Although scaup have always occurred in reasonable numbers in our state, they did not appear to be the explicit target of the diver hunter in years gone by. This is supported in part by the fact that scaup (also known locally as bluebills or blackheads) were never well represented in the North Carolina decoy culture of the early 20th century. However, as many hunters will attest and as waterfowl sur- vey data support, scaup numbers and hunting success in North Carolina can be outstanding most years. Over the last two decades, surveys in our state have documented that numbers of wintering scaup have trended upward, with numbers above their long-term average in most years. Couple this with the fact that the proportion of the total state duck harvest comprised of scaup has increased dramatically over the last 10 years, from around 5 percent to 12 to 15 percent, and it is evident that scaup numbers—or at least the pursuit of scaup — has increased tremendously. The irony of our success and the documented increase in our numbers of wintering scaup is that the overall continental popula- tion is declining dramatically. Those hunters who actively pursue scaup are well aware of this because, in response to the decline, scaup hunting regulations have become increasingly conservative. Just 10 years ago the daily bag limit for scaup was five. This year the allowable bag limit is only one per day for that portion of the season prior to Jan. 2, and two birds per day for the remainder. The continental population of scaup (both greater and lesser scaup combined), as measured by the comprehensive spring breeding population survey, has declined from highs of 7 million birds as recently as the mid-1980s to just around 3.5 million birds today. This quick, dramatic decline has left researchers and managers scratching their heads as to the cause and what, if anything, can be done to reverse this trend. There are several plausible theories; but first, more background. december 2008 winc 15 despite an upward trend in North Carolina, the continental population of scaup is declining dramatically, and a definitive cause has yet to be uncovered. BLUEBILLS bad days for Written by Joe Fuller Photographed by F. Eugene Hester d iver hunting is a time-honored tradition in North Carolina. From the famed canvasback hunting on Currituck Sound in the early part of the last century, and on the Pamlico Sound through the 1970s, to the traditional redhead hunting along the southern Outer Banks and Core Sound, hunting for diving ducks in North Carolina has a rich history and a dedicated following.
Transcript
Although scaup have always occurred in reasonable numbersin our state, they did not appear to be the explicit target of thediver hunter in years gone by. This is supported in part by the factthat scaup (also known locally as bluebills or blackheads) werenever well repre sented in the North Carolina decoy culture of theearly 20th century.
However, as many hunters will attest and as waterfowl sur -vey data support, scaup numbers and hunting success in NorthCarolina can be outstanding most years. Over the last two decades,surveys in our state have documented that num bers of winteringscaup have trended upward, with numbers above their long-termaverage in most years. Couple this with the fact that the proportionof the total state duck harvest com prised of scaup has increaseddramatically over the last 10 years, from around 5 percent to 12to 15 percent, and it is evident that scaup numbers — or at leastthe pursuit of scaup — has increased tremendously.
The irony of our success and the documented increase in ournumbers of wintering scaup is that the overall continen tal popula -tion is declining dramatically. Those hunters who actively pursuescaup are well aware of this because, in response to the decline,scaup hunting regulations have become increasingly conservative.
Just 10 years ago the daily bag limit for scaup was five. This yearthe allowable bag limit is only one per day for that portion of theseason prior to Jan. 2, and two birds per day for the remainder. Thecontinental population of scaup (both greater and lesser scaupcombined), as measured by the comprehensive spring breedingpopulation survey, has declined from highs of 7 million birds asrecently as the mid-1980s to just around 3.5 million birds today.This quick, dramatic decline has left researchers and managersscratching their heads as to the cause and what, if anything, canbe done to reverse this trend. There are several plausible theories;but first, more background.
december 2008 winc 15
despite an upward trend in North Carolina,
the continental population of scaup
is declining dramatically, and a
definitive cause has yet to be uncovered.
BLUEBILLSbad days
for
Written by Joe FullerPhotographed by F. Eugene Hester
diver hunting is a time-honored tradition in North
Carolina. From the famed canvasback hunting on
Currituck Sound in the early part of the last century, and on
the Pamlico Sound through the 1970s, to the traditional
redhead hunting along the southern Outer Banks and Core
Sound, hunting for diving ducks in North Carolina has a rich
history and a dedicated following.
include minnows and game fish, and agri -cultural sedimentation into natural wetlands.
Although there have been obvious declinesin body condition of scaup migrating throughthis area, and also forage declines as well,researchers do not know whether these con -ditions are experienced by enough scaup to cause impacts to the continental popula -tion. Several questions remain unanswered.Have birds simply shifted their migration pat-terns to avoid these areas with poorer foodresources, and /or can scaup compensate byacquiring sufficient nutrients farther north?Limited studies farther north in the borealforest suggest that birds arriving in such loca-tions have similar body mass, nest initiationdates and clutch size when compared to somehistorical estimates— a note of contradictionto the spring condition hypothesis. A remain-ing question, critical to this theory, is theinfluence of reduced body condition on afemale scaup’s ability to breed or even migrateto northern locations.
Contaminants. In association with bothdecreased forage quality and quantity, addi -tional research has focused on the idea thatenvironmental contaminants may be affect -ing scaup reproduction in some fashion.
Reproduc tion can be influenced in one ofseveral ways, including decreased propen -sity to nest, lower clutch size and reducedhealth of developing ducklings.
After ruling out a host of possible con -taminants, research has focused on the pos -sibility of reproductive impairment due tohigh concentrations of selenium and /or cad -mium in the environment. Selenium andcadmium are essential trace elements butcan impair health and reproduction whenacquired in high concentrations. Researchconducted on the industrialized portions ofthe Great Lakes has confirmed that scaupacquire large amounts of selenium throughtheir foraging on zebra mussels. This non-native and highly invasive species is a rela -tively new food item in the Great Lakes regionand appears to be a preferred food for scaup,yet these mussels are very efficient accumu -lators of contaminants and are responsiblefor the decline in native mussels.
However, additional research has shownthat selenium levels from scaup eggs collectedon their breeding grounds are below criticallevels, and selenium levels in nesting femalescollected on the breeding grounds had muchlower concentrations than females collected
on wintering and staging areas. So it appearsthat if scaup are acquiring high levels of sele-nium in the Great Lakes or other locations,they are able to eliminate much of it by thetime they reach their breeding locations.
Though this might suggest that seleniumis unlikely to cause problems for breedingscaup, questions remain as to whether high concen -trations of selenium arecausing females neverto reach their far northbreed ing grounds, or if the birds do arrive,whether they simply failto breed there. In contrast toresearch results from industrial portions of the Great Lakes, selenium levels in scaupcol lected in other areas, including moreremote areas of the Great Lakes and various
Source: Mid-Winter Waterfowl Survey
Scaup may be acquiring excessive amountsof selenium by feeding on zebra mussels(above), an exotic species found in theGreat Lakes. The mussels accumulate avariety of contaminants and appear tobe a preferred food for scaup.
U.S. GEOLOGICAL SURVEY, BUGWOOD.CO
M
Wintering Numbers of Scaup in North Carolina1961– 2008
Although North Carolina hunters haveseen increasing numbers of winteringscaup, the continental population hasfallen by about half since the mid-1980s.
consists of invertebrate amphipods, alsoknown as freshwater shrimp or scuds. Sev -eral researchers have noted that amphipoddensities in these wetlands are much lowerthan historical levels, and concomitantlythat scaup are acquiring fewer amphipodsthan they did earlier. There are a host of rea sons to explain the documented declineof amphipod densities in this region. Theseinclude natural invasion and purposefulstocking of amphipod predators, which
Because plumage of greater and lesserscaup is nearly identical and thus cannot bedifferentiated in aerial surveys, breeding pop-ulation estimates incorporate both species.However, the total estimate is likely comprisedof about 89 percent lesser scaup. Althoughscaup have certainly declined over time, thisdecline has not been consistent over theirgeographic range. In fact, scaup numbershave remained relatively stable in the prairiepothole region of the United States and theAlaskan tundra, the latter being the strong -hold of greater scaup.
However, scaup populations have declinedby 50 percent in the boreal forests of Canada’sNorthwest Territories and Alaska, a vast areathat accounts for nearly 50 percent of thetotal scaup population. Most scaup breed ingin this area are lesser scaup. Therefore mostauthorities concur that the decline in scaupshould be attributed to lesser scaup.
Waterfowl population dynamics are drivenby two important factors: survival and repro-duction. Unraveling the reasons for the scaupdecline begins by taking a hard look at thesetwo factors. This is where the head-scratchingbegins. Large-scale annual survival rate esti -mates are generally derived from extensiveand expansive banding studies. Unfortunately,a consistent and large-scale banding effort forscaup over time is lacking. Available band ingdata suggest that adult survival rates haveremained relatively unchanged over the longterm. Although impacts to scaup survivalfrom hunting or some other cause such as
disease cannot be ruled out, many researchersare focusing their attention on the reproduc -tive side of the population equation.
Three TheoriesHabitat conditions on spring staging areas.A principal hypothesis focuses on the role ofspring migration habitats and related foodavailability and quality, and their resultinginfluence on reproduction. This has beendescribed as the spring condition hypothesis.This theory asserts that reproductive suc -cess has decreased because females are arriv-ing on the breeding grounds in poorer bodycondition than they did historically. To testthis theory, scaup have been collected at var-ious locations in the Mississippi Flyway inlate winter and spring to measure indices ofbody condition, including body mass andnutrient reserves (lipid, protein and mineral).
Collections from the 1980s provide a com -parison to these recent collections in theearly 2000s. In general, researchers havefound that the body condition of scaup wasactually higher in southern areas of the fly -way (Louisiana and Illinois) than recordedin the 1980s. But the condition after the birdsleft key staging areas in Illinois was signifi -cantly lower when compared to the 1980s. Insummary, body condition of scaup on springmigration is fine in Illinois but becomes poorafter leaving this general area and headingfarther north. The poorer body conditionobserved likely affects breeding propensity,i.e., the likelihood for females to nest, andoverall reproductive success.
To investigate what factors might be affect-ing scaup body conditions, a review anddetailed look at scaup food habitats wereundertaken. The prime spring forage itemfor scaup, especially in the upper Midwest,
16 december 2008 winc
is exacerbating the decline is debatable.Exten sive data with which to quantify therelationship of harvest and population dyna-mics is for the most part lacking. The avail -able data include the annual breeding popu -lation survey, harvest estimates and limitedbanding data, where survival and harvestrates are inferred.
Using this information, the U.S. Fish andWildlife Service, with input from partners,has developed a model that looks at therelationship of the scaup population and har-vest. This model suggests that current levelsof harvest are approaching or exceeding theharvest potential of the population. Statedsimply, harvest may be exceeding the abilityof the population to sustain itself throughcurrent levels of survival and reproduction.However, this model is not without its detrac-tors, who believe that harvest is playing norole at all in the population decline. Becauseharvest is really the only thing that can becontrolled by waterfowl managers, and giventhe possibility that harvest may be playingsome role, further harvest restrictions wereenacted this year and likely will remain inplace for at least several years.
The process by which a harvest reductionshould occur through adjustments of seasonlength and bag limits presents a dilemma forstate wildlife agencies. Most managers agreethat a reduction in the daily bag limit from twoto one will almost certainly impact hun terparticipation. Many big-water diver hunters
simply will not gear up for scaup, and thiswill impact both short- and long-term trendsin duck hunting participation. Conversely,allowing a higher bag limit of two or threescaup for a limited number of days and noscaup for the remainder of the 60-day duckseason is unsatisfactory to managers whodesire the least-complicated regulations pos-sible, and also because of concerns aboutduck misidentification.
A short scaup season within the generalduck season is a real concern for states thatwinter large numbers of ring-necked ducksand is problematic for hunters where ring -necks and scaup comingle. The uninten tionalhar vest of a scaup during hunting for ring -necks and other species is a valid concern tostate managers and law enforcement. For the2008–2009 duck season, the Atlantic Fly -way successfully lobbied for a “hybrid” sea -son that allows for 20 days with a daily bag oftwo scaup; the remaining 40 days permit onescaup per day. This should allow some timefor traditional diver hunters to make it worth -while to pursue scaup. In addition, allowingat least one scaup per day for the entire seasonwill ease the misidentification issue.
Next StepsAt more than 3 million birds, scaup are obvi -ously still quite numerous; however, theirunabated decline is of great concern. Thoughprogress is being made to under stand the fac-tors behind this decline, strate gies necessary
to stop or reverse the trend really do not exist.In contrast to the situation with many prairie-nesting ducks, a good nesting cover programlike the Conservation Reserve Program andabundant rainfall are not the key elementsin turning the tide for scaup.
Of the three leading hypotheses, allinvolve some aspect of long-term environ -mental change, and none offer a quick remedy.A Scaup Action Team working under thebroad auspices of the North American Water-fowl Management Plan is a newly formedgroup of scientists and resource managerswho hope to focus attention on the plight ofscaup and to help guide scaup research appro-priately. There is the distinct possibility thatall three theories may be acting in concertand playing a role in the decline. Manyexperts believe that if scaup are respondingto long-term environmental changes, the pop-ulation will equilibrate at a point that can besupported by habitat and environmental con-ditions. But at this point it’s anyone’s guess atwhat level the population will stabilize. Let’shope this occurs sooner rather than later.
Joe Fuller is the migratory game bird coordi na-tor for the N.C. Wildlife Resources Commission.
Climate change might be playing a role inthe substantial reduction of scaup breed-ing populations in the boreal forests ofAlaska and western Canada.
december 2008 winc 19
DUCKS UNLIMITED CANADA
18 december 2008 winc
when scaup ingest the exotic faucet snail.The causative agents, however, are two para -sitic trematodes (flatworms) that use thefaucet snail as their host. Depending on thelevel of snail infection, a lethal dose can beacquired in less than 24 hours of feeding, anddeath occurs within three to eight days. Atthis time, the disease itself is not thought to be a significant contributor to the conti -nental decline of scaup. Nevertheless, thissituation warrants close monitoring and isanother example of the many environmentalchallenges facing scaup today.
The Role of HuntingThe role of hunting in the decline of scauphas been a controversial and, quite frankly,contentious issue among resource managers.Most biologists agree that hunting is not theroot cause of the scaup population decline.However, the extent to which current harvest
After exceeding management plan goalsin the 1970s and ’80s, scaup populationshave declined rapidly and now stand atabout 3.5 million birds.
communities, including a reduction in foodssuch as amphi pods that scaup hens andducklings prefer to eat.
Role of DiseasesOther factors could be playing a role in thedecline of scaup. The impact of disease mor -tality on waterfowl populations is often diffi -cult to quantify, and whether these factors candepress waterfowl populations over the longterm is largely unknown. There is growingevidence that numbers of waterfowl lost todisease have increased substantially inrecent decades. Scaup, like other waterfowl,are susceptible to a variety of diseases andlikely have coexisted with them for eons.However, since 2002 approximately 30,000waterbirds (primarily lesser scaup and coots)have died from a newly emerging diseasefound in upper portions of the MississippiRiver and Minnesota. The disease occurs
Breeding Population Estimates of Scaup 1955 – 2008
Source: Waterfowl Breeding Population and Habitat Survey
places throughout the Midwest, appearwithin nor mal background levels. However,research conducted in these areas suggeststhat con centrations of cadmium are at ele -vated levels and may play some role in affect-ing nutrient and lipid reserves.
Environmental changes on the breedinggrounds. The third principal hypothesisinvolves environmental changes to wetlandhabitats in the western boreal forests ofAlaska and Canada. Although densities ofbreeding waterfowl are relatively low through-out the boreal forest, the sheer vast ness ofthe area (1.8 million square miles) accountsfor up to 40 percent of the conti nental duckpopulation each year. Although the prairiepothole region is referred to as the “duckfactory,” the importance of the boreal forestis recognized by its own nickname as “theother duck factory.”
The western boreal forest is pristine innature, a seemingly unspoiled wildernessmiles from significant human habitat andinfluence, but changes are occurring there.Increasing oil and gas exploration and devel-opment, and industrial forest management,are viewed as threats to wetland habitats inthe area. In addition, climate change has beendocumented as causing profound changes towetlands. Currently, we know that the climateis warming at a faster rate in higher latitudes,including the boreal forest. In fact, this areahas warmed about 2 degrees Celsius (3.6degrees Fahrenheit) over the last 30 years.
Although warming trends generateincreased precipitation, higher evaporationrates due to warmer temperatures are caus ingwetlands, especially smaller wetlands favoredby scaup, to dry. Permafrost, which holdswater at the surface, is now starting to thaw,allowing water to be channeled out of wet -lands into adjacent surface waters or becomelost to groundwater systems. Melt ing of per -ma frost also increases the water-holdingcapacity of upland soils, which reduces run -off into adjacent wetlands. Researchers havedocumented a loss of nearly 25 percent ofsurface water on several important scaupbreeding areas in Alaska, mostly in the last20 years. In addition, research suggests thatchanges in water chem istry due to warmingconditions are causing shifts in invertebrate
