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BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

Black Skimmer Black Skimmer photo by Jim Zingo
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Biological Characteristics

Species Rynchops niger is approximately 46 cm in length. Males tend to have a greater average mass (349 grams) than females (254 grams) (Dunning, 1993). Its dorsal side is black and its ventral side is white. The most conspicuous characteristic is its laterally flattened red bill. The lower mandible of the bill is about 1/3 longer than the upper mandible (Bull and Farrand, 1977). The male is substantially larger than the female (Burger and Gochfeld, 1992). Sexes can also be distinguished by the longer lower mandible and longer wing cord of the male (Erwin, 1977).
Status in Estuaries The black skimmer is a colonial species that often nests with other tern species (Hoopes et al., 1994). Breeding and foraging occurs in estuaries, with nests typically constructed on open spaces in beaches, salt marshes and dredge spoil islands. Nests are not elaborate; usually just a simple surface scrape. Typical clutch size is 4 eggs; maximum is 5 (Erwin, 1977). Young are semiprecocial (Ehrlich et al., 1988). The maximum lifespan recorded in nature is 20 years (Clapp et al., 1983).
Abundance and Range Breeding range extends from Massachusetts and Long Island south through the coast of Florida. In winter months, this species can be found as far north as the Carolinas (Bull and Farrand, 1977). About 13,738 individuals were counted along the Atlantic Coast in the late 1970s (Spendelow and Patton, 1984).
Site Fidelity When reproductive success is high, this species often returns to the same location to nest, opting for alternate sites when reproduction has been poor (Erwin, 1977).
Ease of Census Simple
Feeding Habits As their name implies, this species obtains food by immersing its lower mandible into the water and skimming along the surface, allowing night time foraging (Burger and Gochfeld, 1990). Fish are the predominant food item brought to chicks. Species preferences include silversides and killifish. Less common items observed were bay anchovy, mullet, spot, and bluefish (Erwin, 1977).

Black Skimmer Contaminant Exposure Data

I.

Organochlorine Contaminants

A.

Concentrations in Adults

1.

In 1973 and 1974, five black skimmers were found dead: four from Big Pine Key, Florida, and one from Cape Island, South Carolina (Blus and Stafford, 1980). DDE ranged from 0.97- 21.12 g/g wet weight in carcass and from 1.07- 32.80 g/g in brain. Dieldrin, oxychlordane, cis-chlordane, mirex, and toxaphene were <1 g/g in the five carcass and brain samples. PCBs ranged from 2.5-16.9 g/g in carcass, and from 3.2 g/g-32.0 g/g in brain.

2.

In 1983, 15 black skimmers were collected from Chachalacas, Veracruz, Mexico and 15 from Port Mansfield, Texas (White et al., 1985). The geometric mean (range) for DDE in carcasses was 2.5 (1-12) g/g wet weight in Texas and 2.0 (0.8-10) g/g in Veracruz. The geometric mean (range) for PCBs was 1.6 (<10) g/g in Texas and 1.0 (<16) g/g in Veracruz.

3.

From 1980 to 1982, 30 black skimmers were collected from Galveston Bay, Texas (King and Krynitsky, 1986). Mean DDE concentrations ranged from 2.32 g/g wet weight (1981) to 6.54 g/g (1980).  Mean PCB concentrations ranged from 2.29 g/g (1981) to 5.47 g/g (1980).  Dieldrin, chlordane isomers, heptachlor epoxide, and polychlorinated styrenes were detected in less than half the samples, and DDE and HCB were not detected.

B.

Concentrations in Eggs and Embryos

1.

In 1969, and from 1971 to 1975, eggs were collected from the Cape Romain National Wildlife Refuge and other nearby nesting areas located in South Carolina (Blus and Stafford, 1980). DDE was highest in 1974, at a geometric mean concentration of 2.10 g/g wet weight. The highest concentration of mirex was 2.62 g/g in an egg collected in 1969. Dieldrin, oxychlordane, and trans-nonachlor concentrations were consistently <1 g/g. Concentration of PCBs increased to a maximum of 3.9 g/g in 1974.

2.

In 1970, five black skimmer eggs collected from coastal Texas contained DDT at a concentration of 9.68 g/g wet weight, and PCBs at 5.40 g/g PCBs, but dieldrin was not detected (King et al., 1978).

3.

Two black skimmer eggs collected in 1972 along the west coast of Florida contained mean concentrations of 4.50 g/g dry weight DDE, 2.10 g/g PCB, and 0.15 g/g dieldrin (Lincer and Salkind, 1973).

4.

Black skimmer eggs were collected from Corpus Christi, Texas from 1978 to1981, and from Port Mansfield and Laguna Vista, Texas from 1979 to 1981 (White et al., 1984). The geometric mean (range) concentrations for DDE and PCBs were highest in eggs collected from Corpus Christi in 1978 at 11.5 (1.9-43) and 7.2 (4.3-12) g/g g/g wet weight, respectively.

5.

From 1980 to 1982, black skimmer eggs were collected from Galveston Bay, Texas (King and Krynitsky, 1986). The geometric mean (range) for DDE was highest in 1980 at 3.25 (0.5-86) g/g wet weight. Dieldrin, chlordane, HCB, PCS, and heptachlor epoxide were detected at concentrations <1 g/g. Concentration of PCBs were highest in 1980 at 4.18 (2.4-10) g/g.

6.

In 1984, 53 eggs were collected from Laguna Vista, Texas (Custer and Mitchell, 1987). Geometric mean concentrations of DDE and PCBs were 3.2 and 0.7 g/g, respectively. Only 4% of the eggs tested in 1984 had DDE levels 10 g/g. This was a significant decrease in DDE concentration compared to eggs collected in 1979, 1980, and 1981 during which time 32%- 60% of the eggs tested had 10 g/g.

7.

DDE and PCB concentrations in eggs collected from skimmers nesting in Lavaca Bay and Laguna Vista, Texas were measured in 1984 (King et al., 1991). DDE concentrations did not differ significantly between the two sites, occurring at a geometric mean of 3.4 and 3.2 g/g wet weight, respectively. PCBs were significantly higher a Lavaca Bay, 1.3 g/g, than at Laguna Vista, 0.8 g/g.

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

A.

Concentrations in Adults

1.

In 1973, two black skimmers were collected from Big Pine Key, Florida and their livers analyzed for metals (Blus and Stafford, 1980). Mercury concentrations were highest at 8.5 g/g fresh weight, Cu at 10.7 g/g, Zn at 42.0 g/g, and Pb at <0.1 g/g.

2.

In 1980 and 1981, black skimmers were collected from Galveston Bay, Texas (King and Cromartie, 1986). Mercury in the liver occurred at a geometric mean (range) of 1.06 (0.5-2.7) and 1.42 (0.6-16) g/g wet weight in 1980 and 1981, respectively. Lead in the liver ranged from 0.1-0.4 g/g in 1980 and 0.1-0.2 g/g in 1981. Cadmium in the kidney was 1.65 (0.7-4.1) g/g in 1980 and 1.93 (0.8-7.5) g/g in 1981. Selenium in the kidney was 2.97 (1.3-8.2) g/g in 1980 and 2.44 (1.3-5.2) g/g in 1981.

3.

Metals were measured in breast feathers of male and female skimmers nesting on Cedar Beach in Long Island, New York (Burger and Gochfeld, 1992). The geometric mean concentrations of Pb (1480 ng/g dry weight) and Cd (48 ng/g) were significantly higher in females, which have a smaller body size. Although not statistically significant, levels of Hg (13,080 ng/g), Cr (10350 ng/g), Mn (2455 ng/g), and Cu (28,080 ng/g) tended to be higher in females.

4.

Breast feathers collected in 1989 from Cedar Beach, Long Island, New York were analyzed for Pb concentrations (Burger et al., 1994). Concentrations ranged from approximately 100-2000 ng/g in fledglings and 700-3300 in adults.

5.

In 1989, feathers collected from fledglings nesting in the New York Bight had geometric mean metal concentrations of 982-1816 ng/g dry weight Pb and 33-105 ng/g Cd (Burger and Gochfeld, 1993).

6.

When examining the accumulation of Pb and Cd in feathers, no significant difference was found between black and white feathers of skimmers (Gochfeld et al., 1991).

B.

Concentrations in Eggs, Embryos, and Nestlings

1.

In 1984, black skimmer eggs were collected from Lavaca Bay (N=43) and Laguna Vista (N=9), Texas (King et al., 1991). Mean concentrations of Hg (0.46 g/g wet weight) and Se (0.75 g/g) were significantly higher at Lavaca Bay.

2.

In 1989, eggs were collected from skimmers breeding in Middle Sedge and Tow, New Jersey (Burger and Gochfeld, 1993). Lead levels were low, with geometric mean concentrations of 411 ng/g dry weight at Middle Sedge and 297 ng/g at Tow. Mean Cd concentration was 4 ng/g at Middle Sedge and 3 ng/g at Tow.

3.

Mercury was determined in breast feathers of black skimmer nestlings and eggs from the New York Bight (Burger and Gochfeld, 1997). Mean concentrations in nestling feathers in 1990 were approximately 3.5 g/g dry weight in samples collected from Tow Island, New Jersey, and, in 1991, 5.0 g/g from Barnegat Light, New Jersey and 3.5 from West Ham, New Jersey. Eggs from Cedar Beach, New York, had an approximate mean concentration of 1.6 g/g.

IV.

Petroleum

1.

From 1970 to 1978, skimmers were observed for external oiling at Cedar and West End Beaches in New York (Gochfeld, 1979). Overall, 1% of the 3936 skimmers observed had some type of oiling. 

Black Skimmer Contaminant Response Data

I.

Organochlorine Contaminants

1.

From 1969 to1975, eggshell thickness was measured in samples collected from South Carolina (Blus and Stafford, 1980). The percent change in thickness compared to pre-1947 values ranged from a 5.2% decrease in thickness in 1969 to a 4.8% increase in thickness in 1971. Between 1969 and 1975, no significant difference in mean eggshell thickness was detected.

2.

Shell thinning was measured in black skimmer eggs collected from the Coast of Texas in 1970 (King et al., 1978). A 4% decrease in shell thickness was documented when the 1970 values (0.240 mm) were compared to pre-1943 values (0.249 mm).

3.

The thickness of eggs collected from Corpus Christi, Port Mansfield, and Laguna Vista, Texas from 1978 to 1981 was compared to eggs collected along the coast of Texas between 1882 and 1930 (White et al., 1984). Eggshell thickness decreased in the latter collection by 4% to 12% except for Corpus Christi samples collected in 1980.

4.

Between 1970 and 1990, there was a 49% increase in the thickness (0.366 mm - 0.546 mm) of black skimmer eggs collected from Long Island, New York (Burger et al., 1995). From 1980 to 1990 there was a 22% increase in the thickness of eggs (0.351 mm - 0.428 mm) collected from Barnegat Bay, New Jersey.

5.

In 1980 to 1982, eggs were collected from Galveston Bay, Texas and shell thickness was compared to pre-1947 values (King and Krynitsky, 1986). The greatest decrease in shell thickness (6%) was seen in 1980.

6.

Black skimmer eggs collected in 1984 from Laguna Vista and Lavaca Bay were significantly thinner (0.24 mm) than pre-1943 values (0.25 mm) (King et al., 1991). No correlation was found between shell thickness and DDE concentration. The concentration of DDE was significantly higher (7.0 g/g wet weight) at sites where no eggs hatched compared to those where some eggs hatched (3.2 g/g) and those where all eggs hatched (2.4 g/g). The concentration of Hg, Se, DDE, and PCBs was not related to nesting success.

7.

In 1984, 82 young survived to 21 days of age of the 323 black skimmer eggs laid on the southern coast of Texas (Custer and Mitchell, 1987). DDE concentration was found to be related to nest success in that all eggs hatched when DDE concentration averaged 1.9 g/g, whereas here no eggs hatched when DDE concentration averaged 5.9 g/g. No relationship was found between DDE concentration and eggshell thickness.

II.

Cholinesterase-Inhibiting Pesticides

 

No response data available

III.

Trace Elements, Metals, and Metalloids

 

No response data available

IV.

Petroleum

 

No response data available 

 

References for Black Skimmer

Blus, L.J., and C.J. Stafford. 1980. Breeding biology and relation of pollutants to black skimmers and gull-billed terns in South Carolina. Special Scientific Report--Wildlife number 230. Fish and Wildlife Service, Washington, D.C.

Bull, J. and J. Farrand Jr. 1977. The Audubon Society Field Guide to North American Birds. Alfred A. Knopf, New York. 784 pp.

Burger, J., and M. Gochfeld. 1990. The Black Skimmer Social Dynamics of a Colonial Species. Columbia University Press, New York. 355 pp.

Burger, J., and M. Gochfeld. 1992. Heavy metal and selenium concentrations in black skimmers (Rynchops niger): gender differences. Arch. Environ. Contam. Toxicol 23:431-434.

Burger, J., and M. Gochfeld. 1993. Lead and cadmium accumulation in eggs and fledgling seabirds in the New York Bight. Environ. Toxicol. Chem. 12:261-267.

Burger, J., and M. Gochfeld. 1997. Risk, mercury levels, and birds: Relating adverse laboratory effects to field biomonitoring. Environ. Res. 75:160-172.

Burger, J., M.H. Lavery, and M. Gochfeld. 1994. Temporal changes in lead levels in common tern feathers in New York and relationship of field levels to adverse effects in the laboratory. Environ. Toxicol. Chem. 13:581-586.

Burger, J., K. Viscido, and M. Gochfeld. 1995. Eggshell thickness in marine birds in the New York Bight--1970s to 1990s. Arch. Environ. Contam. Toxicol 29:187-191.

Clapp, R.B., D. Morgan-Jacobs, and R.C. Banks. 1983. Marine birds of the southeastern United States and Gulf of Mexico. Part III: Charadriiformes. U.S. Fish and Wildlife Service, Office of Biological Services, Washington, D.C. FWS/OBS-83/30. 853 pp.

Custer, T.W., and C.A. Mitchell. 1987. Organochlorine contaminants and reproductive success of black skimmers in South Texas, 1984. J. Field Ornith. 58:480-489.

Dunning, Jr., J.B., ed. 1993. CRC Handbook of Avian Body Masses. CRC Press, Ann Arbor. 371 pp.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The Birders Handbook. Simon & Schuster, New York. 785 pp.

Erwin, R.M. 1977. Black skimmer breeding ecology and behavior. Auk 94:709-717.

Gochfeld, M. 1979. Prevalence of oiled plumage of terns and skimmers on Western Long Island, New York: baseline data prior to petroleum exploration. Environ. Pollut. 20:123-129.

Gochfeld, M., J. Saliva, F. Lesser, T.Shukla, D. Bertrand., and J. Burger. 1991. Effects of color on cadmium and lead levels in avain contour feathers. Arch. Environ. Contam. Toxicol. 20:523-526.

Hoopes, E.M., P.M. Cavanagh, C.R. Griffin, and J.T. Finn. 1994. Synthesis of information on marine and coastal birds of the Atlantic Coast: Abundance, distribution, and potential risks from oil and gas activities. Volume II: Species accounts, abundance, distribution, and status. Massachusetts Cooperative Fish and Wildlife Research Unit, Amherst, Massachusetts. 178 pp.

King, K.A., and E. Cromartie. 1986. Mercury, cadmium, lead, and selenium in three waterbird species nesting in Galveston Bay, Texas, USA. Colon. Waterbirds 9:90-94.

King, K.A., and A.J. Krynitsky. 1986. Population trends, reproductive success, and organochlorine chemical contaminants in waterbirds nesting in Galveston Bay, Texas. Arch. Environ. Contam. Toxicol 15:367-376.

King, K.A., E.L. Flickinger, and H.H. Hildebrand. 1978. Shell thinning and pesticide resdiues in Texas aquatic bird eggs, 1970. Pestic. Monit. J. 12:16-21.

King, K.A., T.W. Custer, and J.S. Quinn. 1991. Effects of mercury, selenium and organochlorine contaminats on reproduction of Forsters terns and black skimmers nesting in a contaminated Texas bay. Arch. Environ. Contam. Toxicol. 20:32-40.

Lincer, J.L., and D. Salkind. 1973. A preliminary note on organochlorine residues in the eggs of fish-eating birds of the west coast of Florida. Florida Field-Nat. 1: 19-22.

Spendelow, J.A., and S.R. Patton. 1988. National atlas of coastal waterbird colonies in the contiguous United States: 1976-82. Biological Report 88(5). U.S. Fish and Wildlife Service, Washington, D.C.

White, D.H., C.A. Mitchell, and D.M. Swineford. 1984. Reproductive success of black skimmers in Texas relative to environmental pollutants. J. Field Ornith. 55:18-30.

White D.H., C.A. Mitchell, and C.J. Stafford. 1985. Organochlorine concentrations, whole body weights, and lipid content of black skimmers wintering in Mexico and in South Texas, 1983. Bull Environ. Contam. Toxicol. 34:513-517.

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