The Ecology of coastal Marshes of Western Lake Erie: A Community ...

found that preferred natural foods ofdiving ducks, such as wild celery,appeared to be more adversely affected byturbidity and stltatlon than foods ofdabbling ducks and geese.The wintering areas for ducks, geese,swans, coots, and other waterfowl havebeen mapped in detaf 1 by Be1 1 rose ( 19761.The Rockefeller Refuge In southwestLouisiana is a well-known wintering areafor migratory waterfowl which cross theGreat Lakes. Like the concentrationareas, qua1 ity wintering habitat mustprovide abundant food and protect ion fromwaves and human disturbance. Over theyears, certain waterfowl, particul arl yCanada geese, have modified thei rwintering activity by stopping at sitessomewhat north of their former winterareas. In general, most stateconservation agencies do not encourage thecreation of resident wintering flocks,particularly in the Lake Erie region,because of the problem of waterfowlstarvation during severe winters.Waterfowl that reach the sprlng breedinggrounds in good condition tend to exhibitgreater nesting success than those whichare undernourished.W1iBQdlL;hlrThese ducks are socalled because they normally do not divebelow the water for food, but merelydabble on the bottom in shallow water.Annually about 17,500,000 mallards andpintai 1s migrate down f 1 tght corridorsfrom Canada to the Uni ted States east ofthe Rocky Mountains (Bell rose 1968). Thelargest portion, about 12,275r000~ enterthe geographical conflnes of theMisslssfppf Flyway from the northern GreatPlajns. About 20% of these bi rds continueacross the Mfssissippl Flyway and movedown the Atlantic Flyway. In addition,another 650.000 b1 ack ducks move southfrom Ontario and Quebec.Several corridors carrying dabblingducks cross the Great takes regfon (Figure67 1. An estimated 65,000 ma1 1 ards, 35,000wlgeons, and 25,000 p intaf 1 s move eastwardalong the Chesapeake Bay Corrfdor,startfng in the upper Mississippi Riverval 'ley and progressing through W I scons i n ,Michigan, and Ohlo, It encompasses themarshes of Lake Erie from MonroerMichigan* to Sandusk~r Ohio. From thesemarshes 5% Is a 645-km, nonstop f7 lght toChesapeake Bay, where most of these duckswinter. The Black Duck Corridor extendssouthwestward from eastern Ontario* acrossthe west end of Lake Erfe t o theconfluence of the Wabash and Oh10 rivers,and on south to Arkansas. Approximately35.000 black ducks use this path.Qfvina ducks, As the name suggests*these ducks normally dive below the waterfor food. About 4,200,000 diving ducksannually migrate south into the UnitedStates east of the Rockies (Be11 rose1968). $1 ightly over 60% of these arescaup, mostly lesser scaups. Redheads aresecond in abundance at 20%, whilecanvasbacks and ring-necked ducks eachform about 7% of the population. As withthe dabbling ducks, numerous diving duckmigration corridors cross the Great Lakesregion (Figure 68).The Southern Michigan Corridor takesthe main flow of diving duck passage fromeastern Wisconsin, across southern Michiganto Saglnaw Bay and the Lake St.Clair-Detroit River-Lake Erie wetlandsareas. Diving ducks congregate on SaginawBay to the extent that peak numbersInclude 22,000 lesser scaups, 22,000redheads, and 7,000 canvasbacks. App roximately160 km t o the south, peakpopulations of 380,000 1 esser scaups,260r000 canvasbacks, and 42,000 redheadshave been observed from Lake St. Cl ai r towestern Lake Erle. Although as many as15,000 dlving ducks may winter on theDetroit River, at least 700,000 fly onfrom Lake Erie to wintering grounds in theAtlantic Flyway. This route is known asthe Chesapeake Bay Corridor and is astmilar route to the one taken by mallardsand pintails. The Central Ohio Corrido-ris a flight path that extends southwardfrom Lake Erfe to Florida. Radarobservations of diving ducks movdng southpast Columbus, Ohlo, and band recoveriesfrom lesser scaups and redheads f ndicate apassage of over 100,000 divers along thiscorridor.GeeseA More than any other speciesof waterfowl, Canada geese have radicallyaltered their mlgratfon routes In the pastfew decades. Bell rose (1968) attributesthis great change fn their migrationhabfts to their rapid adoption of newly