Bombay Hook National Wildlife Refuge

Site Description

  • State: Delaware
  • County: Kent
  • Ownership: Federal


  • Bear Swamp Pool: 226 acres
  • Finis Pool: 121 acres
  • Raymond Pool: 95 acres
  • Shearness Pool: 458 acres

Ecology and Management

Great Egret, Bombay Hook National Wildlife Refuge, Delaware. Photo credit: Mike Carlo/USFWS

The impoundments at Bombay Hook National Wildlife Refuge are nationally known birding hotspots, especially for shorebirds, waterfowl, and wading birds. Bombay Hook NWR has been designated a Ramsar Wetland of International Importance as well as a Globally Important Bird Area. U.S. Fish and Wildlife lists 278 birds that use the wider refuge and eBird reports counts of 239 species at Raymond Pool, 219 species at Shearness Pool, 226 species at Bear Swamp, and 178 species at Finis Pool. Raymond Pool hosts especially impressive numbers of shorebirds and waterfowl with high counts of 10,100 Dunlin; 7,000 Semipalmated Sandpiper; nad 4,890 Short-billed Dowitcher.

The impoundments at Bombay Hook NWR are managed under a moist soil management regime with water levels are drawn down in the spring to provide mudflats for migrating shorebirds. This permits the germination and growth of lush vegetation, and wading birds feed on fish in the pools that form. The impoundments are then flooded in the fall to give dabbling ducks access to the seeds of the wetland plants. In the spring the cycle begins again. Invasive Common Reed (Phragmites australis) has been an ongoing challenge in maintaining the productivity of the impoundments.


Most of the impoundments at Bombay Hook NWR are sheltered by vegetated marsh but still experience occasional overtopping. Shearness Pool is exposed to higher wave energy due to the fact that it borders a large unvegetated intertidal flat. While Bombay Hook has not experienced any failures of their imoundments they are subject to occasional overwash and occasional cave-ins due to localized muskrat activity.

Human Value

Bombay Hook NWR receives approximately 110,000 visitors every year and is the most popular birding site in the State of Delaware. Bombay Hook staff, lead a variety of environmental education and interpretation programs each year for local schools and collaborate on research with the University of Delaware and Delaware State University.

Literature Resources

Below is a list of articles describing research occurring at or near the impoundments:
  • Anderson, J. T. 2006. Evaluating competing models for predicting seed mass of Walter’s millet. Wildlife Society Bulletin 34:156-158.
  • Breese, G., K. Kalasz, J. Lyons, C. Boal, J. Clark, M. DiBona, R. Hossler, B. Jones, B. Meadows, M. Stroeh, B. Wilson, and M. Runge. Structured decision making for coastal managed wetlands in Delaware. Shepherdstown, West Virginia: United States Fish and Wildlife Service, National Conservation Training Center; 2010.
  • Chamberlain, E. B. A survey of the marshes of Delaware. Dover, Delaware: The State of Delaware, Board of Game and Fish Commissioners; 1951.
  • Chan, S., and S. Shulte. A Plan for Monitoring Shorebirds During the Non-breeding Season in Bird Monitoring Region Delaware – BCR 30. Manomet, Massachusetts: Manomet Center for Conservation Sciences; 2003.
  • Conroy, M. J., G. R. Costanzo, and D. B. Stotts. 1989. Winter survival of female American black ducks on the Atlantic coast. The Journal of Wildlife Management 53:99-109.
  • Detterline, J., and W. Wilhelm. 1991. Survey of pathogenic Naegleria fowleri and thermotolerant amebas in federal recreational waters. Transactions of the American Microscopical Society 110:244-261.
  • Erwin, R. M., D. K. Dawson, D. B. Stotts, L. S. McAllister, and P. H. Geissler. 1991. Open marsh water management in the mid-Atlantic region: aerial surveys of waterbird use. Wetlands 11:209-228.
  • Green, A., J. Lyons, M. Runge, W. Kendall, H. Laskowski, S. Lor, and S. Guiteras. Timing of impoundment drawdowns and impact on waterbird, invertebrate, and vegetation communities within managed wetlands, Study manual – Final version field season 2007. Laurel, Maryland: USGS Patuxent Wildlife Research Center; 2007.
  • Green, A. W., W. L. Kendall, H. P. Laskowski, J. E. Lyons, L. Socheata, and M. C. Runge. Draft version of the USFWS R3/R5 Regional Impoundment Study. Washington, D. C.: U. S. Fish and Wildlife Service; 2008.
  • Griffith, R. 1946. Nesting of Gadwall and Shoveller on the Middle Atlantic Coast. The Auk 63:436-438.
  • Harding, J. J. 1980. Birding the Delaware Valley Region: A Comprehensive Guide to Birdwatching in Southeastern Pennsylvania, Central and Southern New Jersey, and Northcentral Delaware. Temple University Press, Philadelphia, Pennsylvania.
  • Hill, M. R., and R. B. Frederick. 1997. Winter movements and habitat use by greater snow geese. The Journal of Wildlife Management 61:1213-1221.
  • IWMM [Integrated Waterbird Management and Monitoring Project]. Project Update – October 2010. http://iwmmprogram.ning.com/: Integrated Waterbird Management and Monitoring Project; 2010.
  • Lunt, D. C. 1986. Taylors Gut: In the Delaware State. Middle Atlantic Press, Wilmington, Delaware.
  • Mather, T. Nitrogen and phosphorous analysis of Raymond and Shearness impoundments, Bombay Hook NWR, Summer 1979.
  • Unpubl. Report. Newark, Delaware: Dept.of Entomology and Applied Ecology, Univ.of Delaware; 1979.
  • Mathis, W. N., and T. Zatwarnicki. 2010. New Species and Taxonomic Clarifications for Shore Flies from the Delmarva States (Diptera: Ephydridae). Proceedings of the Entomological Society of Washington 112:97-128.
  • Anonymous. Effects of open marsh water management (OMWM) on bird populations of a Delaware tidal marsh, and OMWM’s use in waterbird habitat restoration and enhancement. Waterfowl and wetlands symposium: proceedings of a symposium on waterfowl and wetlands management in the coastal zone of the Atlantic Flyway. Delaware Coastal Management Program, Delaware Department of Natural Resources and Environmental Control, Dover, DE; 1987. 298 p.
  • Murphey, F. J., and P. P. Burbutis. 1967. Straw Infusion Attractiveness to Gravid Female Culex salinarius. Journal of Economic Entomology 60:156-161.
  • Murray, M. 2014. Delaware gets millions to help beaches, wetlands. Delaware Online June 8, 2014:1.
  • Murray, M., and J. Montgomery. 2012. Marsh impoundments create questions on future responses by state officials. Delaware Online October 23, 2012:1.
  • Philipp, K. R. 2005. History of Delaware and New Jersey salt marsh restoration sites. Ecological Engineering 25:214-230.
  • Pinkney, A. E., P. C. McGowan, D. R. Murphy, T. P. Lowe, D. W. Sparling, and L. C. Ferrington. 2000. Effects of the mosquito larvicides temephos and methoprene on insect populations in experimental ponds. Environmental Toxicology and Chemistry 19:678-684.
  • Wayne, W. J., and T. E. Roberts. 1972. The Summer Scene. The Delmarva Ornithologist 7:4-6.
  • Wilson, B., D. Siok, C. Pinkerton, K. Smith, and B. Scarborough. Evaluating the Evolution of Natural Tidal and Managed Wetlands in Delaware. A presentation given at DE Wetlands Conference. Dover, Delaware: Delaware National Estuarine Research Reserve; 2012.