Willets--BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

Species	Catoptrophorus semipalmatus is about 38 cm in length, and has a mass of approximately 215 grams (Dunning, 1993). On average, females are somewhat larger than males (Kibbe, 1995). Its body is grayish brown with gray legs and a long straight bill. This species can be distinguished in flight by a black and white wing pattern (Bull and Farrand, 1977). During the winter, the ventral side of the willet is white.
Status in Estuaries	The willet is a solitary nester that breeds in coastal beaches, freshwater and salt marshes, lake shores and wet prairies. It may nest in open areas where vegetation is sparse. A typical nest is a simple depression on open ground or in a grass clump lined with vegetation or bits of shell (Bull and Farrand, 1977). Average clutch contains 4 brown-spotted olive-buff eggs. Young are precocial (Ehrlich et al., 1988).
Abundance and Range	No estimate of the continental willet population is available. The willet breeds locally in southern Canada, U.S. and West Indies, and winters from the southern U.S. to central South America (Bull and Farrand, 1977).
Site Fidelity	This species has separate feeding and nesting territories, and maintains strong fidelity to its feeding territory (Ehrlich et al., 1988).
Ease of Census	Moderate. Willets are very conspicuous (Kibbe, 1995).
Feeding Habits	Generalist. The willet forages in mudflats, intertidal areas, and shallow marsh waters by taking items from the surface or probing the mud with its bill. Both animals and plants are consumed (Kibbe, 1995). Preferences include fiddler crabs, gastropods (Littorina), marine worms, small fish, and vegetable matter.

Willet Contaminant Exposure Data
I.	Organochlorine Contaminants
1.	One South Carolina specimen, collected in 1973, apparently died from nephrosis (Blus and Lamont, 1979). Its brain contained only little DDE (0.2 mg/g wet wt) and PCBs were not detected.
2.	Fifty-five willet carcasses collected in 1986 from Laguna Atascosa NWR, Port Mansfield, South Padre Island, and Bastrop Bayou, Texas were analyzed for DDE and PCBs (Custer and Mitchell, 1991). Mean DDE concentration averaged <1 mg/g wet weight, and the highest value was found in an individual collected from Port Mansfield (2.5 mg/g). PCBs were rarely detected, with the highest value being 1.4 mg/g in an individual from Bastrop Bayou. No other organochlorines were detected.
3.	Willets collected from Delaware Bay in 1989 were analyzed in four composites of five birds each and contained the following mean concentrations of organochlorines (mg/g wet weight): 0.49 DDE, 0.38 total PCBs, 0.51 total DDT, 0.02 total chlordane, and 0.02 dieldrin (Day et al., unpublished data).
II.	Cholinesterase-Inhibiting Pesticides
	No direct exposure data available
III.	Trace Elements, Metals, and Metalloids
1.	In 1977, two willets were collected from the Brunswick Estuary in Georgia (Odom, 1978). Mercury was elevated to a maximum concentration of 6.00 mg/g (units assumed to be wet weight) in the liver and 2.57 mg/g in breast tissue.
2.	In 1982, willets (N=2) collected in Texas were one of six bird species with a feeding habit of probing sediment that did not have ingested Pb shot (Hall and Fisher, 1985).
3.	In 1986, willets were collected at four locations in Texas, and their livers were analyzed for As, Se, and Hg (Custer and Mitchell, 1991). The arithmetic mean (range) As concentration was highest in willets collected from South Padre Island at 7.5 (2.9-11) mg/g dry weight. Selenium was also highest at South Padre Island at 5.6 (3.7-6.4) mg/g. Mercury was highest at Port Mansfield at a geometric mean and range of 3.4 (1.2-17) mg/g.
4.	Willets collected from Delaware Bay in 1989 were analyzed in four composites of five birds each and contained the following mean concentrations of metals (mg/g dry weight): 0.592 Hg, 0.926 As, 9.98 Cu, 78.2 Sr, 89.3 Zn, and 1.24 Ba (Day et al., unpublished data). Lead was found at concentrations <7.0 mg/g, and Ni at <2.50 mg/g.
5.	Sediment ingestion was analyzed in 16 willets collected in 1994 from two locations near San Diego, California: North Island Naval Air Station and Tijuana Slough National Wildlife Refuge (Beyer et al., 1999). Sediment content in digesta was estimated at 3%, much lower than the other shorebird in this study, the black-bellied plover. Concentrations of B, Cd, and Zn in digesta were not correlated with sediment ingestion, implying that exposure to these elements comes mainly form the diet and not from sediment ingestion in this species. The digesta contained high concentrations of Ca, presumably due to a dietary preference for molluscs and crustaceans.
IV.	Petroleum
	No residue data available
Willet Contaminant Response Data
I.	Organochlorine Contaminants
	No response data available
II.	Cholinesterase-Inhibiting Pesticides
1.	Brain cholinesterase activity did not differ among locations on the Lower Rio Grande (Custer and Mitchell, 1991).
III.	Trace Elements, Metals, and Metalloids
	No response data available
IV.	Petroleum
	No response data available
References for the Willet
Beyer, W.N., J. Spann, and D. Day. 1999. Metal and sediment ingestion by dabbling ducks. Sci. Total Environ. 231:235-239.
Blus, L. J. and T. G. Lamont. 1979. Organochlorine residues in 6 species of estuarine birds South Carolina USA 1971-1975. Pest. Monitor. J. 13:56-60.
Bull, J. and J. Farrand, Jr. 1977. The Audubon Society Field Guide to North American Birds. Alfred A. Knopf, New York.
Custer, T.W. and C.A. Mitchell. 1991. Contaminant exposure of willets feeding in agricultural drainages of the lower Rio Grande Valley of south Texas. Environ. Monit. Assess. 16:189-200.
Day, C.G., M.T. Chezik, and T. Augspurger. 1991. Environmental contaminants in the prey of Delware Bay peregrine falcons (Falco peregrinus). U.S. Fish and Wildlife Service. 20 pp.
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 Birder=s Handbook. Simon & Schuster, New York. 785 pp.
Hall, S.L. and F.M. Fisher Jr. 1985. Lead concentrations in tissues of marsh birds: relationship of feeding habits and grit preferences to spent shot ingestion. Bull. Environ. Contam. Toxicol. 35:1-8.
Kibbe, D.P. 1995. Willet. In L.E. Dove and R.M. Nyman, eds., Living Resources of the Delaware Estuary. The Delaware Estuary Program. pp. 465-467.
Odom, R.R. 1978. Statewide wildlife investigations: Mercury contamination studies. Georgia Game and Fish Div. 15 pp