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561 SPATIOTEMPORAL HETEROGENEITY OF GREATER SNOW GOOSE HARVEST AND IMPLICATIONS FOR HUNTING REGULATIONS ANNA M. CALVERT, 1 Département de Biologie and Centre d’Études Nordiques, Université Laval, Sainte-Foy, PQ, G1K 7P4, Canada GILLES GAUTHIER, 2 Département de Biologie and Centre d’Études Nordiques, Université Laval, Sainte-Foy, PQ, G1K 7P4, Canada AUSTIN REED, Canadian Wildlife Service, 1141 Route de l’Église, Sainte-Foy, PQ, G1V 4H5, Canada Abstract: Changes in harvest rate over the past 3 decades have been shown to be closely related to population growth of greater snow geese (GSG; Chen caerulescens atlantica). We used band-recovery and harvest survey data from 1970 to 2001 to study temporal variations in geographic harvest distribution and composition of GSG in Québec, Canada and the Atlantic Flyway states (AF) in the United States. We sought to determine whether (1) geo- graphic variation in harvest was associated with temporal trends in total harvest rates observed during this period; (2) spatiotemporal distributions of harvest varied with age and sex; and (3) harvest distribution and composition differed between the spring conservation harvest initiated in 1999 and the regular fall hunt in Québec. We detect- ed over time a gradual spreading in the geographic distribution of the fall harvest from the upper St. Lawrence estuary toward southwestern Québec. During winter, a sudden northward shift in the distribution of the United States harvest in the mid-1980s was associated with a high concentration of geese in mid-Atlantic Flyway states (Maryland, Delaware, and New Jersey), possibly due to short-stopping during migration. We argue that this led to a reduction of hunting pressure on GSG and may have contributed to the sudden decline in harvest rate that occurred at that time and ultimately to the ensuing population increase. We observed a decreasing proportion of juveniles in the kill throughout the hunting season within fall staging grounds in Québec and between Québec and the United States. We also found a much higher proportion of adults in the spring harvest than in the fall that is consistent with the conservation goal of increasing the adult harvest. We recommend that management actions focus on increasing harvest in mid-Atlantic Flyway states if further control of population growth is desired. JOURNAL OF WILDLIFE MANAGEMENT 69(2):561–573; 2005 Key words: Atlantic Flyway, Chen caerulescens atlantica, conservation harvest, greater snow goose, harvest distribution, Québec, staging distribution, wintering distribution. Hunting mortality has been often implicated as a factor influencing waterfowl demography (Smith and Reynolds 1992, Francis et al. 1998), especially for long-lived species with low natural mortality rates, such as geese (Hestbeck 1994, Francis et al. 1992a, Gauthier et al. 2001). How- ever, hunting intensity may change over time and among regions, and harvest may not equally affect all groups within a targeted population; such variations require consideration in the development of management schemes. Many goose populations in the northern hemi- sphere have shown rapid growth in recent years, particularly in the 1980s and 1990s (Ankney 1996, Abraham and Jefferies 1997, Madsen et al. 1999). These increases have been attributed to the use of refuges that prohibit or limit hunting and to extra food available in agricultural fields (Krapu et al. 1995, Abraham and Jefferies 1997, Reed et al. 1998). Several breeding colonies of lesser snow geese (LSG; Chen c. caerulescens) have grown to levels where they have severely degraded sev- eral staging and breeding habitats (Abraham and Jefferies 1997). Similarly, the abundance of greater snow geese (GSG) has dramatically in- creased since 1965, although their impacts on habitats appear to be less severe (Giroux et al. 1998a, Reed et al. 1998). Due to the increase in abundance, hunting regu- lations for snow geese have been liberalized over the past 3 decades, and particularly since the mid- 1990s. For instance, daily bag limits for GSG during fall in southern Québec increased from 5 in the 1970s to 8 in the early 1990s and 20 in 1999, and during winter in the Atlantic Flyway (AF) states from 5 in the late 1970s to 15 in the late 1990s (Canadian Wildlife Service [CWS] annual migrato- ry birds hunting regulations summaries; J. Kelley, U.S. Fish and Wildlife Service [USFWS], personal communication). However, harvest rates of GSG dropped sharply in the mid-1980s and remained relatively low through the 1990s (Menu et al. 2002), and similar tendencies were observed for LSG har- vest rates (Francis et al. 1992a, Cooke et al. 2000). The period of snow goose population increases also was associated with a variety of changes in habi- tat use and migration timing and routes (Alisauskas 1998, Reed et al. 1998). In particular, fall staging 1 Current address: Biology Department, Dalhousie University, Halifax, NS, B3H 4J1, Canada. 2 E-mail: [email protected]

SPATIOTEMPORAL HETEROGENEITY OF GREATER SNOW GOOSE HARVEST AND IMPLICATIONS FOR HUNTING REGULATIONS

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SPATIOTEMPORAL HETEROGENEITY OF GREATER SNOW GOOSEHARVEST AND IMPLICATIONS FOR HUNTING REGULATIONS

ANNA M. CALVERT,1 Département de Biologie and Centre d’Études Nordiques, Université Laval, Sainte-Foy, PQ, G1K 7P4, CanadaGILLES GAUTHIER,2 Département de Biologie and Centre d’Études Nordiques, Université Laval, Sainte-Foy, PQ, G1K 7P4,

CanadaAUSTIN REED, Canadian Wildlife Service, 1141 Route de l’Église, Sainte-Foy, PQ, G1V 4H5, Canada

Abstract: Changes in harvest rate over the past 3 decades have been shown to be closely related to populationgrowth of greater snow geese (GSG; Chen caerulescens atlantica). We used band-recovery and harvest survey datafrom 1970 to 2001 to study temporal variations in geographic harvest distribution and composition of GSG inQuébec, Canada and the Atlantic Flyway states (AF) in the United States. We sought to determine whether (1) geo-graphic variation in harvest was associated with temporal trends in total harvest rates observed during this period;(2) spatiotemporal distributions of harvest varied with age and sex; and (3) harvest distribution and compositiondiffered between the spring conservation harvest initiated in 1999 and the regular fall hunt in Québec. We detect-ed over time a gradual spreading in the geographic distribution of the fall harvest from the upper St. Lawrenceestuary toward southwestern Québec. During winter, a sudden northward shift in the distribution of the UnitedStates harvest in the mid-1980s was associated with a high concentration of geese in mid-Atlantic Flyway states(Maryland, Delaware, and New Jersey), possibly due to short-stopping during migration. We argue that this led toa reduction of hunting pressure on GSG and may have contributed to the sudden decline in harvest rate thatoccurred at that time and ultimately to the ensuing population increase. We observed a decreasing proportion ofjuveniles in the kill throughout the hunting season within fall staging grounds in Québec and between Québec andthe United States. We also found a much higher proportion of adults in the spring harvest than in the fall that isconsistent with the conservation goal of increasing the adult harvest. We recommend that management actionsfocus on increasing harvest in mid-Atlantic Flyway states if further control of population growth is desired.

JOURNAL OF WILDLIFE MANAGEMENT 69(2):561–573; 2005

Key words: Atlantic Flyway, Chen caerulescens atlantica, conservation harvest, greater snow goose, harvest distribution,Québec, staging distribution, wintering distribution.

Hunting mortality has been often implicated asa factor influencing waterfowl demography(Smith and Reynolds 1992, Francis et al. 1998),especially for long-lived species with low naturalmortality rates, such as geese (Hestbeck 1994,Francis et al. 1992a, Gauthier et al. 2001). How-ever, hunting intensity may change over time andamong regions, and harvest may not equallyaffect all groups within a targeted population;such variations require consideration in thedevelopment of management schemes.

Many goose populations in the northern hemi-sphere have shown rapid growth in recent years,particularly in the 1980s and 1990s (Ankney 1996,Abraham and Jefferies 1997, Madsen et al. 1999).These increases have been attributed to the useof refuges that prohibit or limit hunting and toextra food available in agricultural fields (Krapuet al. 1995, Abraham and Jefferies 1997, Reed etal. 1998). Several breeding colonies of lessersnow geese (LSG; Chen c. caerulescens) have grownto levels where they have severely degraded sev-

eral staging and breeding habitats (Abraham andJefferies 1997). Similarly, the abundance ofgreater snow geese (GSG) has dramatically in-creased since 1965, although their impacts onhabitats appear to be less severe (Giroux et al.1998a, Reed et al. 1998).

Due to the increase in abundance, hunting regu-lations for snow geese have been liberalized overthe past 3 decades, and particularly since the mid-1990s. For instance, daily bag limits for GSG duringfall in southern Québec increased from 5 in the1970s to 8 in the early 1990s and 20 in 1999, andduring winter in the Atlantic Flyway (AF) statesfrom 5 in the late 1970s to 15 in the late 1990s(Canadian Wildlife Service [CWS] annual migrato-ry birds hunting regulations summaries; J. Kelley,U.S. Fish and Wildlife Service [USFWS], personalcommunication). However, harvest rates of GSGdropped sharply in the mid-1980s and remainedrelatively low through the 1990s (Menu et al. 2002),and similar tendencies were observed for LSG har-vest rates (Francis et al. 1992a, Cooke et al. 2000).

The period of snow goose population increasesalso was associated with a variety of changes in habi-tat use and migration timing and routes (Alisauskas1998, Reed et al. 1998). In particular, fall staging

1 Current address: Biology Department, DalhousieUniversity, Halifax, NS, B3H 4J1, Canada.

2 E-mail: [email protected]

J. Wildl. Manage. 69(2):2005562 HETEROGENEITY OF GREATER SNOW GOOSE HARVEST • Calvert et al.

GSG that were traditionally concentrated in marsh-es of the upper St. Lawrence estuary increasinglyused farmlands and considerably expanded theirrange into southwestern Québec, away from natur-al marshes (Olson 2001). A northerly shift in snowgoose wintering distribution was also noted in theAF states (Reed et al. 1998). These changes couldhave contributed to the decline in harvest rate ifgeese were less exposed to hunting in the newlyoccupied areas (Freemark and Cooch 1978).

In response to the perceived threat to naturalhabitats posed by the rapid population growth,the Arctic Goose Habitat Working Group of theArctic Goose Joint Venture, North AmericanWaterfowl Management Plan, recommended thataggressive conservation measures be implement-ed to stabilize the population size of GSG (Girouxet al. 1998b) and to reduce the abundance of LSG(Johnson 1997). These measures included theintroduction of a spring conservation harvest dur-ing April and May on agricultural staging groundsin Québec for GSG, and the relaxation of existingfall (Québec) and winter (AF) hunting regula-tions (i.e., higher bag- and possession-limits inboth seasons and the use of special hunting meth-ods in fall) for both subspecies, beginning in win-ter 1998–1999 (CWS Waterfowl Committee2001a,b). Based on evidence that harvest is closelylinked to survival in GSG (Gauthier et al. 2001,Menu et al. 2002, Calvert and Gauthier 2005), theincrease in harvest expected from these changeswas predicted to reduce adult survival and conse-quently to stop population growth.

We examined long-term variations in GSG har-vest using 2 sources of data: returns of metal leg-bands by sport hunters and national sport-harvestsurveys conducted by the CWS and USFWS.Specifically, our main objectives were to (1) deter-mine whether geographic variation in harvest inCanada and the United States over 32 years wasassociated with temporal trends in harvest ratesobserved during this period, (2) uncover any age-or sex-specific differences in temporal and geo-graphic distributions of harvest, and (3) establishwhether harvest distribution and compositiondiffered between the spring conservation harvestand the traditional fall harvest in Québec.

METHODS

DataGSG were leg-banded in several locations and at

varying intensities of banding effort from 1970 to2001 (n = 54,421). Most banding occurred from

1970 to 1974 (7,191 geese) and 1990–2001 (43,141);geese were banded primarily during the summer inNunavut (44,132), and most other bandingoccurred during staging in southern Québec(8,881) and winter in the AF (1,399). All birds weremarked with USFWS/U.S. Geological Survey(USGS) metal leg bands, and a subset (mainlyadult females; Menu et al. 2000) were fitted withplastic neck collars. We could not determinewhether birds marked with a collar had retained ituntil time of harvest, but collar loss is low in thispopulation (3–5%/yr; Gauthier et al. 2001, Reed2003). We obtained banding and recovery (n =6,571) records from the Bird Banding Laboratory(USGS). We used data on recoveries of all bandedindividuals killed and retrieved by hunters in aknown location; we did not use data from geesethat were radiomarked, reported by nonhunters,not shot, or not wild. Because GSG hunting seasonswere not offered in the AF until 1975, we only haddata since 1975 for the AF. Because individual hunt-ing seasons span 2 calendar years, hereafter wealways refer to a hunting season by the year it start-ed (e.g., the 1998 hunting season started in fall1998 and ended in spring 1999) in text and figures.

Our other source of data for Canada was theSpecies Composition Survey (SCS) database com-piled by CWS. Because the fall migration of GSGin Canada is largely limited to the province ofQuébec (Reed et al. 1998), we used SCS data forall snow geese harvested in Québec only (snowgeese reported from neighboring Atlanticprovinces and eastern Ontario represented only1.5% of the total reported for eastern Canada, n= 7,568 tails). The CWS distinguished GSG fromLSG in the harvest based on tail measurements;however, the annual proportion of LSG reportedin the Québec harvest based on this index (mean= 0.26, annual range 0.00–1.00) was unrealistical-ly high relative to the annual proportion of bluephase geese in the harvest (mean = 0.01, annualrange 0–0.06). Presence of blue geese was a use-ful marker to distinguish these 2 sub-speciesbecause blues were very rare in GSG (<1%, A.Reed, CWS and G. Gauthier, U. Laval, unpub-lished data), while eastern LSG breedingcolonies tend to include a very large proportionof blues (>70%, Cooke et al. 1995). We thus con-cluded that tail measurements were unreliable todistinguish the 2 sub-species. In the AF as well,proportion of blue geese in the harvest was mini-mal (mean = 0.02, annual range 0–0.04). Basedon these indices, we concluded that the true pro-portion of LSG in the reported harvest from

J. Wildl. Manage. 69(2):2005 563HETEROGENEITY OF GREATER SNOW GOOSE HARVEST • Calvert et al.

Québec and the AF was negligible, and like Reedet al. (1998) we pooled LSG and GSG.

Statistical Analyses In order to examine spatial and temporal varia-

tions in harvest distribution and composition andto determine how harvests from spring and fallseasons differed, we compared series of loglinearmodels using several different data sets based onband recoveries and tail returns (Table 1). Wesplit band recoveries between Canada and theUnited States to permit within-country regionalanalyses. We used total recoveries (all recoveriesof hunter-shot geese across all years) for analysesof temporal and geographic variations in harvestfrom 1970 to 2001. We used direct recoveries (i.e.,only those recovered within 1 calendar year ofbanding) to examine questions pertaining to agerepresentation in the harvest. We analyzed total-and direct-recovery data sets to determinewhether collars affected harvest distribution.Finally, we used a subset of the direct recoveriesto compare spring harvest and fall hunt inQuébec for 1998–2001, and we used a data setconsisting of the direct recoveries from bothcountries combined to look for large-scale differ-ences in the harvest between Canada and theUnited States. We used tail return data (availablefor Canada only) in temporal, geographic, andage-related analyses and for comparison withband recoveries, but, unlike band recoveries, tail

returns did not cover harvest from the springconservation harvest.

We conducted loglinear analyses for each dataset using PROC CATMOD in SAS (SAS Institute1999). Reported harvest was the dependent vari-able, with the number of harvested geese (tailreturns or band recoveries) partitioned accord-ing to the following independent variables: (1)region (for Québec, we defined 5 functional geo-graphic areas [Fig. 1], and for the AF, we com-bined pairs of adjacent states from north to south[Vermont and New York, Pennsylvania and NewJersey, Delaware and Maryland, and Virginia andNorth Carolina]), (2) age (juveniles [<1yr] vs.adults [≥1 yr]), (3) sex (band returns only), (4)season (spring and fall), (5) neck collar pres-ence, and (6) country. We further grouped datainto time blocks of 5 years starting in 1970, exceptfor 1995–1997 (3 years) and 1998–2001 (4 years),separated to distinguish pre- and during-springharvest years. Because of unequal interval length,we used the average annual number of harvestedgeese reported per time period as the dependentvariable instead of the total count. Two-way inter-actions among variables were often the statistic ofinterest for addressing our specific research ques-tions given that some variables were of little inter-est by themselves (e.g., variations in the numberof recoveries over time or region may simplyreflect variations in the number of birds bandedor in the size of regions, respectively).

Table 1. Important predictors of the distribution of greater snow goose harvest in eastern Canada and Atlantic Flyway (AF) states,USA, 1970–2001. For each data set, we show the combination of categorical variables and their interactions (*) that bestexplained variation in the number of geese harvested during regular-season sport-hunts in fall in Québec and in winter in AFstates, as well as during the special spring conservation harvest in Québec since 1999.

Data set a Best-fit models b ∆AICcc kd ωAICc

e

Canada total recoveries Region, age, time, collar, region*time, age*time, time*collar 0.00 64 0.758 U.S. total recoveries Region, sex, age, time, collar, region*time, age*time, time*collar 0.00 49 0.325

Region, sex, age, time, collar, region*time, time*collar 0.05 39 0.317Region, sex, age, time, collar, region*time, age*time, time*collar, age*sex 0.24 50 0.289

Canada/U.S. combined Country, sex, age, time, country*time, country*age, age*time, age*sex 0.00 21 0.449direct recoveries Country, sex, age, time, country*time, country*age, age*time 1.99 20 0.166

Canada direct recoveries Region, age, time, collar, region*age, time*collar 0.00 23 0.728 U.S. direct recoveries Region, age, time 0.00 11 0.330

Region, age, time, collar 1.76 12 0.137Region, age, time, region*time 1.82 15 0.133

Canada direct recoveries Region, age, season, age*season 0.00 8 0.625 (spring and fall 1999–2001)

Canada tail returns Region, age, time, region*time, age*time, region*age 0.00 46 0.996

a Data sets were made up of either total band-recoveries, direct (<1yr post-banding) band-recoveries, or tails returned as partof the National Harvest Survey.

b Variables retained in the most parsimonious model(s) among the candidates; we showed the best-fitting model for each dataset first, and we showed additional models if the best-fit model had ωAICc < 0.50.

c The difference between a model’s AICc value and the smallest value for that data set.d The number of model parameters.e The model’s AICc weight relative to all models in the data set (where all model weights sum to 1).

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We did not construct and compare all potentialmodels but only those that we considered biolog-ically appropriate following the principle of par-simony (Burnham and Anderson 1998). Thenumber of candidate models in each set rangedfrom 14 to 64 (mean 41), depending on the datatype and number of interactions considered. Themany factors and interactions considered result-ed in the selection of relatively complex models(i.e. with many parameters) from the candidateset because the large number of recoveries andtail returns provided us with datasets that couldsupport complex models with several effects. Foreach candidate model, we calculated the AkaikeInformation Criterion corrected for small samplesize (AICc), where the model with the smallestAICc value for that data set (or within <2 of themodel with the smallest AICc) and the largestAICc weight (ωAICc; the weight of evidence foreach model where the sum of all model weights =1) provided the most parsimonious fit to the data(Burnham and Anderson 1998). For the mostgeneral model of each data set, we also calculat-ed a measure of overdispersion (c ; Burnham and

Anderson 1998). Because in all cases c < 1, wemade no corrections for overdispersion.

Additional Harvest Calculations Harvest rates for 1975–1997 were recalculated fol-

lowing Menu et al. (2002). For the 1998–2001 sea-sons, we mimicked calculations of Menu et al.(2002) estimating harvest rate as the total annualharvest (Canada + United States) divided by fallpopulation size. We obtained harvest estimates forQuébec from the Canadian National Harvest Sur-vey (NHS) conducted by the CWS (P. Brousseau,CWS, unpublished data) and for the AF states fromthe United States federal survey (Martin andPadding 1999, 2000, 2001, 2002). We obtainedspring harvest data from a special harvest surveyconducted by the CWS that followed a rigoroussampling scheme similar to the NHS; informalage–ratio surveys were conducted by P. Brousseau(P. Brousseau, CWS, personal communication) inspring. We included the spring harvest with theprevious fall/winter harvest (e.g., the 2000 springharvest was added to that of the 1999 regular sea-sons as part of the 1999 hunting season).

Fig. 1. Limits of the geographic regions of southern Québec (stippled lines) used to group band recoveries and tail returns forgeographic comparisons of greater snow goose harvest distributions. Regional boundaries continue past the edge of theenlarged map to the political boundaries of the province of Québec. Grid lines show latitudes and longitudes.

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RESULTS

Collar EffectsOur analyses of band-recovery data (both total

and direct recoveries) showed no evidence of dif-ferential geographic harvest distribution betweenbirds with and without collars (the interactionregion*collar was never present in the preferredmodels; Table 1). The interaction time*collar wasretained but likely was spurious because collarswere rarely used before 1990. As a result, wepooled the 2 groups (collared and leg-banded-only) for other analyses that relied on subsets ofrecovery data.

Spatiotemporal Variation in HarvestThe region*time interaction was present in the

best models, suggesting that the geographic dis-tribution of harvest changed over time in Canadaand the United States (Table 1; the sum of AICc

weights [Σ ωAICc] of allmodels containing thiseffect was >0.999 forCanadian and UnitedStates total band recover-ies). The proportion ofCanadian band recover-ies coming from the St.Lawrence estuary de-clined gradually from96% in the early 1970s to52% in 1998–2001, withan increasing trend inall other regions, partic-ularly in the Lac-St-Pierre and border areas(Figs. 2A, 3). Canadiantail returns, which donot include spring har-vest data, showed similarspatiotemporal trends(i.e., the interactionregion*time was also pre-sent in the best model;Table 1; Σ ωAICc >0.999).The only differences werea lower contribution ofthe estuary to the totalharvest in 1998–2001(41%) compared to theband recoveries and aslightly higher contribu-tion of the Lac-St-Jeanarea (18%) during the

same period. In absolute terms, harvest increased inall parts of the province (Reed et al. 1998); however,while the mean annual number of bands recoveredin the estuary increased by a factor of 3 between the1970s and 1995–2001, it showed a 30-fold increasein the Lac St-Pierre and Border areas (Fig. 3).

In the AF states, winter band recoveries showeda marked and abrupt shift toward the north inthe mid-1980s (Fig. 2B). The proportion of bandscoming from Virginia and North Carolinadecreased from 62% in the late 1970s to less than9% in 1998–2001, and the proportions fromDelaware, Maryland, Pennsylvania, and New Jer-sey increased accordingly (Fig. 4). In absoluteterms, the mean annual number of bands recov-ered was reduced by more than half in Virginiaand North Carolina but increased by a factor of10 in Delaware and Maryland and by a factor of 4to 6 in more northern states between the late1970s and the late 1990s.

Fig. 2. Proportional distribution of total band recoveries of greater snow geese across Québecregions (A, n = 3,779) and Atlantic Flyway states (B, n = 2,542) within each time period,1970–2001. There was no hunting in the United States before 1975. The period 1998–2001included the spring harvest in Québec.

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The relative proportion of band recoveriesbetween the 2 countries also varied over time sincethe opening of the AF states’ GSG hunt in 1975(the country*time interaction was present in thebest model for the combined Canada/UnitedStates dataset; Table 1; Σ ωAICc = 0.875). Bandrecoveries were higher in the United States (63%)than Canada from 1975 to 1979 and also slightlyhigher in the UnitedStates during 1985–1989(51%), but most camefrom Canada in all otherperiods (56–77%).

Age and SexRepresentation in the Harvest

We found evidencethat age distribution ofthe harvest varied spa-tiotemporally. On alarge spatial scale, theproportion of juvenilesin the band recoverieswas much higher inCanada (69%) than inthe United States (44%;the country*age interac-tion was present in thebest model for the com-bined Canada/UnitedStates dataset; Table 1; ΣωAICc > 0.999). We alsofound spatial differ-ences in age distributionamong regions withinQuébec (the region*ageinteraction was presentin the best models forCanadian direct recover-ies and for tail returns;Table 1; Σ ωAICc = 0.810and > 0.999, respective-ly) but not among AFregions (the region*ageinteraction was not pre-sent for United Statesdirect recoveries; Table1; Σ ωAICc = 0.135). Thejuvenile proportion ofband recoveries de-creased from north tosouth in Québec, beinghighest (>70%) in the

estuary and Lac St-Jean areas and lowest (52%)along the Québec-United States border (Fig. 5);tail returns showed the same pattern. There wasalso evidence for temporal change in the age rep-resentation in the Québec fall harvest (age*timeinteraction present in the best model for tailreturns; Table 1; Σ ωAICc = 0.996), with adultsaccounting for a progressively larger share of the

Fig. 3. Distribution of greater snow goose band recoveries (precise to 10’) in Québec at thebeginning (1970–1979, A; n = 617) and at the end (1995-2001, B; n = 1,565) of the study. Thesecond period included the spring hunt in Québec (1998–2001).

J. Wildl. Manage. 69(2):2005 567HETEROGENEITY OF GREATER SNOW GOOSE HARVEST • Calvert et al.

harvest, especially during 1998–2001 (Fig. 6). Theage*time effect could not be interpreted withband recoveries because in some periods, virtual-ly no young were banded.

Overall, there were few indications of sex-relateddifferences in harvest. The factor sex and the inter-action age*sex were present in the best model onlyin the Canada/United States direct band recover-

ies and the United States band recoveries datasets(Table 1). In the country comparison, juvenilerecoveries showed very similar proportions of eachsex (51.1% females), while for adults more femaleswere recovered (57.4%) than males. For UnitedStates recoveries, the differences were small; males(52.3%) were represented slightly more than fe-males among juveniles and females (54.3%) more

frequently among adults.

Comparison ofRegular-Season and ConservationHarvests

Analyses of recoveriesduring years with a springharvest (1998–2001) inQuébec provided noindication that geograph-ic harvest distribution dif-fered between fall andspring (the region*sea-son interaction was notpresent in the bestmodel; Table 1; Σ ωAICc= 0.016). There was,however, evidence thatthe representation ofage groups in the har-vest differed between

Fig. 4. Distribution of greater snow goose band recoveries (precise to 10’) in the Atlantic Flyway states at the beginning(1975–1979, A; n = 239) and the end (1995–2001, B; n = 1,823) of the study (note that hunting only opened in 1975).

Fig. 5. Proportional representation of age classes in the harvest, by region, for direct bandrecoveries of greater snow geese in Québec, 1970–2001 (n = 1,734) and for the wholeAtlantic Flyway (n = 845). Circle size is proportional to sample size on a logarithmic scale.

J. Wildl. Manage. 69(2):2005568 HETEROGENEITY OF GREATER SNOW GOOSE HARVEST • Calvert et al.

the spring and fall sea-sons (the age*seasoninteraction was presentin the best model; Table1; Σ ωAICc = 0.925), witha much higher propor-tion of adults in thespring (59%) than in thefall recoveries (34%).

Harvest RatesIn the mid-1980s, the

harvest rate of GSG de-creased abruptly andremained relatively lowuntil the late 1990s (har-vest rate for 1975–1983and 1984–1997, 0.112 ±0.011 [SE] vs. 0.066 ±0.007 for adults and 0.719± 0.060 vs. 0.351 ± 0.033for juveniles, respective-ly). After the instaura-tion of spring harvestand liberalized regula-tions in 1998, harvestrate increased in adults but not juveniles; for1998–2001, harvest rate was estimated at 0.132 ±0.006 for adults (t = 5.00, df = 16, P < 0.001; compar-ison with the previous period, 1984–1997) and 0.396± 0.047 for juveniles (t = 0.67, df = 16, P = 0.512).

DISCUSSION

Spatial Heterogeneity of Harvest Distribution The GSG harvest increased in 1975 with the

opening of the hunt in the AF states, and the result-ing combined Canadian and United States harvestwas apparently sufficient to stop the populationgrowth for close to a decade (Reed 1990, Gauthierand Brault 1998, Menu et al. 2002). However, anabrupt drop in harvest rate occurred in the mid-1980s despite liberal harvest regulations, and thepopulation began a phase of rapid growth thatcontinued throughout the 1990s (Reed et al.1998). Spatial variation of waterfowl harvest is dif-ficult to analyze (Royle and Dubovsky 2001), butMenu et al. (2002) hypothesized that a change inthe migratory route and habitat use of geese, par-ticularly in Québec, might explain this suddendecline in harvest rate.

Over 3 decades, we detected a gradual spread-ing in the reported harvest in Québec from thecentral region of the St. Lawrence estuary toward

the southwestern area of the province (Lac St-Pierre and along the Québec-United States bor-der). This closely followed the observed changesin staging distribution of geese during the periodof population growth and the increased use ofagricultural fields for feeding during fall, partic-ularly in southwestern Québec (Filion et al. 1998,Reed et al. 1998). This expansion of the distribu-tion was associated with an increase in the pro-portion of the population using areas outside theupper estuary (Olson 2001), the region tradition-ally used by snow goose sport hunters (Freemarkand Cooch 1978), and may have been amplifiedby the spring conservation harvest beginning in1999 (Béchet et al. 2003). However, the Québecharvest distribution changes we noted have beenoccurring slowly since 1970 with no sudden shifts,and thus they cannot fully explain the suddenharvest rate decline in the mid-1980s.

We also observed alteration in the spatial har-vest distribution on wintering grounds in the AFstates that was characterized by a major northwardshift in the mid-1980s and a concentration of theharvest in mid-AF states. The observed redistribu-tion of the winter harvest appeared to be associat-ed with changes in geese migratory behavior andmay partially explain the decline in harvest rate inthe 1980s. The northerly shift in harvest paral-

Fig. 6. Proportional representation of age classes in the greater snow goose fall harvest inQuébec, 1970–2001, based on returns of goose tails as part of the Canadian Wildlife ServiceSpecies Composition Survey (total n = 9,739).

J. Wildl. Manage. 69(2):2005 569HETEROGENEITY OF GREATER SNOW GOOSE HARVEST • Calvert et al.

leled a similar shift in snow goose wintering dis-tribution revealed in the mid-winter counts, wherenumbers in the south decreased slightly while thenumbers in New Jersey, Delaware, and Maryland in-creased dramatically (Reed et al. 1998). This changein wintering distribution could be due to short-stop-ping, where the distance travelled southward isshortened over time in favor of remaining furthernorth, as has been observed in LSG (Alisauskas1998). Such changes in wintering location in otherspecies have been associated with changes in refugeand food availability (Malecki et al. 1988, Abrahamand Jefferies 1997, Hill and Frederick 1997), popu-lation size (Williams and Bishop 1990, Alisauskas1998), or temperatures (Hestbeck et al. 1991,Clausen et al. 1998). In GSG, distributional shiftsmay be related to the greater availability of cornfields in mid-AF states than further south in recentdecades and to increasing temperatures throughoutthe wintering grounds (Gauthier et al. 2004).

The shift in winter distribution of GSG likely hadseveral consequences for the harvest. First, by win-tering in mid-AF states, geese were exposed to asmaller pool of hunters than in the past when theycontinued through this area to southern AF states.Second, since the 1970s, permit sales in northernAF states declined by almost 50%, and sales in mid-AF states have declined since the mid-1980s, whilesouthern AF sales remained stable (Serie 1996;Martin and Padding 1999, 2000, 2001, 2002; Boydet al. 2002). Thus, the high density of geese nowwintering in mid-AF states may have swamped ashrinking pool of hunters (i.e., the relative huntingpressure decreased as an increasing number ofgeese faced a diminishing number of hunters), asis the case in ecological predator swamping(Hamilton 1971). It is also possible that thesechanges in hunting effort may have further con-tributed to the northerly shift during winter, al-though we know of no evidence to this effect.Third, because mid-AF states have a strong tradi-tion of hunting Canada geese, interest in snowgoose hunting may have been limited (e.g., therewas little increase in GSG kill in this area between1995 and 1998 during the Canada goose harvestclosure; J. Kelley, USFWS, personal communica-tion). Consequently, although GSG harvest in-creased in Canada during the period of populationgrowth of the 1980s and 1990s, no parallel increasewas noted for the AF (Reed et al. 1998). Thus,while the harvest rate remained relatively stablein Canada, it was decreasing in the United States.

We therefore suggest that the shifts in harvestdistribution and the ensuing decline in harvest

rate observed in the mid-1980s may be explainedby the collective effects of a sudden northerlyshift in the wintering distribution of snow geeseand declining hunter effort in areas they nowoccupy, possibly in combination with other distri-butional changes on staging areas in Québec.

Spatiotemporal Variation of HarvestComposition

We found that the overall proportion of juve-niles in the harvest within a given year was great-est in the areas reached earliest on the fall migra-tion. It was suggested that juveniles are moresusceptible to hunting mortality than adults, espe-cially early in their exposure to hunters (Prevettand MacInnes 1980, Francis et al. 1992b). Thechange we observed in age representation withinthe fall hunting season was consistent with thishypothesis, and it may be due to a rapid learningcurve of juveniles. Repeated experience withhunters likely influences the behaviour of geesethat quickly learn to avoid risky areas such as theedges of refuges (Giroux and Bédard 1986, Foxand Madsen 1997) or learn to fly and feed in larg-er groups (Prevett and MacInnes 1980). Reduc-tion in the number of juveniles in the fall flightdue to a high early fall hunting mortality alsoresults in fewer of these individuals being avail-able for hunters in regions reached later on themigration, and those remaining in the popula-tion would by then likely be less vulnerable (Vander Jeugd and Larsson 1998, Lemoine 2003,Calvert and Gauthier 2005).

Menu et al. (2002) found no differences in recov-ery rates between sexes in leg-banded adults in thispopulation, but the higher proportion of adultfemale recoveries we detected may be due to theuse of neck-collars almost exclusively in femalessince 1990 (Menu et al. 2000). While collars do notaffect survival of GSG (Menu et al. 2000, Reed2003), collared birds are generally characterized bya higher reporting rate than those wearing only ametal leg-band (Samuel et al. 1990, Castelli andTrost 1996, Schmutz and Morse 2000, Menu et al.2002). The larger proportion of adult femalesrecovered compared to males in the United Statesand the total North American recoveries data setscould therefore be a reflection of a higher report-ing rate. The higher proportion of females indirect recoveries might also be explained becausenewly banded geese are predominantly successfulbreeders (Reed et al. 2003), and females withjuveniles may experience elevated hunting vul-nerability (Giroux and Bédard 1986).

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Effects of Recent Changes in Regulationson Harvest Composition and Distribution

The implementation of conservation measuresin 1998 was associated with an increase in totalharvest rates, as well as changes in the harvestcomposition. The main difference between theregular and conservation harvests in Québec wasa much higher proportion of adults killed in thespring than in the fall. The spring harvest wasintroduced with the intention of reducing adultsurvival, the parameter to which populationgrowth rate was most sensitive (Gauthier andBrault 1998), and the predominance of adults inthe spring harvest implies that the conservationmeasures were working toward this goal. Wefound no difference in the geographic distribu-tion of spring and fall harvests even thoughspring and fall staging distributions of geese inQuébec were not identical (Reed et al. 1998).This suggests that hunter activities may be similarbetween the 2 seasons and was supported by CWSdata indicating that 79–88% of the spring permitholders each year were those who had purchasedpermits for the previous fall (B. Collins, CWS,unpublished data).

At the same time as the spring conservation har-vest was implemented, regulations were also lib-eralized for the fall and, to a lesser extent, winterhunts (CWS Waterfowl Committee 2001b). Tailreturn data, which were restricted to the fall sea-son, were useful in examining changes in theQuébec fall harvest caused by these regulationchanges. The spatial distribution of the harvestduring 1998–2001 was similar to previous years,with a further proportional decline in estuaryharvest. However, the proportion of adults in thefall harvest was highest during this period, fol-lowing a general rising trend. High adult kill inrecent years may have been partially due to theincreased representation of the Lac St-Pierre andborder regions in the harvest where juveniles maybe less vulnerable and less available than else-where in Québec. In addition, relaxed fall regu-lations since 1999 that allowed the use of baiting,electronic calls, and stalking techniques (CWSWaterfowl Committee 2001a,b) may have increasedthe adult kill, as observed in the spring harvest. Incontrast, we found no evidence for changes ingeographical or age distribution of the AF har-vest for 1998–2001 relative to previous years.

Validity of Data Used for AnalysesBand recoveries and harvest surveys are key

sources of data for waterfowl studies, but poten-

tial biases are not always considered. Our use ofparallel data sets allowed for their cross-valida-tion and provided more robust inferences than ifwe had relied on only 1 data source. Cooke et al.(2000) also made use of band-recovery and NHSdata, and found that band recoveries resulted inlower harvest rate estimates than those obtainedfrom survey data; these results were likely due tobiases in survey responses, population size esti-mates, or band-reporting rates. Survey data, suchas the goose tail returns of the SCS used in ouranalyses, were of unknown precision and may beprone to biases because they relied on huntersproperly reporting their kill, and non-responsebias or inaccurate responses may be a problem(Filion 1981, Barker 1991, Lemoine 2003). Per-haps even more critical was the dependency ofband recoveries on reporting rate. Our conclu-sions drawn from band-recovery data make theassumption that variation in band-reporting ratewas not the cause of observed patterns. For in-stance, GSG reporting rates may have increasedin recent years due to heightened public aware-ness, band solicitation, and the introduction of toll-free-number bands in 1995 (J. Dubovsky, USFWS,personal communication). Reporting rates alsomay vary among regions; in particular, ratesmight be higher in the AF states because Frenchis the predominant language in Québec, andband inscriptions are in English. This possibilityis supported by the fact that the majority of bandsreported in 1975–1979 and 1985–1989 came fromAF states, even though the Canadian harvest waslarger than the United States harvest in virtuallyall years based on survey data (Reed et al. 1998).

While these factors could have influenced ouranalyses, they were unlikely to have affected theinteractions we examined (e.g., presumably anyregional differences in reporting rate did notchange over time, and temporal changes inreporting rate were consistent among regionsand age-sex groups). Moreover, we found thatband recoveries and tail returns indicated thesame overall tendencies for the Canadian har-vest, implying that any biases in the data sets wereminor and did not affect our general inferences.

MANAGEMENT IMPLICATIONSThe special conservation measures introduced

in 1998 to control the GSG population were seenas temporary (K. M. Dickson, CWS, personal com-munication). We suggest that if sufficient harvestis to be maintained to prevent further populationgrowth once the spring conservation harvest is

J. Wildl. Manage. 69(2):2005 571HETEROGENEITY OF GREATER SNOW GOOSE HARVEST • Calvert et al.

closed, agencies should focus their efforts onencouraging increased hunting in mid-AF states,the area in which harvest did not keep pace withincreases in population size during the 1980s and1990s. Our results suggest that Delaware, Mary-land, New Jersey, and Pennsylvania are now stateswhere the potential for increased GSG harvestduring winter should be the greatest.

ACKNOWLEDGMENTSFunding was provided by a Natural Sciences

and Engineering Research Council of Canada(NSERC) grant to G. Gauthier, the Arctic GooseJoint Venture (Canadian Wildlife Service), theFonds pour la Formation des Chercheurs etl’Aide à la Recherche (FCAR, Ministère de l’Édu-cation du Québec), and the Department of Indi-an and Northern Affairs Canada. Logistic sup-port for banding was generously provided by thePolar Continental Shelf Project (PCSP, NaturalResources Canada). The Hunters and TrappersAssociation of Pond Inlet, Nunavut Territory,kindly offered assistance and support. A. M.Calvert was supported by a NSERC post-graduatescholarship. The early banding conducted by J.D. Heyland was very useful in examining long-term trends. We are grateful to all those who con-tributed to fieldwork over the years, in particularG. Picard. Additional data and assistance wereoffered by P. Brousseau, M. Melançon, and S.Turgeon of the Canadian Wildlife Service, and J.Dubovsky, J. Kelley, T. Nichols, and J. Serie of theU.S. Fish and Wildlife Service. Helpful commentson previous drafts were made by D. Fraser, E.Reed, K. Dickson, and J. Dubovsky. This is contri-bution no. 025-04 of PCSP.

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Associate Editor: Guliano.