a Danish action plan on pink-footed geese

Transcription

1 Ecology , Reducing wounding of game by shotgun hunting: effects of Blackwell Publishing Ltd a Danish action plan on pink-footed geese HENNING NOER*, JESPER MADSEN and POUL HARTMANN* *National Environmental Research Institute, Aarhus University, Department of Wildlife Ecology and Biodiversity, Kalø, Grenåvej 14, DK-8410 Rønde, Denmark; and National Environmental Research Institute, Aarhus University, Department of Arctic Environment, PO Box 358, Frederiksborgvej 399, DK-4000 Roskilde, Denmark Summary 1. Shooting of game by shotgun inevitably leads to wounding of some individuals. Few attempts, however, have been made to quantify the numbers involved. Following demonstration that for certain species nearly one bird was wounded for every one killed, a national action plan to reduce wounding of game was implemented in Denmark in The plan called for substantial improvements in hunting practice to reduce the number of wounded birds, granting hunters an initial period to achieve this on a voluntary basis. 2. The Svalbard pink-footed goose is hunted exclusively in Norway and in Denmark, where two-thirds of the annual harvest is taken. Before 1997, 25% of the first-year and 36% of the older geese carried embedded shot, corresponding to at least 0 7 wounded geese per bagged one. We studied the effects of the action plan by X-raying annual catches of geese during Since 1998 there has been a significant decrease in the proportion of geese carrying shot for both first-years (7 11% in catches) and older geese (gradual decrease to c. 18% by 2005). A simple population dynamic model predicts these decreases to be consistent with a c. 60% reduction of numbers wounded for both age classes. 4. During the Svalbard pink-footed goose population increased from to individuals. Information on harvest size is sparse, and the possibility that declining harvest rates could have affected the proportion of geese carrying shot cannot be disregarded. We show that the observed decreases cannot be explained solely by decreasing harvest rates, although calculated effects of the plan may have been somewhat inflated. Even in that case, however, reductions of at least 50% appear to have resulted from the plan. 5. Synthesis and applications. The basic remedial action to reduce wounding has been to encourage compliance with the 25 m maximum range recommended for shooting geese in Denmark. This reduction in range eliminates shots that have a low probability of killing and a relatively high risk of wounding. Since 1997, the total annual number of harvested geese in Denmark has increased from to Thus, reductions in numbers wounded do not appear to have had any negative impact on harvest size. Key-words: Anser brachyrhynchus, crippling, embedded shot, hunting, management, pink-footed goose, wounding Ecology (2007) 44, doi: /j x Introduction Ecological Society Correspondence: Henning Noer, National Environmental Research Institute, Aarhus University, Department of Wildlife Ecology and Biodiversity, Kalø, Grenåvej 14, DK-8410 Rønde, Denmark (fax: ; hn@dmu.dk). Hunting is a common recreational activity in many countries, and each autumn millions of individuals of many species of game are harvested. Even in a small country such as Denmark ( km 2 ), hunting licence holders harvest over 2 million individuals of more than 40 game species annually (Bregnballe et al. 2003).

2 654 H. Noer et al. Hunting has often been a subject of debate, and has attracted much management effort, most of which has been focused upon the influence of harvest on population sizes (e.g. Nichols, Johnson & Williams 1995; Sutherland 2001; Menu, Gauthier & Reed 2002; Calvert & Gauthier 2005) or on the effects of disturbance on distributions and foraging efficiencies of staging and wintering individuals (e.g. Fox & Madsen 1997; Madsen 1998a,b; Béchet, Giroux & Gauthier 2004). In comparison, some other problems associated with hunting seem to have attracted less attention. One of these problems is the risk of wounding associated with shotgun hunting. Evidence that substantial numbers of birds may be wounded some time during their life-span has been in existence for many years. For species of geese, 28 62% of X-rayed individuals have been found to contain embedded shot (Elder 1950, 1955a,b; Grieb 1970; Norman 1976; Jönsson, Karlsson & Svenson 1985; Noer & Madsen 1996), while for sea ducks proportions of 25 35% have been reported (Noer et al. 1996; Hicklin & Barrow 2004; Falk et al. 2006). For the Svalbard pink-footed goose Anser brachyrhynchus, Noer & Madsen (1996) found that 25% of the first-years carried embedded shot after surviving one hunting season, while 36% of the older geese carried shot. For a long-lived species, of course, small annual numbers wounded and surviving with embedded shot may eventually accumulate into large percentages, but by means of a simple theoretical model it was shown that these percentages, when corrected for a lower survival of individuals carrying shot, corresponded to infliction of pellets upon c. 7% of the adult population annually (Madsen & Noer 1996). Not all woundings are detected by X-ray examinations, and we use the term infliction rate, defined as the proportion of the adult population that is wounded and survives with embedded shot each year, in order to prevent proportions with embedded shot from being taken to represent total numbers wounded. Annual harvest rates for this species were assessed to c. 10% of the population (Noer & Madsen 1996). Therefore, the results implied that shot were inflicted upon at least 0 7 geese for each individual that was killed (Madsen & Noer 1996). To this figure should be added an unknown but not insubstantial proportion of seriously wounded individuals that do not recover, probably bringing the total wounding rate closer to 1 per killed goose. As both the proportions carrying shot and survival rates are similar to results from other goose species and populations (Elder 1955a; Grieb 1970; Ankney 1975; Jönsson et al. 1985; Madsen, Cracknell & Fox 1999), comparable rates of wounding might presumably also be found in other hunted goose species. These findings made wounding of game an issue in Denmark. The Danish Game Act states explicitly that management of hunting shall be based on a wise use concept, including ethical as well as ecological principles, and that hunters must not inflict unnecessary suffering upon game. As it must be possible to hunt in ways that result in lower risks of wounding, rates such as those observed were definitely not in compliance with the statements and intentions of the Act. In 1997, an action plan to reduce the degree of wounding caused by shotgun hunting was proposed by the Danish Council for Wildlife Management (a board composed of both hunting and non-hunting organizations, charged with giving recommendations to the Minister of the Environment). This plan was endorsed officially before the start of the 1997/98 hunting season, and thus appears to be the first attempt ever made to reduce wounding on a comprehensive scale. Hunters were granted an initial period to reduce wounding on a voluntary basis, the main remedial action being to comply with the maximum range of 25 m recommended for goose shooting. If major reductions of numbers wounded did not result, the plan stated further that limiting hunting opportunities and, in the final resort, protection might be the only realistic way to achieve improvements. Thus, serious management decisions hinge on the outcome, and monitoring of the effects was in demand. The number of species suited to this type of monitoring is, however, limited. Most species hunted in Denmark are migratory waterfowl, hunted in several other countries, and of the relatively few resident species all but the red fox Vulpes vulpes have low proportions with shot (Noer, Hartmann & Madsen 2006 and references therein). Since 1998 we have monitored common eider Somateria mollissima, red fox and pink-footed goose by means of X-raying samples on a more or less annual basis in order to assess the effects of the plan. The purpose of this paper is to assess the extent to which voluntary changes in hunter behaviour succeeded in reducing wounding rates in pink-footed geese, present a simple model used to assess infliction rates from proportions with shot detected by X-ray examination, and discuss the issues associated with implementing these changes in Denmark and elsewhere. During the study period, interpretation of the results has been complicated further by rapid growth of the population. Data on numbers of pink-footed geese harvested in Denmark are sparse, and the possibility that harvest rates have decreased since 1997 cannot be disregarded. Decreasing harvest rates will also cause the proportions with embedded shot to decrease, and the question of to what extent decreasing proportions with shot reflect improvements in hunting performance has become pertinent. For this reason, we also examine the robustness of the conclusions in relation to varying harvest and survival rates. Materials and methods the svalbard pink-footed goose population The Svalbard pink-footed goose breeds exclusively in Svalbard and winters in Denmark, the Netherlands

3 655 Reduced wounding of pink-footed geese and Belgium (Madsen et al. 1999). In spring and autumn the geese stage in western Denmark and Norway. Autumn arrival in Denmark is September, when birds stage for 3 6 weeks before continuing migration. In mild winters, return flights to Denmark take place from early December. The population numbered individuals in the 1960s and has been growing since In the mid-1990s, were recorded by annual November census counts and the population grew slowly, at an annual rate of c. 1% (Noer & Madsen 1996; Madsen et al. 1999). Since 1997 the growth rate has increased, and in geese were counted (J. Madsen unpublished). This corresponds to an average annual growth rate of 4 28% during Spring hunting in Svalbard was banned in 1975, and the species was protected in the Netherlands in 1976, in Germany in 1977 and in Belgium in Since 1981, this population has thus been hunted only in Denmark and Norway. It is likely that this protection made an important contribution to the population growth (Madsen et al. 1999). In Denmark, shooting of pink-footed geese is typically carried out over decoys, when geese forage in fields, or on daily flights to and from nocturnal roosts. Information on numbers bagged is sparse. Geese are pooled in Danish bag statistics, and five species have an open season. Total numbers of harvested geese increased from in 1995 to in 2004, but undoubtedly most of this increase concerns greylag goose Anser anser and Canada goose Branta canadensis. Surveys of wings of bagged waterfowl have been conducted since 1982 (Clausager 2004 and references therein). Both annual numbers of pink-footed goose wings and their proportion of the total number of goose wings received increased markedly Noer & Madsen (1996) assessed the annual harvest to be c first-year and 2000 older geese, of which two-thirds were killed in Denmark and one-third in Norway, including c. 300 on Svalbard. In 2004 the first firm estimate, based on augmented wing surveys, was possible, comprising 2300 harvested in Denmark in that year (T. K. Christensen, personal communication). From this we infer that annual numbers of harvested pink-footed geese have not decreased, but may have ranged between constant and increasing in proportion to the population size. Harvest rates, therefore, may have ranged between declining in inverse proportion to the population size and being constant. X-rays of geese from 1990 to 1992 showed that 36 0% of the adults and 24 6% of the first-years carried embedded shot (Noer & Madsen 1996). Annual variation was small (20 26% for first-years and 35 37% for adults), and 36% of an additional sample of 58 adult geese collected for physiological analyses in spring 1996 also carried shot. Thus, we assume that proportions with shot were constant at the time of the start of the action plan. Because the plan focuses on reductions in numbers wounded, we use proportions with shot as a measure of effects of the plan. Survival rates were not analysed separately as part of the present analyses, but estimates are available from resightings (Madsen & Noer 1996; Noer & Madsen 1996; Madsen, Frederiksen & Ganter 2002; Kéry, Madsen & Lebreton 2006). In spite of comprehensive neck-banding/resighting protocols there is currently some uncertainty with respect to adult survival. Madsen et al. (2002) found a mean survival of for the period , but also a long-term trend, with survival decreasing from 0 90 to 0 79 between 1990 and In a reassessment of the data from 1990 to 2002 (Kéry et al. 2006) could find no evidence for a long-term trend, but estimated a significantly higher survival rate (0 967) during the first period after neck-banding, in contrast to for subsequent years. Pending clarification of these issues, we examined the sensitivity of our results by repeating calculations for survival rates ranging from (Noer & Madsen 1996) up to With an annual growth rate of c. 4% of the population, we consider these values to span the realistic regime. data collection and compilation All goose catches were made in late March (c. 3 months after the close of the hunting season) at Stadil Fjord, western Jutland, Denmark. Catches were performed by means of cannon net, after baiting with grain for a week. Annual totals of geese were caught. The geese can be assigned to two age classes: firstyear or older. First-year individuals lose their distinctive plumage during summer moult on the breeding grounds. Hence, a cohort examined as first-years in March will recruit into the group of older geese before the start of the following hunting season, and at the time of catching all cohorts of older geese will have experienced two or more hunting seasons. A mobile surgical X-ray unit with screen and printer was used for examinations during Records were screened for shot in the gizzard or oesophagus that could have been ingested rather than inflicted (Noer & Madsen 1996). All geese were neck-banded before release. predicted effects of the action plan A new cohort of first-years, having experienced only one hunting season, is investigated each year. Thus, reductions in numbers wounded should be reflected in a decrease in the proportion of first-years carrying shot taking effect already in For first-years, also, the proportion carrying shot equals the infliction rate, and any reduction can be assessed directly. Examination of first-years therefore seems to be the fastest and most efficient way to assess any effects of a plan. However, geese are long-lived, and the corresponding low proportion of young in the population

4 656 H. Noer et al. Fig. 1. The basis for calculating annual changes in proportions of adult geese with embedded shot. At sampling time t (a), the proportion of adult geese with shot was θ a,t, and the number of adults was close to its annual minimum size (the fraction surviving, φ). During summer moult (b), the size of the adult segment reaches its annual maximum (represented by a unit square) by recruitment of first-years with a proportion of carriers of shot θ j,t. For a stable population, the relative size of the recruiting segment will be 1 φ. Shot are inflicted upon a proportion π of the population during the following hunting season (c), while the next sample is taken at time t + 1 after mortality (d). Formulae for calculating the proportion of adults with shot at sampling time t + 1 from the proportions shown in a c are given in the text. causes sample sizes for first-years to be too small for statistical reliability, at least until several repeats are available. Much larger numbers of older geese are caught, but because of their longevity the proportion of carriers within this age group is expected to respond far more gradually to reductions of numbers wounded. We used a simple model with no annual variation in survival rates to predict effects of changes of infliction rates. The basic events affecting the proportion of adults with shot between two successive catches are shown in Fig. 1. For a given infliction rate π, the proportion of adult geese with embedded shot in a sample (θ a,t+1 ) is calculated from the proportion in the preceding year (θ a,t ), adult survival φ, and the proportion θ j with shot among recruiting first-years as: θ a,t+1 = (1 φ)[θ j,t + π (1 θ j,t )] + φ[θ a,t + π [1 θ a,t )] eqn 1 This model assumes that the proportion of firstyears with shot does not change during the 4 months between sampling and recruitment, but as mortality of immature birds will be small at that time of the year and there is no spring hunting, we consider this reasonable. However, eqn 1 also assumes that the probability of survival is the same for individuals both with and without embedded shot, and for pink-footed geese Madsen & Noer (1996) showed that survival of individuals with shot was significantly lower, namely φ c = and φ n = for carriers and non-carriers. While Noer & Madsen (1996) assumed that the presence of shot was directly linked to the increased mortality, recent analyses (Madsen & Riget in press) suggest that it is not wounding per se that causes lower subsequent survival. Rather, a segment of the population is more exposed to hunting through differential behaviour. Hence, we assume here that embedded shot do not cause lower survival, and that consequently mean adult survival φ is unaffected by the proportion carrying shot. This constrains survival of non-carriers to φ n = (φ θ a,t φ c )/(1 θ a,t ). Extending eqn 1 to comprise differential mortality, we assumed further that all mortality takes place after wounding by assigning survival probability φ c to all individuals carrying shot (see Fig. 1). We checked the effect of this by repeating the calculations for the alternative assumption (all mortality takes place between sampling and the start of the hunting season). Results never differed within the first three decimal points, and we consider this approximation valid. Given this, the frequency of carriers at sampling time t + 1 will be: θ a,t+1 = φ c {(1 φ)[θ j,t + π (1 θ j,t )] + φ[θ a,t + π (1 θ a,t )]}/φ eqn 2 Starting from the (assumed stable) situation when the action plan was implemented (t = 0), effects of the plan can be calculated for any changes in π (from its preplan value of 0 069) by using eqn 2 recursively. Because π depends on adult survival (Noer & Madsen 1996), its value was adjusted numerically for each input survival rate, to correspond to a constant proportion of carriers of if no reduction took place. The mean value of π during was estimated from the observed annual proportions by least-squares fitting of eqn 2. The simple models presented in eqns 1 and 2 thus pool sampling variation and annual variation in survival rates into residual variation in order to predict mean rates over a given time-span. If data giving annual survival and infliction rates are available, the expressions are easily generalised to comprise annual variation. Because the plan took effect in June 1997, it could not affect the proportion carrying shot in the cohort recruiting during that summer. Therefore, θ j = was used for calculating the expected proportion of geese with shot for There is no indication that the ratio of wounded to bagged geese differs between first-years and adults (Madsen & Noer 1996). Hence, calculations of adult infliction rates used only the preplan value for θ j (0 246) as input, while subsequent first-year proportions were calculated by adjusting this figure to correspond to the reduction of π found for

5 657 Reduced wounding of pink-footed geese adults. Thus, the observed proportions of first-year carriers after 1997 do not affect the estimated reduction for older geese, and hence the two sets of results can be compared for verification. predicted effects of decreasing harvest rates For a population with an annual rate of growth R, per capita recruitment will exceed mortality by R. This means that after recruitment and autumn hunting (see Fig. 1), the proportion of carriers will be {(1 φ + R) [θ j,t + π (1 θ j,t )] + φ [θ a,t + π (1 θ a,t )]}/(1 + R), and after differential mortality it will change to: θ a,t+1 = φ c {[(1 φ + R)(θ j,t + π (1 θ j,t )] + φ[θ a,t + π (1 θ a,t )]/(1 + R)}/φ eqn 3 Expected changes in proportions with shot resulting from population growth were calculated recursively (year by year) from eqn 3. If the action plan had no effects, the ratio of wounded to killed geese would remain unchanged, and any changes in π would be caused exclusively by changes in harvest rates. The corresponding annual proportions inflicted (π t ) could thus be calculated from any assumed harvest and population sizes and input in eqn 3. Combined effects of improved hunting performance and decreasing harvest rates could also be modelled from eqn 3 by reducing the value of π at t = 0, followed by further annual reductions resulting from decreasing harvest rates. Results proportions of individuals with embedded shot Catches were carried out annually between 1998 and 2005, except in A total of 349 first-year and 1555 older geese were X-rayed (Table 1). Although the same Table 1. Annual numbers of first-year and adult pink-footed geese caught and X-rayed in Stadil Fjord (pooled) and , together with percentages carrying embedded shot Year First-year Older n % n % Total before Total after site was used in all years, there were few recaptures (c. 1% of the sample), and up to geese were present at times of catches. Thus, the geese examined can be assumed to represent random sampling of the population. The 2005 catch was very large, and in order to limit handling time more than 100 adult geese were released without X-raying, while all first-years were examined. The proportion of first-year carriers decreased to 10 5% in 1998, and since that year has been consistently below 12% (Table 1). There was no significant temporal trend (Spearman s rank correlation coefficient (e.g. Sokal & Rohlf 1981), r s = 0 52, P > 0 05). Therefore, data for first-years were pooled to an overall proportion with shot of (Table 1). Comparison of pooled data before and after 1997 showed a highly significant difference [χ 2 = (with a Yates correction, e.g. Sokal & Rohlf (1981), d.f. = 1, P < 0 001]. The proportion of adult carriers decreased to 27 1% in the 1998 sample, and with minor annual fluctuations has subsequently decreased gradually to 17 8% by 2005 (Table 1). A significant temporal trend was found (r s = 0 86, P < 0 05), and pooled data before and after 1997 differed significantly (χ 2 = (with a Yates correction), d.f. = 1, P < ). predicted effects of the action plan The proportions of first-years with shot after 1997 lead to an estimated reduction of the annual infliction rate of 63%, from to (Table 1). Using the preplan proportion of first-year carriers θ j = 0 246, survival rates φ = and φ c = 0 779, and the preplan infliction rate of π = (Noer & Madsen 1996), the gradual decrease in the proportion of adult carriers could be well fitted by the model resulting from eqn 2 (Fig. 2a). A slight numerical change of π (to ) was necessary in order to adjust the preplan value to the assumption that pellets do not cause increased mortality. Least-squares fitting of eqn 2 resulted in an estimated 61% reduction of the annual infliction rate (Fig. 2a). For comparison, calculations based on the slightly more conservative assumption that shot are the direct cause of increased mortality result in an estimated reduction of 60%. For the highest survival rate examined (φ = 0 897, corresponding to a survival φ n = of geese with no embedded shot), the preplan value of π was adjusted to a stable proportion of 0 36 (π = 0 049). Fitting of this function resulted in an estimated reduction of 72% (Fig. 2b). This indicates some sensitivity of the estimated decrease to survival, but also demonstrates that the higher the annual survival, the higher the estimated reduction. Selecting a survival rate from the lower part of the possible range is thus conservative in relation to assessing effects of the plan. For the basic version of the model (φ = 0 838, Fig. 2a), the proportion of juvenile carriers after start of the action plan is predicted to be (1 0 61) = 0 096,

6 658 H. Noer et al. Fig. 2. The proportions of adult pink-footed geese carrying shot observed before 1998 (pooled, t = 0), and in subsequent catches. For mean adult survival φ = (a), the estimated reduction of the proportion inflicted with shot each year is 61% (bold line). For mean adult survival φ = (b), the corresponding estimate is 72% (bold line). Expected proportions carrying shot resulting from reductions of, respectively (top to bottom) 0%, 25%, 50%, 75% and 100% of the annual infliction rate (the latter corresponding to protection) are shown for comparison. Fig. 3. The proportions of first-year (a) and older (b) pinkfooted geese carrying shot observed before 1998 (pooled, t = 0) and in subsequent catches, compared to expected proportions resulting from decreasing harvest rates. Annual per capita growth rate is R = 4 28% and mean adult survival φ = In both diagrams, changes in proportions carrying shot are shown for harvested numbers having, respectively, increased 4 28% (top), 3 21%, 2 14%, 1 07% and 0% (bottom) annually. which is close to the actually observed (Table 1). From the model assuming φ = 0 898, however, this assumption would result in an expected proportion of (1 0 72) = Although not significantly different from the observed numbers (χ 2 = 2 80, d.f. = 1, 0 05 < P < 0 10), this value clearly gives a poorer fit to the data. We conclude from these results that the observed changes in proportions of both first-years and adults with shot can be explained adequately by assuming that the changes were caused by effects of the action plan. effects of decreasing harvest rates We modelled the effects of decreasing harvest rates by assuming a stable population before 1997, and an annual growth rate of 4 28% Harvest rates were assumed to vary between a constant annual harvest of 3000 individuals and an annual increase in harvest of 4 28% after 1997 (i.e. a constant harvest rate). The influence of survival rates was examined for values ranging from to Even for a constant bag size, the decrease in the proportions carrying shot predicted to result from decreasing harvest rates were much more gradual than the values actually observed (Fig. 3). Sensitivity to φ was small, results for φ = (not shown) being very similar, although the higher the survival rate, the slower the decrease in proportion with shot (i.e. the greater the discrepancy between predicted and observed values). We checked this further by varying the preplan value of π within the confidence limits derived by Noer & Madsen (1996). This did not change the conclusions, either. The population growth was not necessarily gradual, but could have resulted from large increments in some years. In particular, the large decrease found in 1998 might be interesting as counts suggested particularly large population increases during and the preplan samples did not include The possibility that the low proportion (0 271) of adults carrying shot in the 1998 sample might be the outcome of 2 consecutive years of rapid population growth and low harvest rates was examined by repeating the calculations for starting values of θ j down to (corresponding to c wounded out of an unusually large cohort of 8000 firstyears). The results showed that there is some sensitivity of the calculated reduction of numbers wounded to the proportions in 1997, and that in a worst possible scenario the reduction might be c. 50% instead of 61%. These calculations also showed that even in the case of a very large cohort with a low percentage of carriers

7 659 Reduced wounding of pink-footed geese recruiting during the summer of 1996, this could hardly decrease the proportion of adult carriers below by Starting with that value, further recruitment of a large cohort in the summer of 1997 could only approximate the observed 1998 proportions if no wounding took place during the autumn of 1997 a highly unlikely assumption, as wing surveys from that season comprised normal numbers of pink-footed goose wings. From these calculations, we consider the assumption of proportions of and in 1997 to be fairly well justified. We cannot explain the low proportion of adults carrying shot in the 1998 sample, but we note that this value has little effect on the reduction estimated from least-squares fitting, because the resulting curve is constrained to a value of in March Exclusion of this value from the fitting changes the estimated reduction only from 61% to 60% of the preplan value of π. We therefore conclude that the observed changes in proportions of individuals with embedded shot cannot be explained solely by population growth. Note that for a constant harvest rate (Fig. 3) there would be no change in the proportions with embedded shot (except a very minor decrease during the first few years after start of growth). combined effects of the plan and decreasing harvest rates Effects of reductions of numbers wounded and population growth are not mutually exclusive. Although a declining harvest rate cannot solely explain the observed reduction, it might still influence the interpretation by inflating the estimated reduction. We assessed the sensitivity of the estimated reduction to a declining harvest rate by repeating the calculations for various scenarios combining the two sets of models. The most conservative of these scenarios assumed a constant harvest (cp. Fig. 3). For both firstyears (Fig. 4a) and older geese (Fig. 4b), the data could be fitted by a reduction of c. 50% in infliction rate, corresponding to the findings for a stepwise increase of population size discussed above. Considering this a worst possible case scenario, however, we note that the impact on the estimated reduction is relatively modest, decreasing the figure from 61% (Fig. 2a) to c. 50% (Fig. 5b). We also note that the resulting reduction of c. 50% is very similar to the effects of stepwise population growth in discussed above. Discussion effects of the action plan Apart from the possibility that population growth and declining harvest rates affected the proportions of geese carrying shot, we have been unable to find other explanations for the observed decreases. For the two Fig. 4. The proportions of first-year (a) and adult (b) pinkfooted geese carrying shot observed before 1998 (pooled, t = 0) and in subsequent catches, compared to expected proportions resulting from combined effects of the action plan and decreasing harvest rates for constant annual numbers killed. Annual per capita growth rate is R = 4 28% and adult survival φ = For both first-years and adults, the estimated reduction in the proportion inflicted with shot each year was c. 49% (solid lines). For comparison, expected changes are shown for, respectively (top down) 0%, 25%, 50%, 75% and 100% decreases of the annual infliction rate. other species monitored, the 25% of foxes observed initially to be carrying shot (age classes pooled) had decreased significantly to 10% by 2005 (Noer et al. 2006), while a significant decrease from 34% to 28% between 1996 and 2001 was found for eider females (Noer et al. 2006). Based on this, we contend that reductions in the numbers of geese inflicted annually since 1997 almost certainly caused the observed decreases of proportions with embedded shot. The model used for predicting infliction rates from proportions with shot rests on a number of simplifications. Undoubtedly, there will be some annual variation in survival and harvest rates, and a model with constant rates will only represent mean values. Survival rates of pink-footed geese, however, are relatively high and show little annual variation (Kéry et al. 2006), and inspection of Figs 2 4 suggests a fairly good fit of the predicted proportions to the data. Based on this, we consider the predicted proportions likely to represent a good approximation to reality. That the calculated rates are realistic is supported further by field recordings. Shooting of mallards Anas platyrhynchos in an experimental set-up where hunters of varying experience participated resulted in an overall rate of 0 6 wounded per bagged duck, while shooting of

8 660 H. Noer et al. eiders performed by highly experienced hunters under optimal conditions resulted in c. 0 2 wounded per bagged (Noer et al. 2006). These figures compare fairly well to rates calculated from data resulting from X-ray studies before and after A number of earlier studies conducted in order to compare lead and steel shot in the United States also suggest that the calculated rates are reasonably realistic (Anderson & Sanderson 1979; Homburg et al. 1982). According to the calculations, the minimum reduction of numbers wounded resulting from the action plan was c. 50%. In addition to the harvest taken in Denmark, the Svalbard pink-footed goose is also hunted in Norway, where there has been no corresponding debate and no plan has been implemented. Thus, the possibility remains that reductions in numbers of wounded geese have taken place exclusively in Denmark, in which case improvements may be considerably better than 50%. The action plan s call for a major reduction therefore appears to have been met. total numbers wounded X-ray investigations will neither detect geese hit without shot being embedded in their body tissues nor seriously wounded individuals that do not survive until the spring catches. The calculated infliction rates will therefore reflect only part of the total numbers wounded. Bellrose (1953) examined 700 mallards and black ducks A. rubripes killed by shot. Of these, 6% did not contain embedded shot. We consider this to indicate that the proportion of geese being hit and surviving without embedded shot is probably too small to have affected the conclusions. Seriously wounded geese, not surviving until catches, almost certainly make up a larger proportion of the total numbers wounded. For mallards, Bellrose (1953) estimated that seriously wounded birds comprised c. 50% of those lightly wounded and surviving with embedded shot. Few of these seriously wounded mallards recover (Bellrose 1953; van Dyke 1981), and if numbers of seriously wounded geese compare to this figure the rates of infliction given above may comprise less than 70% of the total wounding (Noer et al. 1996, 2006). Although we have no direct knowledge of how the observed reductions were achieved, direct observations of pink-footed goose shooting in western Jutland during showed that an average of eight shots were expended per bagged goose, and more often than not that range exceeded 25 m, with ranges up to m being observed regularly (Noer et al. 2006). Thus, a general decrease of range the main remedial action recommended by the plan is by far the most probable cause of the reductions in numbers of wounded geese. A number of studies carried out in the United States in the 1970s in order to compare lead and steel shot are available for assessing the impact of range on the risk of serious wounding. In studies for which range has been observed as a covariate, the overall proportion of geese or ducks hit to those killed almost invariably decreases with increasing range (e.g. Anderson & Sanderson 1979; Homburg et al. 1982). In a recent study of common eider hunting, including figures for both seriously and lightly wounded birds, the probability that a shot hitting the bird resulted in an instant kill decreased with range, to near zero for ranges above 40 m (Noer et al. 2006). Thus, all available evidence indicates that if numbers of lightly wounded geese are reduced by a general decrease of range, numbers of seriously wounded birds will also decrease. implications for management The risk of wounding by shotgun hunting may be high, especially for larger species of game. The gains that can be made by inducing hunters to shoot more prudently may therefore be substantial. If comparable improvements have taken place for eiders, the other four huntable goose species and red foxes, the effects of the action plan may have prevented up to annual woundings of these seven species in Denmark (Noer et al. 2006). The plan and its results concern ethical rather than ecological aspects of hunting. Management policies on ethics may differ between countries, but in Denmark ethics are an explicitly stated part of the Game Act, and the public debate resulting from publication of the preplan wounding rates (Noer et al. 1996) left no doubt that such rates were unacceptable not only to the 96% non-hunting members of the community, but certainly also to many hunters. In Denmark, 12-gauge shotguns and 4 0 mm shot are the largest permitted calibre and shot size. A final ban on lead shot took effect in 1996, but lead had been gradually phased out since 1981, and use of lead shot had been banned in wetland reserves (including those where pink-footed geese occur) since The Game Act is augmented by a specific and written code of conduct for hunters, and prospective hunters have to know this code in order to pass the test mandatory for obtaining a hunting licence. For goose hunting, recommendations are that geese should not be shot at when the distance from the hunter to the quarry exceeds 25 m, and that a maximum of three shots should be expended per bagged goose. Shooting efficiency of individual hunters is, of course, variable, and undoubtedly some hunters can shoot efficiently at ranges above 25 m. Both good and poor shooters, however, have a decreasing probability of hitting accurately with increasing range. For the individual hunter, the recommended maximum range of 25 m can thus be viewed as adaptable, and shell expenditure, i.e. the number of shots expended per bagged goose, will be the most suitable indicator for risk of wounding (Noer et al. 2006). Details of weapons and ammunition may vary, and some adjustments of the recommendations may have to be made in accordance. The basic principles,

9 661 Reduced wounding of pink-footed geese however, do not vary. Thus, if the purpose of a hunter is to maximize harvest size, all shooting opportunities within ranges yielding a chance of killing should be exploited, regardless of the risk of wounding. If the purpose, however, is to reduce wounding, range and/or number of shots per bagged bird should be restricted. Because the probability of killing the game properly decreases with increasing range the penalty for doing this, measured in terms of numbers harvested, will, in nearly all cases, be modest. One main obstacle in achieving reductions has undoubtedly been to convince a sufficient number of hunters of these basic facts. Although from the outset the plan had strong official support from both hunting and non-hunting organisations, it was viewed with considerable and quite outspoken scepticism at the individual level. Many hunters felt that they were being charged with impossible demands that could only result in eventual reductions of hunting opportunities. However, as the proportion of geese carrying shot has decreased while the overall goose bag has continued to increase, the plan and its intentions have certainly gained wider support within the hunting community. In granting an initial period to achieve substantial reductions in numbers wounded on a voluntary basis, while suggesting that reductions of hunting opportunities may be eventually the only option, the action plan is a typical stick-and-carrot model. Information and educational campaigns carried out by both the Danish Forest and Nature Agency and the Danish Hunters Association have been important elements of the plan, and these efforts have been augmented by substantial public attention. In response to the latter, annual results of X-raying have been made publicly available by press releases shortly after sampling since There is evidence to suggest that public attention is decisive in making improvements; for example, substantial reductions in the proportions of foxes carrying shot were not observed until 2003, when lack of progress for this species became an issue, and an eventual ban on shotgun shooting of foxes was signalled by the Ministry of Environment (Noer et al. 2006). As a consequence, it should not be taken for granted that the observed improvements can be maintained without sustaining focus. A proper balance between harvest size and risk of wounding will, of course, always be a matter of debate. However, ethical and animal welfare aspects play an increasingly important role in many places, including Denmark. Given that the reductions have been achieved over a period when numbers of harvested geese doubled, in Denmark at least hunters and managers alike may find it problematic to defend high rates of wounding of game in the future. Acknowledgements Many volunteers have assisted in the annual catches. In particular Ebbe Bøgebjerg, NERI, expertly conducted the use of cannon net. The Danish Army kindly leant mobile equipment and other support to the studies from 1998 onwards. Thomas K. Christensen supplied additional information of wing surveys, and Anthony D. Fox, two anonymous referees and Jenny Gill gave helpful suggestions to the manuscript. We give our sincere thanks to all. References Anderson, W.L. & Sanderson, G.C. (1979) Effectiveness of steel shot in 3-inch, 12-gauge shells for hunting Canada geese. Wildlife Society Bulletin, 7, Ankney, C.D. (1975) Incidence and size of lead shot in lesser snow goose. Wildlife Society Bulletin, 3, Béchet, A., Giroux, J.-F. & Gauthier, G. 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