Wetland Habitats for Wildlife of the Chesapeake Bay Matthew C
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..;. Ecology of Wetlands and Associated Sysum.r. Edited by S.K. Majumdar, E.W. Miller and Fred J. Brenner C 1998, The Pennsylvania Academy of Sc:ienc:e. Chapter Twenty-Three WETLAND HABITATS FOR WILDLIFE OF THE CHESAPEAKE BAY MATTHEW C. PERRY Patuxenc Wildlife Research Center Laurel, MD 20708 . : . INTRODUCTION . Early explorers co the Chesapeake Bay were amazed With the seemingly inexhaustible wildlife resources associated with the ~e tl ands of the Bay (1). Although explorers su~h as John Smith were the first to report in writing of these resources. it was some of ¢e traders who.were most descriptive because of their . intense interest and close involvement ih the commercial value of .wildlife. An understanding of the population size of some of the wildlife that thrived in the Bay when the country was first settled can be obtained from .the reports and journals of some of the early explorers and traders. · · One such person was Captain Henry Acct, who was more. of a materialist than explorer and left the Jamestown Colony in 1632 "for the rich country to the north .. (I). In June he travelled to Anacostia (now Washington. D.C. area) along the Pocomac River where he obtained "800 weight of beaver'' (Castor canadensis) (2). In the summer of 1632 he trave ll~d north again to Patobanos (Port Tobacco) where he found 5000 Indians willing to kill beaver and preserve their furs·: He estimated that they would obtain 5-6 thousand pounds of furs- before his ne;"(t trip. in the spring (3). Fleet's ability to deal with the Indians was probably enhanced because he had been a prisoner of theirs in earlier years and was proficient in their language (I). Wetland Habitats for Wildlife of the Chesapeake Bay 333 The wild animals seen by the early explorers of Chesapeake Bay were numerous because of the expansive and fertile wetlands that characterized the Bay. Few areas in the world have supported such tremendous populations of wildlife, and these populations, although now much reduced in numbers, are still one of the reasons the Bay has attracted such attention from nature lovers, scientists, and the public. One· of the factors causing the decline of wildlife populations is the continued loss of natural wetlands (estuarine and palustrine) in the Bay and throughout its watershed. Based on aerial surveys, the greatest losses occurred among the forested wetlands (4). The only wetlands in the Bay watershed that have increased in acreage were human created ponds and these may have limited value to wildlife. The classification of wetlands has received considerable atcencion from many agencies responsible for the regulations established to proted them (5, 6). In this chapter wetlands are broadly grouped into three major categories (shallow-water wetlands, emergent wetlands, and forested wetlands) based mainly on the type of vegetation that dominates the area. This general categorization of wetland tJPes has been selected because of the mobility of wildlife (especially birds), which allows them to traverse several habitats in a s~ort period of time. · In this discussion, shallow-water wetlands ·are those that are mainly open water areas near shore usually with some trpe of submerged aquatic vegetation . (SAY). These wetlands also include mud flats and sand bars often in close association with open water areas. Emergent wetlands are usually found adjacent to shallow-water wetlands and have primarily herbaceous emergenc planes as the dominant vegetation. Forested wetlands are dominated by trees and shrubs, and often are adjacent to emergent wetlands. In this discussion, only minor consider ation is given to specific modifiers of wetlands (water regime, water chemistry, and soil) as described by Tiner and Burke (6). ' This chapter reviews wildlife that use these three generai wetland habitats. Wildlife discussed in this chapter are the species that are most obvious or unique (Table I), and no attempt is made to deal with all specieS .or groups of speCies. Wildlife is grouped into four major categories: birds, mammals, reptiles, ·and amphib ians. Invertebrates and fish are not·considered in this chapter, although it is ·recog nized that they form important components in the stri.icture.of wetland ecosystems . .. ! BIRDS Among the vari9us groups of birds in the Bay area; .waterfowl (swans, geese. and ducks) are probably the most obvious. Swan:; in the Bay· include the tundra swan (Olor columbianus) and the mute sw;in (Cygnus olor), while the geese include the Canada goose (Branra canadensis) and two s~bspecies of the Sf)OW goose (Chen ·caerufescens): :The ducks are comprised of 21 species and are divided inco cwo major types (dabbling and diving) bused on their feeding behavior. Diving ducks completely submerge ~hile feeding, where::is. dabbling ducks jus1 tip-up or dabble in shallow water. · · · 334 Ecology of Wetlands and Associated Systems TABLE l Wildlife Sptcies that art Rtprtstntative of tht lVetla11ds of Chtsaptakt Bay BIRDS Sl1allow-wat1r wetlands: Canv:uback Aythya valisineria Redhead Aythya americana Bald eagle Haliattrus ltucocephalu.s Osprey Pandion haliattus Great blue heron Ardta htrodias Killdeer Charadrius vociftrus Emtrgtnt wetlands: American Black duck Anas rubripts M:i.llard Anas platyrhynchos Northern hnnier ·Circus c:yantus Sora Pof7.arta carolina Red-winged blackbird Agelaiu.s photnictus Marsh wren Cistothorus palustris Forested wetlands: Wood duck Aixsponsa Red-shouldered hawk Butto lintatus Bam:d owl Strix van'a Common yellowthroat Gtochlypis trichas MAMMALS Shallow-water wetlands: No mammal consered endemic to this habitat in the Bay. Emtrgtnt wttl.ands: Muskrat Ondatra r.ibtrhic11s Nutria Myocastor coypus Meadow vole Micorus ptnsylanicus Fornttd wetl.ands:· Beaver · ; · Castor canadtnsis River otter · Lulra canadtnsis . White-footed mouse Peromyscus leucopu.s . ' Delmarva fox squirrel Sciurus niger cinertus REPTILES AND AMPHIBIANS Shailow-wattr wetlands: Diarnondback terr.tpin Malaclemys terrapin Snapping turtle Clielydra strptntina Emtrgtnt wit/ands: Northern wnter snake , . Ntrodia sipedon Painted turtle C~rysemys picta Foresttd wetlands: Wood frog Rana sylvatica Spring peeper Pstudoacris cnicifer M:itbled salamander Ambystoma opac11111 Spotted salamander Amb.vstoma 111ac11lcu11m Wetland Habitats for Wildlife of the Chesapeak4 Bay • 335 Waterfowl that winter on Chesapeake Bay now number less than one million individuals (7), although they once probably ranged from 10-15 million. When waterfowl surveys began in the late 1940s following World War II, there were counts of over 200-400 thousand for several duck species such as the canvasback (Aythya valisineria), greater scaup (A. marila), lesser scaup (A. affinis), and American black duck (Anas rubripes) (8). It is possible that before the commer cial ("market") hunting of waterfowl in the late 1800s (9), that they may have numbered 10 times what they did when surveys began in the late 1940s. Unfortunately, the only record we have of the numbers is the eye-witness accounts of the hunters and naturalists and the reportS of the thousands of birds that went to the markets for over two decades (9). One eye-witness account described the water as black with ducks, that the sound when they took flight was like the rumbling of distanc thunder, and that over one square mile of the sky was covered with ducks at one time ( l ). Raptors (or birds of prey) as a group include the eagles, hawks, and owls and typically feed on animal food, which they obtain by hunting. Because they typi cally are high flying birds that may soar for long periods they can be associated with many habitat types. Some arc resident to the Bay while others just migrate through the Bay area. One biologis·t in 1949 recorded 2214 hawks on migration over a pond near Solomons, Maryland, during a seven-hour period (10). Wading birds (herons and egrets) as a group arc medium- to large-sized birds. Like the raptors, they feed high on the food chain and, therefore, have received attention as species affected by chemical contaminants. Because they nest in large groups they often are referred to as colonial nesting birds (11). Shore birds are represented by the sandpipers and plovers, that feed mainly on invertebrates and seeds in sand or mud substrates. Rails are more secretive than shore birds and usually associated with heavy vegetative cover. Both groups were heavily hunted around the turn· of the century and their numbers were greatly reduced during this penod. Most species are now totally; pro tected by the 1918 Migratory Bird Treaty Act. The Act allows hunting regula: tions to be promulgated each year for some· shorebirds, such as American woodcock (Scolopax minor), common snipe (Gallinago gallinago), and for some rail species. Shallow-water Wetlands The shallow-water wetlands of the Bay proper historically have been important wintering areas for waterfowl ( 12). Some species, such as the tundra swan and the Canada goose, intensively used the.shallow-water wetlands where they fed on SAY (13, 14). During the period between l952 and .1956, the average wintering population of- cundro swans in the Bay constituted nearly half of the continental population and about three-fourths of_the Atlantic coastal population ( 1S) . Populations of Canada geese .were always high in the Bay, bu.t :i.ctually increased when SAY declined. because it contributed to the conversion to :i. com 336 Ecology of Wetlands and Associated-Systems diet that was more beneficial during the winter. With the high energy com diet, geese required less feeding time and therefore less exposure to hunting. Now swans and geese are more frequently observed in agricultural fields where they feed on waste com left from commercial harvest operations or on field cover crops (7, 16). Goose populations reached a high count of over 700,000 in 1981 before declining probably due to overharvest. especially from guided hunting parties, that changed their hunting techniques to take advantage of field feeding by the geese.