2 weeks into the incubation period. (23)
Black duck mostly migrate along the Atlantic Coast from Maine to Florida, with most being found on coastal wetlands. Large amounts of the black duck seem to gather between Long Island and North Carolina for their Wintering grounds. When Black duck are away from the coast, they seem to use large river valleys such as those of the Tennessee, Detroit and upper Illinois rivers. (6)
The Black duck species seems to show dominance toward other individuals of the same species according to age class, whether or not individuals have a mate, and the sex of the individuals (Hepp.) (9)
Of the approximate 220,000 black duck that are counted for in the winter survey around 20,000 of those reside in the Chesapeake Bay area and along the eastern shore of Virginia, which are both wintering areas for black duck. Although the Eastern shore of Virginia is considered a wintering area it is also on the Southern edge of the black duck breeding territory. There are challenges to productive black duck breeding habitat that the species continues to face including: land use changes, erosion of marsh areas, and increases of predator communities. (19)
Average survival for male and female black ducks banded as adults show that in North Carolina the mean survival rates are as follows: adult males: 68.5% and adult females: 50.6%. The annual recovery rates for male and female black duck are as follows: adult males: 2.8% and adult females: 3.3%. Winter bandings show rates for adult male black ducks in North Carolina as follows: Canadian Recovery Rate: 0.5%, U.S. Recovery Rate: 2.6%, Average Mortality Rate: 31.5%, Canadian Kill Rate: 1.9%, U.S. Kill Rate: 7.8%, Due to Hunting: 30.8%. (21)
Food and Cover (including predators and predation)
Black ducks use a wide assortment of habitats and because of this it is difficult to determine specific requirements on a wide standard. Although as stated before these duck prefer wooded areas over the related Mallards. Black duck also use marshes for brood rearing and in the winter they congregate on large bodies of water on or near coastlines focusing on the plant food. (2)
Active Beaver ponds are directly correlated to increasing brood sizes and this can be credited as appropriate cover that has been formed from steady water levels. (5)
Depending on the area black duck ducks have a diet that is similar to mallards. They consume plant seeds but not those used in agriculture. Some seeds in their diet include: water smartweed, primrose-willow, wild-millet, and love grass, they also consume other forms of vegetation and animal matter also makes up a part of their diet. (14)
When black duck are using coastal marshes as their primary habitat they seem to be more omnivorous than many other duck species, which dabble, by consuming mollusks, crustaceans, and arthropods. Up half of their diet still consists of vegetable matter, such as seeds and roots. (17)
Cover that black rely on depends on the area to which they are in and the time of year, i.e. wintering season, breeding season, rearing season. Some cover types that black duck rely on are: lakes or ponds with emergent vegetation, lakes with rocky shores, lakes with unconsolidated shores, lakes or ponds with aquatic vegetation, and estuarine intertidal emergent areas. (20)
Coastal areas or areas that free of ice in the winter are required for feeding. Protection from Winter Storms is another key element that the black duck needs such as in open water or along high banks along open water or large estuaries. To ensure a greater chance of survival by getting enough food and the right kind of cover the black duck should go to both marine and estuarine habitats to have both variables offered. (22)
The three most devastating diseases to affect the black duck species include: Duck plague (a herpesvirus), avian botulism, and avian cholera. The National Wildlife Health Center has recorded the percentages of duck mortality rates between the years of 1970-1997; duck plague: 27.3%, avian botulism: 22.7%, avian cholera: 3%, other causes: 47%.
Sarcosporidiosis, a body parasite, has been reported in muscle tissue of black duck in Northern states. The nematode, which causes duckling mortality, also infects mature animals. (3)
The duck plague virus is transmitted through direct contact with individuals who have the disease or from direct contact with environments which harbors the virus, particularly water, and vertical transmission of the herpes virus can occur. Usually the disease is most rampant from late winter to late spring. The virus has also been detected in healthy populations of wild non-migratory waterfowl, such as the Canada goose and the Mallard. “The wild mallard has been identified as one of the primary waterfowl species associated with the annual initiation of duck plague die-offs, especially in Britian” (Van Dorssen and Kunst 1955). Black ducks are extremely susceptible to the virus, as populations are often found intermingling with mallards. (15)
As is the case with many game species, black duck management research and conservation is heavily funded. In 2009 Partner Contributions to the Black Duck Joint Venture Program (BDJV) collected $773,923 for research on Black Ducks, but total contributions reached 1,881,838 USD (7).
Due to the heavy funding for black duck management, there are more management practices in place for the species. For younger individuals of black ducks, regulations that are more restrictive can decrease the amount of hunting pressure and thus lead to increased survival rates. In aging populations the amount of survival plateaus and harvest rates no longer play a role in adult individual survival (Francis). (12)
Another important aspect of black duck management is habitat conservation and preservation. Although it is believed that habitat loss will affect black duck populations the outcome is not known for the species in direct relation to how habitat changes, i.e. forest removal, can affect the waterfowl populations (Rusch et al. 1989). (13) Speculations can be made about the effect of habitat loss, but more research is still needed for further study. Wetlands and other areas that black ducks are dependent upon should be managed thoroughly to help in achieve healthy populations of the species. Luckily, much of the land which black ducks are located is privately owned. This is significant because private owners are an untapped resource for helping to manage the black duck species. In addition to benefiting the waterfowl, private land habitat management can help to improve the landowner’s view of the land’s natural value and give landowner’s a better understanding of the land’s potential for future management reference. Research has shown that black duck habitat “Management practices may include moist-soil management of impoundments for invertebrate production, periodic burning of Scirpus marshes for seed production and rejuvenation, and trapping programs for targeted predator species” (Krementz). (18) Due to the sensitivity of black duck habitat, it is crucial to use all resources to ensure conservation and protection.
A key aspect of managing any animal species is knowing the population size. This information is used in order to find out births and deaths per year, and to manage the size of the population. Despite this importance, it has been found very difficult to survey the black duck species. One major factor for this inability to survey is due to their habitat, such as boreal forests of Eastern North America. In order for wildlife managers to get accurate estimates of total numbers for black duck that were harvested, killed, and those that survived black ducks must be banded. To get a more accurate estimate the banding must take place annually. (16)
In order to get a better understanding of black duck populations satellite telemetry studies are being conducted to obtain data of movement patterns including: migration routes, timing of migration, staging and stop-over areas, winter habitat use and breeding grounds affiliations. (19) Challenges (including climate change)
Though the Black Duck is not considered endangered the population has been on the downturn especially since the 1950s. As with many other species humans are causing extensive damage especially on breeding and wintering grounds. Black duck and Mallards are also hybridizing in turn only declining the population of the true Black duck even more. Presently some other threats on black duck populations include: acid rain,pesticide use, invasive species and wetland filling for developmental use.
Future threats to Black Duck populations will include loss of habitat from sea level rise and other habitat changes due to Global warming.(4)
In 1976 the secretary of the interior ruled that steel shot had to be used in areas where lead poisoning was prevalent where 5% of the gizzards in the local harvest of black ducks and mallards contained lead shot (Longcore et al. 1982). With the use of steel shot the amount of lead in gizzards of the ducks were reduced to 34 percent. Even with these positive notes ammunition manufacturers and waterfowl hunters greatly opposed the steel shot policy due to crippling loss, gun damage, and cost.(5) If food is available the body fat of black ducks will most likely remain constant, however just as with other animal species changes in their surrounding environment, i.e. habitat loss around a lake, forest or wetland, can also prevent black ducks from being healthy. During the winter months black ducks seem to have a harder time keeping their body mass up due to the fact that it is more difficult to forage during cold periods. (14)
1. Snyder, S. A. 1993. Anas rubripes. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). < http://www.fs.fed.us/database/feis/>. Accessed 20 Sept 2013.
2. Spencer, Howard E. 1986. Black duck. In: Di Silvestro, Roger L., ed. Audubon Wildlife Report. New York: The National Audubon Society: 855-869. 
3. Longcore, Jerry R., Daniel G. Mcauley, Gary R. Hepp and Judith M. Rhymer. 2000. American Black Duck (Anas rubripes), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online
4. Wells, V. (2007) Birder's Conservation Handbook: 100 North American Birds at Risk. Princeton University Press, New Jersey.
5. Bolen, E.G., Robinson, W.L. 2003. Wildlife Ecology and Management. Fifth Edition. University of North Carolina at Wilmington, North Carolina, and Northern Michigan University, USA.
6. Ducks Unlimited. 2013. American Black Duck. <http://www.ducks.org/hunting/waterfowl-id/american-black-duck>. Accessed 20 Sept 2013.
8. The Cornell Lab of Ornithology. 2011. American Black Duck. <http://www.allaboutbirds.org/guide/American_Black_Duck/id>. Accessed 9 Nov 2013.
9. Hepp, G. 1989. Benefits, Costs, and Determinants of Dominance in American Black Ducks.
<http://www.jstor.org.prox.lib.ncsu.edu/stable/info/4534772>. Accessed 9 Nov 2013.
10. Conomy, J. 1998. Do Black Ducks and Wood Ducks Habituate to Aircraft Disturbance? <http://www.jstor.org/stable/info/3802568>. Accessed 9 Nov 2013.
11. Olson, R. 1998. Effects of Human Disturbances on Success of Artificial Duck Nests <http://www.jstor.org/stable/3802569>. Accessed 10 Nov 2013.
12. Francis, C. 1998. Effect of Restrictive Harvest Regulations on Survival and Recovery Rates of American Black Duck. <http://www.jstor.org/stable/3802021>. Accessed 10 Nov 2013.
13. Nichols, J. 1991. Science, Population Ecology, and the Management of the American Black Duck. <http://www.jstor.org/stable/3809533>. Accessed 10 Nov 2013.
14. U.S. Fish and Wildlife Service (USFWS). 2012. Tennessee National Wildlife Refuge. New Program to Aid American Black Duck Research. <http://www.fws.gov/tennesseerefuge/blackduckresearch.htm>. Accessed 10 Nov 2013.
15. Thomas, N.J., D.B. Hunter, and C.T. Atkinson., editor. 2007. Infectious Diseases of Wild Birds. Blackwell Publishing Professional, Ames, Iowa, USA.
16. Rusch, D.H., C.D. Ankney., H. Boyd., J.R. Longcore., F. Montalbano. III., J.K. Ringelman., V.D. Stotts. 1989. Population Ecology and Harvest of the American Black Duck: A Review. <http://www.jstor.org/stable/3782702>. Accessed 10 Nov 2013.
17. BirdWeb. 2013. homepage. <http://http://www.birdweb.org/birdweb/bird/american_black_duck>. Accessed 10 Nov 2013.
18. U.S. Fish and Wildlife Service (USFWS). 1990. American Black Duck Anas rubripes. Patuxent Wildlife research Center Laurel, Maryland. <http://www.dnr.state.md.us/irc/docs/00000260_16.pdf>. Accessed 11 Nov 2013.
19. Virginia Department of Game and Inland Fisheries. 2013. American Black Duck Anas Rubripes. <http://www.dgif.virginia.gov/wildlife/waterfowl/black-duck/>. Accessed 11 Nov 2013.
20. U.S. Fish and Wildlife Service (USFWS). 2001. Gulf of Maine Watershed Habitat Analysis. American Black Duck Habitat Model. <http://www.fws.gov/r5gomp/gom/habitatstudy/metadata/black_duck_model.htm>. Accessed 11 Nov 2013.
21. U.S. Fish and Wildlife Service (USFWS). 1992. Population Characteristics and Simulation: Modeling of Black Ducks. <http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CHsQFjAJ&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3DADA322806&ei=Rz-NUrHOItSssATqo4HACg&usg=AFQjCNF5s-MzaD7Y1CfM-Aqi1gM0E21x0A&bvm=bv.56643336,d.cWc>. Accessed 11 Nov 2013.
22. Byerly, T., Fabritius, S,. 2013. Kids’ Inquiry of Diverse Species. American Black Duck. <http://www.biokids.umich.edu/critters/Anas_rubripes/>. Accessed 11 Nov 2013.
23. New Hampshire Public Television (NHPTV). 2013. Nature Works. American Black Duck. <http://www.nhptv.org/natureworks/americanblackduck.htm>. Accessed 11 Nov 2013.
24. Fuller, J., 2011. North Carolina Wildlife Resource Commission: Black Duck: North Carolina Wildlife profiles. <http://www.ncwildlife.org/Portals/0/Learning/documents/Profiles/blackduck091411.pdf>. Accessed 11 Nov 2013.
Marsh rabbits are medium-sized nocturnal rabbits with short, rounded ears and small feet. Adults can range from 14-16 inches and weigh 2-3.5 pounds. The rabbits are dark brown to reddish brown in color with a dark color belly. The distinguishing trait that separates the species from other cottontails would be the dark color of the underside of their tail; underneath other cottontail rabbit tails is white in color. This rabbit has three subspecies: the Carolina Marsh rabbit (Sylvilagus palustris palustris), Florida Marsh rabbit (Sylvilagus palustris paludicola)and Lower Keys Marsh rabbit(Sylvilagus palustris hefneri). The Lower Keys subspecies S. p. hefneri is the most identified subspecies. (1, 2)
The marsh rabbit’s range is restricted to the Coastal Plain of the southeastern U.S. It can be confined solely to marsh habitats starting from the Dismal Swamp of southeastern Virginia, through eastern North Carolina, southeastern South Carolina, southern Georgia, southern Alabama, and most of Florida (Chapman and Willner 1981; Chapman and Ceballos 1990). S. p. hefneri can be found exclusively in the Upper and Lower Keys of Florida. These rabbits are also most commonly found in brackish water areas, although at one point in time they were associated with freshwater marshes (Chapman). Unlike most rabbits, the marsh rabbit requires close access to water.
To date, little is known about the population size of the marsh rabbit. The marsh rabbit does not have a long lifespan; it is said to only live up to 4 years of age in the wild but one specimen at about 7 years old has set the captivity age maximum. The Lower Keys marsh rabbits were reported to be unevenly distributed throughout the Lower Florida Keys and have been listed on the IUCN Red List as an endangered species. The cause of the decline in this subspecies appears to be a result of habitat fragmentation and relatively small, isolated subpopulations (5).
These rabbits breed all throughout the year and with multiple partners during the breeding season. Researchers and scientists have categorized their unique breeding behavior as promiscuous. The female rabbit will average 6 liters per year with anywhere from 2-5 offspring. Although these animals mate all year long, the Lower Keys marsh rabbit appears to have the highest proportion of females with litters in March and September. The offspring are altricial - blind, and completely helpless. Their eyes do not open until they are about 4 to 5 days old, and the juvenile rabbits are nursed until they are 14 to 15 days old. Due to this behavior, the juveniles are more susceptible to predation. This is the reason why a large percentage of marsh rabbits do not survive past the age of one year (6; Chapman and Feldhamer, 1982, Jones, 1997).
Food and Cover (including predators and predation)
While herbivores have similar diets, there are many variations in the selection and eating habits between different species. Specifically, in marsh rabbits, which are herbivores, select different species of plants depending on the season. Selection is based on what is available to the rabbits, and what will sustain the rabbits nutritionally. Studies have shown that marsh rabbits tend to select plant species such as centella, marsh pennywort (Hydrocotyle sp.), cattail, rush (Juncus sp.), and water hyacinths (Piaropus crassipes) (Chapman and Willner 1981). Their diet may also consist of blackberry, greenbrier, and other woody and semi-woody plants. Food selection can also vary on the location of the rabbits. For example, in the Florida Keys over 70% of the marsh rabbits in a study had diet consisting of two grasses (Sporobolus virginicus and Spartinaspartinae), a succulent shrub (Borrichia frutescens), and one tree species (Laguncularia racemosa) (Chapman and Feldhamer, 1982). While the specific species of plant selected by the rabbits can vary based on location, during the winter when green vegetation is scarce marsh rabbits resort to eating bark. When conditions are especially harsh, marsh rabbits will resort to eating their own feces, a process known as coprophagy, in order to retrieve extra nutrients. In addition to the variation in the selection of nutrients, Marsh rabbits are nocturnal in nature and tend to feed only at night. This adaptation can reduce predation upon the species, ultimately increasing survival rate.
Marsh rabbits require specific habitat requirements for a successful and healthy population. In Florida, adult marsh rabbit populations seem to establish their nesting areas/home ranges in small patches of habitat. Generally, the female constructs the nests out of soft grasses and its own fur. In addition, nests are most often found along the water’s edge. This is an important requirement because it allows the rabbits ready access to a water source. In fact, this habitat requirement is so heavily preferred that the rabbits have adapted to have characteristics such as furless feet with long claws. These adaptations lead to the behaviors such as submerging themselves in the water, and only keeping its nose and eyes above the surface. (6) This swimming technique allows the rabbits to escape quickly from predators. Furthermore, the marsh rabbit will find habitat in hollow logs, groups of cattails, grasses, dense thickets and abandoned burrows (6).
The marsh rabbit has two main predators that impact their population, the great-horned owl (Bubo virginianus) and the marsh hawk (Circus cyaneus). Infant and juvenile marsh rabbits are also often prey of the Eastern diamondback rattlesnakes (Crotalus adamanteus) and water moccasins (Agkistrodon piscivorus). Other less common predators include bobcats (Lynx rufus), barn owls (Tyto alba), barred owls (Strix varia), red-tailed hawks (Buteo jamaicensis), bald eagles (Haliaeetus leucocephalus) and red wolves (Canis rufus). While red wolves have only recently been reintroduced, studies have shown that marsh rabbits are the more heavily preyed upon in the areas where the wolves have been reintroduced (Chapman and Willner 1981; Jones, 1997; “Virginia Department of Game and Inland Fisheries, 2007”). Despite the marsh rabbits nocturnal habits, they are still a major food source for other species higher in the trophic level.
Marsh rabbits tend to be hosts to the ticks, fleas, rabbit ticks and warble flies (8). The rabbit tick is said to be the main vector of the disease tularemia but other ticks and fleas can carry the disease. As stated by the Centers for Disease Control and Prevention, tularemia is caused by the bacterium Francisella tularensis. Also, it states this disease is zoonotic, therefore humans are susceptible to infection as well. Transmission can be through direct contact with the flesh or blood of an infected rabbit, even rabbits that are not properly cooked can transmit the disease. Typical symptoms include sudden fever, chills, headaches, diarrhea, joint pain, muscle aches, dry cough and progressive weakness. This disease can even cause the development of pneumonia. Though this disease has only about a 7% fatality rate in humans, tularemia is fatal to rabbits (Chapman and Feldhamer, 1982; 14).
Marsh rabbits are also the host of ticks that carry Rocky Mountain Spotted fever. CDC states this disease is caused by the bacterium Rickettsia rickettsii and can potentially fatal to humans. This bacteria can be transferred into humans through the bite of an infected tick species. Typical symptoms include a fever, headache, abdominal pain, vomiting, and muscle pain. Though absent the first few days, a rash may develop as well. (Chapman and Feldhamer, 1982; Jones, 1997, 14).
The United States Fish and Wildlife Service listed the Lower Keys marsh rabbit subspecies in 1990 as endangered. The current population size has not been estimated, but The United States Fish and Wildlife Service (1999) is currently developing a recovery plan for the subspecies. Since the marsh rabbit’s population has been declining due to habitat loss and fragmentation, it is best to target these areas when developing and implementing a management plan.
There are two different levels that need to be targeted when managing; the species level and the habitat level. For the species level, information is needed on the distribution and status of the marsh rabbit. Specifically, the population of the marsh rabbit needs to be determined and consistently known in order to develop any effective management practice. The best way to gain more information on this subject would be to conduct more aerial and ground surveys that demonstrate a distinct range of the marsh rabbit. In addition, it would be beneficial to conduct absent and present surveys throughout the different seasons to determine when the species occupies certain areas during a specific time. Keeping the marsh rabbit protected under the law will help prevent a decline from human made fragmentation. Lastly for species level management, regulation of poaching, hunting and predation need to be implemented by creating boundaries and limits (13). For example, in South Carolina hunting is controlled by the Department of Natural Resources, where they have a bag limit set of 5 rabbits (6).
Habitat level management should begin with the prevention of degradation of todays’ marsh rabbits habitat. There should be a type of protection and management of the areas that these rabbits are present on. Rules and regulations need to be set for both public and private lands. Also being that the numbers of rabbit habitat sites are relatively low for the Lower Keys subspecies, some sites need to be created or restored. In order to do this information on how a specific habitat affects the survival, distribution and abundance of the marsh rabbit needs to be researched and verified (13).
On both levels, public awareness and installing a stewardship should be done to get the participation of the landowners. The more help from people the more knowledge and effectiveness there will be in managing for this species (13).
Challenges (including climate change)
The marsh rabbit is classified as an endemic species. Thus, meaning this species has “evolved in an environment with reduced levels of competition, predation, and disease, and are thus more susceptible to extinction.” (13) Works Cited
1. Bachman, J., 1837. Description of a new species of hare found in South Carolina. Journal of the Academy of Natural Sciences of Philadelphia, 7:194-199.
2. Bowers, N., Bowers, R.; Kaufman, K. (2007). Kaufman Field Guide to Mammals of North America (12th ed.). Houghton Mifflin Harcourt. p. 26.
3. Centers for Disease Control and Prevention [CDC] < http://www.cdc.gov/>. Accessed 15 Nov 2013.
4. Chapman, J., Feldhamer, G. 1982. Wild Mammals of North America. Baltimore, Maryland, USA: The Johns Hopkins University Press.
5. Chapman, J, A and Willner, Gale. 1981. Sylvilagus palustris. Mammalian Species 153: 1-3.
6. Encyclopedia of Life. Sylvilagus palustrisMarsh Rabbit.