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BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

 Mottled Duck

Photo of Mottled Duck by Grady Allen, courtesy of Florida Fish and Wildlife Commission
Photo by Grady Allen, courtesy of 
Florida Fish and Wildlife Commission

For more information about Mottled Ducks, click photo to go to the Patuxent Bird ID InfoCenter 



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Biological Characteristics

Species

Anas fulvigua is 22 inches in length, with a wingspan of 30 inches, and a mass of approximately 1,000 grams (males typical greater than females) (Sibley, 2000) .  These ducks have a dark body, white underwings, and an unstreaked buffy throat (Sibley, 2001).  They are darker than mallards, and paler than American black ducks (Sibley, 2000).  Though lacking the extreme sexual dichromatism found in other dabbling ducks, they can be distinguished by bill color; males with brilliant solid yellow bills and females with blotched dull orange or yellow bills (Sibley, 2001 ; Peterson, 1980 ; Beckwith and Hosford, 1957 ). 

Status in Estuaries

Mottled ducks are permanent residents.  They are generally solitary breeders and form pair bonds that may last for life (Sibley, 2001).  Breeding generally occurs in March (Beckwith and Hosford, 1957) .  Small flocks (up to 50 birds) can be observed from the fall through spring (Beckwith and Hosford, 1957) .  Nesting near water in a shallow bowl of grasses and reeds lined with feathers, 8-12 white to pale olive colored eggs are layed, which the female incubates (Kaufman, 1996) . Young are precocial.  The maximum recorded age of this duck was 13 years and 5 months. 

Abundance and Range

Mottled ducks are found along the Atlantic and Gulf coasts from Mexico to South Carolina (Sibley, 2000).  They will utilize any marsh or pond, but prefer brackish ponds near salt marshes (Sibley, 2000; Kaufman, 1996).  They favor treeless marshes, prairies and rice fields (Kaufman, 1996).  Habitat destruction and interbreeding with feral mallards present threats to the population (Kaufman, 1996).  Census in March 2000 by Florida Fish and Wildlife Conservation Commission estimated 11,376 in a 13,338 sq km portion of their Florida range.

Site Fidelity

Mottled ducks are non-migratory, remaining in the southeastern United States year round, sometimes forming flocks in the fall and traveling short distances to better food sources (Sibley, 2001). 

Ease of Census

Moderate; this species is solitary and nests in dense vegetation, though nesting areas are accessible.  They may be confused with the female mallard or the American black duck. 

Feeding Habits

Juveniles often dive to feed on insects, while adults feed on seeds of aquatic plants and grasses, insects, snails, and fish, generally by dabbling in mud near the surface (Kaufman, 1996).  Mottled ducks in the Florida region have been found to feed on at least 77 different species of plants in 51 genera, with the dominant species varying by year and season (Beckwith and Hosford, 1957) .


Mottled Duck Contaminant Exposure Data

I.

Organochlorine Contaminants

1.

One mottled duck was collected in August 1995 from Purvis Creek, Georgia near the site of a former chloralkali facility (Kannan et al., 1998).  Concentrations of organochlorines in breast muscle were: 135 g/g lipid weight PCB, 4.4 ng/g wet weight total DDT, and <1 g/g total chlordane isomers, <0.7 g/g HCH isomers, and <0.6 g/g HCB.  Concentrations of detectable PCB congeners ranged from 3.1 ng/g PCB 195 to 360 ng/g PCB 206.

2.

One mottled duck was collected in the summer of 1995 from Purvis Creek, Georgia near the site of a former chloralkali facility (Kannan et al., 1999).  Concentrations of organochlorines in muscle were 89.5g/g lipid weight PCB, 0.23 g/g total DDT, and 0.002 g/g total chlordane isomers.  HCH isomers, HCB, and PCDDs/PCDFs were not detected.

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available.

III.

Trace Elements, Metals, and Metalloids

1.

Of 144 mottled duck gizzards collected from the northwest corner of Lake Okeechobee, Florida, in 1953 and 1954 14 contained Pb shot (Beckwith and Hosford, 1957) .

2.

In August, 1980, mottled ducks (N=20) were collected from a settling basin in a phosphate mine complex near Bartow, Florida, and from a freshwater marsh (N=10) on the northwest shore of Lake Okeechobee, Florida (Montalbano et al., 1983).  Mean (range) concentrations (ug/g wet weight) of trace elements and metals in the settling basin and marsh, respectively, were: 0.251 (0.070-0.690) and 0.082 (0.073-0.091) Pb, 8.7 (6.5-12.0) and 16.5 (10.0-23.0) Ba, 0.71 (0.67-0.77) and 0.79 (0.75-0.83) As, and 0.026 (0.025-0.028) and 0.026 (0.026-0.026) F.  

3.

During the 1987-1988 hunting season, wing bones (humerus, N=191) were collected from Texas, Louisiana, and Florida (Merchant et al., 1991).  Mean Pb in wing bones (N), and ranges (ug/g dry weight) were as follows:  McFaddin National Wildlife Refuge, Texas, 41.5 (43), 1.7-220; Murphree Wildlife Management Area, Texas, 50.6 (43), 14-170; Anahuac National Wildlife Refuge, Texas, 88.9 (14), 3.0-360; St. Bernard, Louisiana, 27.9 (47), 2.8-160; Lacassine National Wildlife Refuge, Louisiana, 36.0 (70), 1.1-210; Okeechobee, Florida, 33.6 (21), 0.8-190.  Males from Anahuac National Wildlife Refuge had significantly higher Pb than other males or females; females from Anahuac National Wildlife Refuge had significantly lower Pb than females from some other locations; males from St. Bernard had significantly lower Pb than all other males. 

IV.

Petroleum

 

No residue data available.

V.

Other

1.

In August, 1980, mottled ducks (N=20) were collected from a settling basin in a phosphate mine complex near Bartow, Florida, and from a freshwater marsh (n=10) on the northwest shore of Lake Okeechobee, Florida (Montalbano et al., 1983).  Radium 226 concentrations were not different between ages or sexes.  Mean Ra-226 for the marsh was 0.86 pCi/kg, and for the settling basin 3.08 pCi/kg. Radium 226 was significantly higher in ducks from the settling basin than in those from the marsh. 

2.

Mottled ducks were collected from settling ponds on the Noralyn and Clear Springs phosphate mines and on Fort Green and Payne Creek phosphate mines, and from Lake Kissimmee, in central Florida (Myers et al., 1989) .  Pectoral muscles and bone samples.  Mean (range) Ra-226 in bone was 5.9 (3.3-9.6) Bq/kg fresh weight from unmined wetlands, and 62.9 (31.5-128) Bq/kg from mined wetlands.  Mean Ra-226 in muscle was 0.18 Bq/kg from unmined wetlands and 0.22 Bq/kg from mined wetlands. 

3.

One mottled duck was collected in the summer of 1995 from Purvis Creek, Georgia near the site of a former chloralkali facility (Kannan et al., 1999).  Concentrations of organohalogens--extractable organic chlorine (EOCl), extractable organic bromine (EOBr), and extractable organic iodine (EOI)--were measured in the muscle.  Concentrations were 23 g/g wet weight EOCl, and 0.17 g/g EOBrEOI was not detected.


Mottled Duck Contaminant Response Data

I.

Organochlorine Contaminants

 

No response data available.

II.

Cholinesterase-Inhibiting Pesticides

1.

In May of 1982, four mottled ducks were found dead from intentional poisoning with rice seed treated with monocrotophos or dicrotophos in southwestern Matagorda County, Texas (Flickinger et al., 1984) .

III.

Trace Elements, Metals, and Metalloids

 

No response data available.

IV.

Petroleum

 

No response data available. 


References for Mottled Duck

Beckwith, S.L. and H.J. Hosford.  1957.  A report on seasonal food habits and life history notes of the Florida duck in the vicinity of lake Okeechobee, Glades County, Florida.  Amer. Midl. Nat. 57:461-473.

Flickinger, E.L., D.H. White, C.A. Mitchell, and T.G. Lamont. 1984. Monocrotophos and dicrotophos residues in birds as a result of misuse of organophosphates in Matagorda County Texas USA. J. Assoc. Official Anal. Chem. 67:827-828.

Kannan K., H. Nakata, R. Stafford, G.R. Masson, S. Tanabe, and J.P. Giesy.  1998.  Bioaccumulation and toxic potential of extremely hydrophobic polychlorinated biphenyl congeners in biota collected at a Superfund site contaminated with Aroclor 1268. Environ. Sci. Tech. 32:1214-1221.

Kannan K., M. Kawano, Y. Kashima, M. Matsui, and J.P. Giesy.  1999.  Extractable organohalogens (EOX) in sediment and biota collected at an estuarine marsh near a former chloralkali facility.  Environ. Sci. Tech. 33:1004-1008.

Kaufman, K.  1996.  Lives of North American Birds.  Houghton Mifflin Company, New York.

Merchant, M.E., S.S. Shukla, and H.A. Akers.  1991.  Lead concentrations in wing bones of the mottled duck.  Environ. Toxicol. Chem. 10:1503-1507. 

Myers, O.B., W.R. Marion, T.E. O' Meara, and C.E. Roessler.  1989.  Radium-226 in wetland birds from Florida USA phosphate mines. J. Wildl. Manage. 53:1110-1116.

Montalbano, F., J.E. Thul, and W.E. Bolch. 1983.  Radium-226 and trace elements in mottled ducks. J. Wildl. Manage. 47: 327-333.

Peterson, R.T.  1980.  A Field Guide to the Birds, Fourth Edn.  Houghton Mifflin Company, New York.

Sibley, D.A.  2000.  The Sibley Guide to Birds.  Alfred A. Knopf, New York.

Sibley, D.A.  2001.  The Sibley Guide to Bird Life & Behavior.  Alfred A. Knopf, New York.

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