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13.2.15. Hum anDisturbances of

Wate rfow l: Cau se s,

Effe cts, and

Management

Carl E. KorschgenU.S. Fish and Wildlife S ervice

Northern Prairie Wildlife Research Center

La Crosse Field S tation

P.O. Box 2226

La Crosse, WI 54602

and

Robert B. Dahlgren

U.S. Fish and Wildlife S erviceOffice of Refuge B iology

P.O. Box 2484

La Crosse, WI 54602

Hum an disturba nces of waterfowl can beintent ional or un intent ional. They may resu lt fromovert or directed a ctivities or ma y be an cillary toactivities not init ially thought to be of concern tobirds. Some of these distu rbances ar e man ifestedby alert ness , fright (obvious or ina ppa ren t), flight,swimming, disablement, or deat h. Ther efore,

persons r esponsible for water fowl ma nagementar eas should be aware of the pr oblems from h uma ndisturbance and should design m ana gement andfacilities that increase public appreciation of waterfowl.

In th e last 20 year s, the intensity of water -based recreation increased dr ast ically,especially on inla nd wa ter s. Wat erfowl ar e war y,seekin g refu ge from a ll forms of distu rba nce,part icularly th ose associat ed with loud noise an d

ra pid movement . Occasionally, the problem of hum an distur bance of water fowl resulted in forma llitigation. In Nevada , for examp le, th e RefugeRecreat ion Act of 1962 was affirm ed to per mitrecreational use only when it did n ot interfere withthe pr imar y purpose for which t he Ruby LakeNa tional Wildlife Refu ge was es ta blished.Compat ibility of an activity is bas ed on site-specificeffects on th e ma jor pu rp oses for which a r efugewas esta blished. In a r ecent su rvey of har mful andincompa tible us es on na tional wildlife refuges, 42

use categories were deter mined t hat could bepotential disturbances of waterfowl.

Activities That Cause

Disturbances

Given t he frequency of huma n distu rbance of water fowl, informat ion from research about thisissue is scant . A review of several t housan d jour nalar ticles and books revealed that most distu rbances

ar e crea ted by wat er us ers (chiefly boat ers,anglers, hunt ers) and aircraft (Table). Humanactivities cause different degrees of disturbance towater fowl an d ma y be grouped into four ma incategories. Listed in order of decreas ingdistur bance these categories are

1. rapid overwater movement and loud noise(power-boat ing, water s kiing, aircra ft);

2. overwater movement with little noise (sailing,wind s ur fing, rowing, canoeing);

W A T E R F O W L M A N A G E M E N T H A N D B O O K

Fish an d Wild life Leaflet 13.2.15. •• 1992 1

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3. litt le overwater m ovement or noise (wading,swimming); and

4. activities along shorelines (fishing,bird-wat chin g, hiking, and t ra ffic).

Distu rba nces displaced wat erfowl from feeding

grounds, increased energetic costs associated withflight, an d ma y have lowered pr oductivity of nestin g or brooding water fowl. Many au thorseither directly or indirectly implicated themselvesas a cause of distu rban ce during th eir studies of waterfowl.

Effects on Breed ing Waterfowl

Ann ual increases in wat erfowl numbers ar edetermined by several components of reproduction,including th e nu mber of breeding pairs, hat ching

success, and sur vival of the young. Huma ndistur bance can reduce several of thesecomponents, a nd, in t ime, result in a decliningwaterfowl population.

Declining Numbers of Breeding Pairs

Distu rban ces dur ing critical times of thenest ing cycle eventu ally cau se ducks to nestelsewhere or not to nest at all. In Maine, Americanblack ducks and ring-necked du cks did n ot n estun der conditions of excessive h uma n disturba nce.Mallards a t the Seney Na tional Wildlife Refuge in

Michigan failed to nest in a rea s open t o fishing .Some Wisconsin lak es bordered by homes were s oheavily used for recreation tha t br eeding ducks didnot use otherwise suitable habita t. In Germa ny, an85% decrea se of th e breeding s tock of ducks at twosma ll ponds p resum ably was caused solely bydistur bance from an increasing nu mber of anglersdur ing the wa terfowl breeding season. Num bers of ma llards, green-winged teals, norther n sh ovelers,pocha rds, an d tu fted ducks decreased from 26 pa irsto 4 pairs dur ing an 8-year p eriod. Huma n a ctivityon islands can a ltogether discourage nest ing inwaterfowl.

Increased Desertion of Nests

Stu dies of severa l species of wat erfowlidentified huma n distur bances as the cause of desertions or aba ndonment s of nest s, especiallydur ing early incubation. Distur bance fromobservers caused a 10% nest a bandonmen t ra te byma llards using ar tificial nest bask ets in a n Iowastu dy. Frequ ent visits t o goose nest s by biologists

Table. Hum an d isturban ces of wat erfowl by source of distu rban ce, effect, and n um ber of citations in 211

journal articles on the subject.

Subject Numberof cita tions

Sources of Disturbance ( in alphabetic order)

AircraftAirplanes 15Helicopters 10Genera l 22

Anglers (see fishing)Baiting/art ificial feeding 7Barges/shipping 9Boating (boats, canoes, rowing, airboats,

sa iling) 66Cats 2Development (indust rial, p ollution,

urban, const ruct ion) 24

Dogs 6Farming 19Fishing

Commercia l 5Spor t (angling) 50

Hazing (scaring) 12Human act ivity/distu rbance, genera l 58Hunting

Spor t 71Subsistence 2

Milita ry 5Noise 22Recreation

Genera l 18

Aquatic 27Research/investigator 55Roads

Genera l 10Traffic 11

Trains 1Trapping

Furbearer 1Water fowl 5

Effects ( in alphabetical order)

Breeding chronology in terrupted 2Brood breakup 14Brood rearing disrupted 7Energetic cost (flight) increased 23Family breakup 6Feeding in ter rupted or decreased 52Molting birds harrassed 9Nest/nesting

nest disturbed by r esearchers 55nest disturbed by others 27nest ing success reduced 14

Pr edation on clutches a nd chicksincreased because of research 31

Warin ess (alertn ess, tolerance distan ce) increased 43

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caused nest desertion rat es as high as 40%.Cana da geese nesting in south east ern Missouriwere very sens itive to pers ons fishin g in theirnestin g areas. Est ablishing area s closed to fishingdur ing the nest ing period decrea sed nestdesertions.

Reduced Hatching S uccess

Hum an disturba nce has th ree basic effects onnestin g success, that is:

1. exposure of eggs to heat or cold by flushing of hens m ay kill the embr yos;

2. predation of eggs may increase when hens areflushed from n ests; and

3. predation of eggs and hens may increase at nestswhen hum ans create trails or leave markers by

which predators find nests .When nests of cackling Canada geese were

checked several tim es before hat ch, twice th enu mber of eggs were lost t o predat ors. Wherehu ma n activities disturbed Can ada geese orcomm on eiders th at were nest ing amongblack-backed gulls, herring gulls, or parasitic

jaegers on islands or tun dra colonies, the gulls a nd jaeger s often quickly locat ed an d cons um ed eggs inwater fowl nest s u noccupied because of hum andisturbance.

Decreased Duckling Survival

Distu rban ce by hu ma ns dur ing the broodrear ing season can break u p an d scat ter broods orfrighten pa rent s into running ahea d of th eirducklings or goslings. Young waterfowl brieflyseparated from t heir mother are vulnerable topreda tors and s usceptible to death from severeweat her or lack of experience in obta ining food.Disturbances drastically increase kills by gulls of common eider ducklings. For example, the numberof eider du cklings killed by gulls in Sweden was200−300 times greater wh en broods were disturbed

by boat s. In n ort hern Maine, American black duckan d ring-necked duck broods avera ged two fewerducklings because of mortality from distur bance bymotorboat s. Hu ma n disturba nce caused a higherthan normal mortality rat e of trum peter swancygnets in a study ar ea in Alaska. Hum andistur bance can be quite brut al and direct; waterskiers an d power boaters h ave run overwhite-winged scoter hens and broods, and someboaters h ave used paddles t o kill ducklings.

Effects o n Non breeding

Waterfowl

Migrat ory and wintering water fowl generallyat temp t to minimize time spent in flight an d

ma ximize time for feeding. Flight requ iresconsiderably more ener gy tha n a ny other activity,except egg laying. Hum an disturba nce compelswat erfowl to change food ha bits, feed only at night ,lose weight, or deser t t he feeding ar ea. Wat erfowlrespond both to loud n oises an d ra pid movement s,such as boats powered by outboard m otors, an d tovisible featu res, such a s sa iling boat s. Large flocksof water fowl ar e m ore susceptible to distu rban cestha n s ma ll flocks.

Not all wat erfowl species ar e equa lly sens itiveto distu rban ce, and some ma y habitua te to certa indistur bances. Pink-footed geese were distur bed at a

distance of 500 m when m ore than 20 cars p er dayused a r oad in th e fall. Tra ffic of as few as 1 0 carsper day a lso had a depressing effect on ha bitat useby geese. Thus, the su rround ing buffer ar ea mu stexceed 500 m to ren der h abit at acceptable to flocksof pink-footed geese. Some waterfowl, especiallydiving ducks (notably canvasbacks a nd lesserscaups) and geese (notably brant s a nd sn ow geese)ar e especially vulnera ble to disturba nce. Densityand patt ern of distur bance ma y influence divingducks more than d abbling ducks in most areas .Repeated distu rba nces also can deny birds accessto preferred feeding ha bitats . Use by diving du cksof severa l good feeding ar eas a long the Upp erMississippi River h as been limited prima rily byboat ing disturban ces tha t cause 90 percent of th ewater fowl to concentr at e on 28 per cent of the stu dyarea during daytime.

Increased En ergy Expendi ture and

Depleted Fat Reserves

In t he absence of disturba nce, brant s in GreatBritain spent an average of 1.1% of their time inflight , but distur bance on weekends caused t he

time spent in flight to increase a s mu ch assevenfold a nd prevented br an ts from feeding for upto 11.7% of th e tim e. Detailed st udies a re few, butobservations su ggest tha t the effects of intensiverecreation during t he fall and winter could bedeleterious to m igrat ing an d winter ing waterfowl.

Researchers who at tempt ed to qua ntify th ehar m from distur bances on migrating andwintering waterfowl indicated that frequency of distur bance, num ber of affected birds, a nd cha nges


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in behavior ar e greater t ha n most su spected. Forexam ple, each du ck and Amer ican coot onHoughton Lake, Michigan, was distu rbed on th eaverage of 1.5 times per weekday and more th an 2times during weekend days. On Navigation Pool 7of th e Uppe r Mississippi River, an a verage of

17.2 boats passed thr ough th e study area ea ch dayand r esulted in 5.2 distur bances per day and aminim um of over 4 min of ad ditional flight t ime perdistu rba nce of wat erfowl. Birds m ay ha ve flown u pto an a dditiona l hour each day becaus e of humandistur bances. Over 2500 tu ndra swans left th eirmost importan t feeding area on the UpperMississippi River in res ponse to two sma ll boats.

Chan ged Migration Patterns

Prolonged and extensive distu rban ces ma ycause lar ge num bers of wat erfowl to leavedistur bed wetlands a nd migrate elsewhere. Thesemovement s can be local in a rea s of plent ifulhabitat or more distant and perman ent in areas of spar se ha bitat, causing shifts in flyway migrat ionpat tern s. Extensive distu rban ces on migrat ion an dwintering area s ma y limit the use by wat erfowlbelow th e car rying capa city of wetlan ds. Dailydistur bance by boat ers ma y have been r esponsiblefor eliminating th e bran t population tha t oncespent November and December on Hum boldt Ba y,California.

Managem ent Considerat ions

Fort un at ely, num bers of breeding wa ter fowlusu ally increas e in r esponse to reduction oreliminat ion of huma n dist urba nces. For t he benefitof water fowl, th e har m from h uma n distu rban cesmus t be minimized or eliminated. Mana gementalternat ives tha t r educe hum an disturba nces of wat erfowl include:

1. increa sing the qua ntity, quality, and distribut ionof foods to compensate for energetic costs from

disturbances;2. establishing screened buffer zones ar oundimportan t wat erfowl roosting and feeding ar eas;

3. reducing the number of roads and a ccess pointsto limit accessibility to habitats;

4. creating inviolate sanctuar ies; and5. reducing th e sour ces of loud noises and rapid

movements of vehicles and machines.

Distur ban ces occu r chiefly during a ll crit icalpa rts of th e an nu al cycle of wat erfowl—nest ing,

brood rea ring, migra tion, and wintering. Each par tof th e cycle is cru cial to th e breeding a nd su rvivalof wat erfowl populat ions. Comm on to all par ts of th e cycle is distu rba nce while feeding, which ma yincrease flight time and decrease feeding time.Distu rban ces of nesting birds ma y caus e

aban donment of the nest, disruption of the pairbond, reduction in clutch size, increa sed eggmortality, abandonment of the nesting ar ea, andincreased predat ion of the n est. Disturba ncesduring brood-rear ing ma y caus e exhaust ion of youn g and a n increase in losses from preda tion.These distu rban ces can be lessened or th eir effectsmitigated on refuges or other a reas ma na ged forwater fowl. Because disturba nces are sometimescaused by pr ofessional wildlife ma na gers orresear chers and private citizens, creation of san ctua ries is often necessar y at critical times a nd

locations. Access to roads an d tr ails can be limit edfor professionals a nd for bird-wat cher s. Activitiesof other u sers of wildlife, such as tr apper s an dhu nter s, may have to be restricted in space andtim e; boatin g, an gling, campin g, an d picnickingma y be rest ricted similarly. Huma n distur ban ceoften is increa sed by viewing platforms a ndwat erfowl can be viewed at a closer dist an ce if th eplatform is screened with vegetation and ma demore like a blind. Proper screens an d appr opriat econt rol of noise let people r ea lly enjoy wildlife closeat hand.

Structures such as pum ping stations andma intena nce buildings on wildlife areas should bescreened and placed where necessary hu ma n visitscause th e least distur bance of water fowl.Distu rban ces, part icular ly at critical t imes of th eyear, can be red uced nota bly by rest ricting access of pedestrian s, aut os, and boats; by regulat ingactivities such a s farm ing, grazing, bait collecting,camping, hunt ing, fishing, and t ra pping; and byprohibiting the use of nets th at can ent ra p divingducks. Access by dogs an d other pet s should n ot bepermitt ed in critical area s during the nest ing andbrood-rear ing periods. Airboats , aircraft, and

all-terrain-vehicles are often useful to managers of water fowl and wetland, but t heir use mus t becarefully plan ned t o minimize harm from sight orsound. Constr uction of dikes, canals , wat er cont rolstructures, roads, and similar stru ctures a ndmilitary uses of wetlands or r efuge ar eas sh ould bescheduled for n on-critical times in th e ann ualact ivity cycle of wat er fowl.

Distu rba nce of feeding wat erfowl cansometimes be m itigat ed by acquiring feeding area s


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on privately owned land t o creat e a sa nctuar y or bypra cticing moist soil ma na gement and thu sincreasing the availability of highly nutritiousfoods in t he refuge or wetlan d ar eas. With car efulplannin g, deleterious effects of hu ma n disturba nceon waterfowl can be mitigated or eliminated by

creating sanctua ries in time and spa ce (Figs. 1and 2).

Mana gers mu st aggressively protect wat erfowlfrom a ny huma n disturbance that reducesproductivity and health of populations. Toaccomplish this goal, man agers m ust resolveconflicting int erest s between n eeds of th e publicand needs of wildlife and r esearchers m ust gathermore data to provide a greater r ange of management options.

Suggested ReadingÅhlun d, M., an d F. Götmar k. 1989. Gull preda tion on

eider ducklings S omateria m ollissima : effect s of hu man disturba nce. Biological Conservat ion48:115−127.

Bélanger, L., and J . Bédard. 1989. Responses of stagingsnow geese to hu man disturba nce. J ournal of Wildlife Management 53:713−719.

Bouffar d, S. H. 1982. Wildlife valu es versu s hu ma nrecreation: Ruby Lake National Wildlife Refuge.Tran sactions of the North American Wildlife a ndNat ura l Resources Conference 47:553−558.

Bra un , C. E., K. W. Ha rmon, J . A. Ja ckson, and C. D.Litt lefield. 1978. Man agem ent of Na tiona l Wildlife

Refuges in th e United Sta tes: its impacts on birds.Wilson Bu lletin 90:309−321.Bur ger, J . 1981. The effect of hu ma n activity on birds a t

a coast al bay. Biological Conser vation 21 :231−241.Dahlgren, R. B., and C. E. Korschgen. 1992. Huma n

distur ban ce t o waterfowl: an an notat ed bibliograp hy.U.S. Fish and Wildlife Service Resource Publication188. 62 pp.

Edin gton, J . M., and M. A. Edington. 1986. E cology,recreation, and tourism. Cambr idge UniversityPr ess, New York. 198 pp.

Korschgen , C. E., L. S. George, an d W. L. Green . 1985.Disturbance of diving ducks by boaters on amigrational staging area. Wildlife Society Bulletin

13:290−296.Liddle, M. J ., an d H. R. A. Scorgie. 1980. The effects of

recreation on freshwater plan ts and a nimals: areview. Biological Conservation 17:183−206.

Pomera nt z, G. A., D. J . Decker, G. R. Goff, an d K. G.Pu rdy. 1988. Assess ing impa ct of recrea tion onwildlife: a classification scheme. Wildlife SocietyBulletin 16:58−62.


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Spring and Su mmer

Ducks nest along dikes an d in the uplan ds, and geesenest in tu bs on end of lake. Fewer pa irs are n esting eachyear, and m an y nests are a bandoned or destroyed.Pr edation rat es are high, especially in disturbedar eas. Disturba nce factors seem to be aut omobiles on tourroutes, an glers on shores an d in boats on the lake, hikerson tra ils, and u sers of the observation t ower.

Females h at ch la rge clut ches, but survival of young islower th an expected.

Fall and w inter

The lake is an importa nt st aging area for severalspecies of diving ducks; large nu mber s of ducks a nd geesefeed in th e upland s on an d around the r efuge. Wat erfowlnu mbers ar e decreasing despite favorable habita t. Thefrequency of human distur bance seems to have increased,especially from hun ters, late sea son anglers and boater s,th e aut o tour, hikers, and wildlife watchers. It is alsoappa rent tha t refuge staff are spending a lot of timeworking on minor projects.

Fig . 1. Exa mple of wate rfowl refuge with excessive level of hu ma n dist ur ban ce of wat erfowl.


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Spring and summe r

• Provide educational informa tion so that the pu blicknows the effects of distur bances on th e predominantspecies.

• Seas onally close or rest rict use of au to tour. User s of au to tour must sta y in vehicles and stop in onlydesignated parking ar eas.

• Seasonally close or rest rict use of hiking an d canoe

trails.• Close or restrict th e fishing season during peak n esting

period.• Permit camping in only designated a reas.• Delay hay cut ting unt il most clutches have ha tched.• Prioritize and limit special use per mits.• Limit access un til most young wat erfowl are th ree

weeks old.

Fall and w inter

• Provide educational informa tion so that the pu blicknows the migration and wintering requirement s of th e predominant species.

• Reroute au to tour to areas of secondar y importa nce towaterfowl.

• Move or screen observation towers.• Close selected a rea s of th e refuge to public access.• Create volunt ary avoidance area s on federal an d stat e

waterways.• Modify regulations to restr ict distu rban ces from hu nting

and tra pping.• Move water pu mping sta tions away from bird

concentration areas.• Raise h igh qua lity waterfowl foods on refuge land .• Limit size and h orsepower of boats on th e lake.• Disallow use of air boats.• Obtain short term leases and prevent tr espass on

private lands that contain wast e grain.• Limit the t ime tha t refuge staff spend in h igh waterfowl

use areas.• Delay const ruction unt il non peak seasons.

Fig. 2. Examples of man agement pra ctices that ha ve reduced th e level of human distur bance of water fowl at a refuge.


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Appendix. Comm on a nd Scient ific Na mes of Birds Named in Text.Ducks

Nor the rn sh oveler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anas clypeata

Green-winged teal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ana s crecca

Malla rd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anas platyrhynchos

Amer ican black duck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anas rubripesLesser sca up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aythya affinis

Ring-necked du ck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aythya collaris

Comm on pochard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aythya ferina

Tuft ed du ck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aythya fuligula

Can vas back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aythya valisineria

Whit e-winged scoter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Melanitta fu sca

Comm on eider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S omateria m ollissim a

Geese

Pink -footed goose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anser brachyrhynchus

Sn ow goose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anser caerulescens

Bra nt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Branta bernicla

Cana da goose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Branta canadensisCackling Cana da goose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Branta canad ensis minim a

S w a n s

Tru mpet er swan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cygnu s buccinator

Tun dr a swa n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cygnu s columbianu s

OtherAmer ican coot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fulica americana

Her rin g gull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Larus argentatus

Grea t black-backed gull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Larus m arinus

Para sit ic jaeger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S tercorarius parasiticus

UNITED STATES DEPARTMENT OF THE INTERIORFISH AND WILDLIFE SERVICE

Fish and Wildlife Leaflet 13Washington, D.C. •• 1992

8

Note: Use of trade na mes doe s not imply U.S. Governm ent endo rsemen t of comm ercial products .

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