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Annex 3 Scientific research and monitoring

Index

3.1 Overview of the goose Population Viability Analyses
(Detailed individual population PVA information papers are published separately)
3.2 AEWA classifications and status of Scottish goose populations
3.3 Status and monitoring of goose populations in Scotland, including recommendations for future research, survey and monitoring work
3.4 Population sizes and trends for the main breeding and wintering populations of geese occurring in Scotland
3.5 Monitoring of aspects of Scottish goose populations: the adequacy of current monitoring and need for improvements over the next five years
3.6 Goose research, survey and monitoring needs: draft prioritised project list

3.1 Overview of the goose Population Viability Analyses

Greg Mudge ( SNH) and Ian Bainbridge ( SEERAD) on behalf of GSAG

This paper sets the context of the goose population viability analyses ( PVA) recently conducted by IoZ and WWT and summarises the key findings from the PVA Information Papers (published separately). It then goes on to draw out the policy implications of the PVA analyses, and provides scientific advice for goose conservation and management in Scotland. Advice on the future monitoring of these populations is contained in the separately published paper 'Status and Monitoring of goose populations in Scotland'.

Work carried out to date on Scottish wintering goose populations

SNH has, in conjunction with the Institute of Zoology, London and the Wildfowl and Wetlands Trust provided the newly revised results of PVAs on the five main wintering populations of geese of concern in relation to agriculture and conservation. These are:

• Iceland/Greenland population of pink-footed goose
• Greenland white-fronted goose
• Iceland population of greylag goose
• Greenland population of barnacle goose
• Svalbard population of barnacle goose

The analyses cover data provided for the period up to 2002 (greylag and pinkfoot) or 2003 (other species); so the figures used for population summaries do not necessarily reflect the most up-to-date population counts.

The information developed from the analyses is published separately:

Trinder, M., Rowcliffe, M., Pettifor, R., Rees, E., Griffin, L., Ogilvie, M. & Percival, S. (2005). Status and population viability analyses of geese in Scotland. Scottish Natural Heritage Commissioned Report F03 AC 302 .

The report comprises five detailed information papers and an explanatory guide to the modelling undertaken. It is available on the SNH website :

http://www.snh.org.uk/pdfs/publications/commreport/Status_and_Population_Viability_Analyses_of_geese_in_Scotland_16605.pdf

Background

The numbers of most animal populations change from year to year, and wintering geese are no exception. Reasons for such changes are many, but include variability in birth and death rates as well as other intrinsic factors. This uncertainty means that most species face the potential for long-term change, either increases or decline towards extinction, although the risks for common species are generally thought to be quite low. The development of the theory and practice of Population Viability Analysis allows an understanding of how such uncertainty in the key demographic parameters from year to year affects long term population trends, and it can used to develop predictions over predetermined time periods. It must always be borne in mind that PVA is essentially an exercise in estimating probabilities, and that figures produced by such methods are probabilities of different population trajectories over time. Because PVA models are simulation models, they can also be used to examine the effect of changing one or more of the demographic parameters on the long-term viability of the population. Another important use relates to the impact of catastrophic events where large numbers (often more than 50%) of the population die over a very short time period. Although the frequency and severity of such events is poorly known in animal populations, such events do occur, especially those arising from severe weather conditions or outbreaks of disease. Outbreaks of disease are known in wild geese, but their contribution to population dynamics is poorly understood. A recent and better-known example is the outbreak of phocine distemper virus which killed a very large percentage of the common seals occurring in the seas around the UK.

Population thresholds

When running the predictive models for each of the goose species/populations note was taken of the population size categories adopted in the African-Eurasian Waterbird Agreement ⁷. These are detailed in Annex 3.2; which shows that the category changes occur at levels of 10,000, 25,000 and 100,000 birds. In line with this, and noting Recommendation 32 of the National Goose Forum report, a range of biologically meaningful quasi-extinction thresholds was adopted for presentation. For Greenland white-fronted goose, Greenland barnacle goose and Svalbard barnacle goose these were 1,000, 5,000 and 10,000; for greylag goose 5,000, 10,000 and 25,000; and for pink-footed goose 10,000, 25,000 and 50,000.

Application of PVA models to the management of wild species

Most PVA models have been applied to species of conservation concern, in an attempt to establish circumstances under which the population could either be enhanced or managed in such a way as to sustain a viable population in the longer term.

PVA models appear to have been used less frequently as part of the information base for setting management goals for populations either at favourable conservation status or for populations that are considered as 'problem' species. However, use of such models is increasing, and there are several such examples for North American geese. All these models have been used to test, theoretically, the effect of changes in management upon these populations, and have not been used to determine 'target' population sizes. Such models are still at an early stage of development and to date there has been little practical or experimental validation of this approach. Hence this procedure, although offering valuable insights into population management, must be viewed with some caution.

Pink-footed goose

Main findings of PVA

• The current population of pink-footed geese, of about 230,000 individuals, is healthy and the long-term likelihood of decline under current conditions is very small. The risk from any catastrophic events is also very low, except in the most extreme conditions modelled.
• If the current conditions and levels of shooting (c.13,000 in Iceland and c.25,000 in the UK) are maintained the predicted median equilibrium pink-footed goose population size is approximately 220,000, and there is just a 2% probability the population will decline below 50,000 within 25 years.
• The quasi-extinction probabilities are most sensitive to changes in adult survival. However even this rate needs to be reduced quite significantly in order to obtain a 25% probability that the population will fall below 50,000. To observe this level of quasi-extinction risk further reductions to the current mean adult survival, juvenile survival or productivity of 8%, 44% or 46% respectively are required.
• The current level of shooting appears to be sustainable. A reduction in the number shot per year of 5,000 reduces the predicted probability of population decline below 50,000 within 25 years from 2% to 0.4%. However, if an additional 5,000 geese are shot per year the likelihood of decline below 50,000 in 25 years increases to 11% and the average population size after 25 years falls to 180,000.

Policy implications for goose conservation and management

• The Icelandic/Greenlandic population of pink-footed geese is currently healthy and the current level of shooting appears to be sustainable. However, the PVA suggests that a comparatively small increase in shooting pressure in the UK and/or Iceland could lead to a long-term decline. As this species is a legitimate quarry species, no management issues related to this arise at present, although adequate monitoring of the shooting bag is needed to maintain robust population analyses.
• For the close season especially during late winter and early spring, licences are already issued, where appropriate, to prevent serious damage to crops. There appears to be no good scientific reason for varying this practice, with the usual consultative approach in areas where populations linked to SPAs are at issue.
• It is imperative that good monitoring of the population size continues and adequate assessment of shooting mortality occurs. At present, the autumn roost counts (in October and November) give an acceptably accurate record of the population size.

Advice

There appear to be no scientific reasons to vary the current regimes for management or shooting of pink-footed geese in Scotland. The development of adequate means of monitoring of hunting bags is proposed.

Greenland white-fronted goose

Main findings of PVA

• Following a period of steady growth through to the mid 1990s the overall population had stabilised but is now showing signs of a more recent decline to a current Scottish level of 17,500. These changes appear to have been driven by a reduction in the proportion of breeding birds, rather than any changes in the mean brood size or adult survival rate.
• The baseline model predicts an equilibrium Scottish population size of around 20,000, with a low risk of decline below 10,000 within 25 years, assuming the conditions experienced over the last 20 years are maintained.
• The population appears to be currently regulated by density dependent processes and future projections are particularly sensitive to any change in adult survival.
• Expansion of the Greenland breeding population of Canada geese, and subsequent competition for territories with white-fronts may severely reduce the latter's overall productivity, leading to a high risk of significant population decline.

Policy implications for goose conservation and management

• The conservation status of the Greenland white-fronted goose population has improved markedly over the past few decades but recent evidence of a substantial reversal in the population trend raises some concerns. Given the potential vulnerability of this population to quite small changes in additional mortality we suggest that the population should retain its current protected status.
• Greenland white-fronted geese, except for the issue of historic habitat losses, appear to be currently free from substantive threat on their wintering grounds in Scotland. The key constraints appear to operate on their breeding grounds in west Greenland and while staging in Iceland.
• Research should be encouraged in Greenland into the reasons why the proportion of adults breeding has declined and the role of Canada geese in this.

Advice

Given the vulnerability of the Greenland white-fronted goose population to additional mortality there should be a presumption against a change in the protected status of the subspecies, and against the issue of licences for shooting to prevent serious agricultural damage. There appear to be no scientific reasons to vary the current regimes for management of Greenland white-fronted geese in Scotland.

Tackling the key current constraints to maintaining the favourable conservation status of Greenland white-fronted geese (competition with Canada geese in Greenland and hunting mortality in Iceland) requires international collaboration; this is to be encouraged.

Icelandic greylag goose

Main findings of PVA

• The autumn counts have described a sustained period of population growth in the GB wintering population peaking at around 100,000 birds in the early 1990s, followed by a decline to about 73,000 in 2002. There is currently a great deal of uncertainty in the PVA estimates, with suggestions that these counts underestimate the full size of the population, that there are problems with estimating the proportions of juvenile birds, and that it is getting increasingly difficult to distinguish between Icelandic greylags and the resident native and reintroduced greylag populations.
• If current conditions are maintained the best-fit model predicts that the population will decline by approximately 3.5% per year, with a 58% probability that the population will fall below 25,000 within 25 years. There is currently no compelling evidence for the presence of density dependent regulation of population change.
• While the quasi-extinction probability is most sensitive to adult survival, reduction of either juvenile survival or productivity also leads to an elevated risk of significant population decline.
• The underlying demographic parameters indicate that this population is currently under hunting stress and that the current level of hunting in both Iceland (c.35,000) and Scotland (15,000 - 25,000) combined is unsustainable over the medium term.

Policy implications for goose conservation and management

• The fortunes of Icelandic greylags have changed considerably over the last 10-15 years with a pronounced reversal of the previous upward trend. Substantial changes in winter distribution have also occurred. Evidence now points to current shooting levels being unsustainable with a high probability of substantive further decline in numbers if these pressures do not change.
• It is imperative that continued and improved monitoring of the population size and of shooting mortality occurs, and that monitoring problems identified in the PVA and other studies are addressed.
• For the close season, especially during late winter and early spring, licences are currently issued in some areas to prevent serious damage to crops. We suggest that this is monitored and assessed very carefully due to the adverse ecological impact of spring shooting. Measures are also needed to encourage a voluntary reduction in hunting take during the open season. We note that the PVA study suggests that a relatively small reduction in shooting pressure may be sufficient to arrest the current decline in population size.

Advice

Measures should be taken in Scotland to adapt the shooting take of Icelandic greylag geese to sustainable levels. These measures should address open season bags and closed season licences. We can take action in Scotland, but a degree of international collaboration is needed with development of adequate tools for the regular assessment of population size, productivity and hunting bags.

Greenland barnacle goose

Main findings of PVA

• The current size of the Greenland barnacle goose population (56,400 globally with 47,300 in Scotland) appears reasonably secure in the long term. Under current conditions the population is predicted to continue to grow, though rates of growth may vary between different wintering locations.
• There is some evidence that density dependent mechanisms may be operating in the Islay sub-population. If so, then numbers on Islay are predicted to remain near the 2003 level of approximately 35,000.
• The greater population growth seen on Islay compared to the other sub-populations appears to have been a result of higher productivity amongst Islay birds, rather than differential rates of movement between wintering locations.
• Greenland barnacle geese are currently legal quarry in Iceland and are shot under licence in Scotland. If the numbers shot each year remain at current levels the predicted risk of population decline below 10,000 in 25 years is less than 0.3%. If density dependence is operating the additional removal in Scotland of as few as 500 individuals annually may be sufficient to reduce the median equilibrium population on Islay to less than 30,000, increasing the risk of decline below 10,000 within 25 years to 2.5%.
• The population does not appear to be particularly sensitive to catastrophic mortality events, requiring frequent, moderate to large losses before the risk of population decline below 10,000 becomes significant.

Policy implications for goose conservation and management

• The Greenland population of barnacle geese is healthy and currently increasing overall in Scotland. However, population trends vary in different parts of the Scottish wintering range.
• Licensed shooting to prevent serious damage to crops is currently undertaken on Islay to reinforce scaring as an aid to overall management. At the current population level the PVA analyses suggest that if the current level of shooting is maintained there is not a significant risk of population decline. If additional shooting of 500 birds were to occur, the PVA predicted that this would lead to population decline, with a greater than 70% chance that the population would fall below 25,000 in the next 25 years. The PVA also suggests that if density dependence is operating as modelled, the Islay population is predicted to remain near its current size.
• Almost all the detailed data on population demographies for this goose population derives from Islay and PVA modelling was restricted to this Islay sub-population. This makes it more difficult and risky to predict changes for the whole population and inappropriate to do so for the smaller sub-populations in other locations. Improved demographic information for birds wintering on other sites would greatly improve our understanding of their relative contributions to the population.

Advice

Current levels of licensed shooting of Greenland barnacle geese on Islay (c.500 birds per annum) do not appear to be having a negative effect on population size. There appear to be no scientific reasons for changing the current management regimes across Scotland.

Svalbard barnacle goose

Main findings of PVA

• The current level of 27,000 barnacle geese wintering on the Solway is relatively healthy, especially compared to the situation some 50 years ago. There is currently no evidence to suggest the population has reached the carrying capacity of either the summer or winter range. However, there is evidence that reproductive output has declined with increasing population size.
• If breeding is being regulated by population density, then further increases in population size may be relatively modest compared to those seen over the previous 15-20 years. However, this assumes the maintenance of the current breeding range in Svalbard. If new breeding colonies continue to be established then the population may continue to grow.
• The most sensitive demographic rate is adult survival. Under conditions of density dependence, additional loss of as few as 350 individuals annually produces a median equilibrium population at its current size of 27,000. The likelihood of long-term population decline increases markedly if additional annual losses exceed 1000 or more.
• The aggregation of this population into one breeding area and one principal wintering area makes this population more vulnerable to chance catastrophic events, such as adverse conditions on the breeding grounds, disease or adverse conditions during migration.

Policy implications for goose conservation and management

• The Svalbard population of barnacle geese has continued to rise and seems likely to continue to do so, albeit at reduced rates, as productivity has declined with increasing population size. Future trends look more likely to be dependent upon developments or changes on the breeding grounds.
• The PVA suggests that on average, an increased mortality of 350 birds per annum would produce a stable population at its current size of 27,000. However, a different element of the analysis shows that the confidence limits of the modelling are such that there is a greater than 70% chance that any mortality above current natural levels would result in a decline to below 25,000 birds over the next 25 years. A decline below 25,000 would move the population back into a higher threat category under the African-Eurasian Waterbird Agreement classification.
• The outcomes of the currently ongoing FRAGILE project may inform future management priorities for this population.

Advice

The new PVA modelling has shown the vulnerability of the Svalbard barnacle goose population to additional mortality. Due to this there should be a presumption against a change in the protected status of the population. There is no scientific reason to alter the current management regime for Svalbard barnacle geese in Scotland.

3.2 AEWA classifications and status of Scottish goose populations

African-Eurasian Waterbird Agreement Text

Status of the Populations of Migratory Waterbirds

KEY TO CLASSIFICATION:

Column A

Category 1:

(a) Species which are included in Appendix I to the Convention;

(b) Species which are listed as threatened in the 1994 IUCN Red List of Threatened Animals (Groombridge 1993); or

(c) Populations which number less than around 10,000 individuals.

Category 2: Populations numbering between around 10,000 and around 25,000 individuals.

Category 3: Populations numbering between around 25,000 and around 100,000 individuals and considered to be at risk as a result of:

(a) concentration onto a small number of sites at any stage of their annual cycle;

(b) dependence on a habitat type which is under severe threat;

(c) showing significant long-term decline; or

(d) showing extreme fluctuations in population size or trend.

Column B

Category 1: Populations numbering between around 25,000 and around 100,000 individuals and which do not fulfil the conditions in respect of Column A, as described above.

Category 2: Populations numbering more than around 100,000 individuals and considered to be in need of special attention as a result of:

(a) concentration onto a small number of sites at any stage of their annual cycle;

(b) dependence on a habitat type which is under severe threat;

(c) showing significant long-term decline; or

(d) showing large fluctuations in population size or trend.

Column C

Category 1:

Populations numbering more than around 100,000 individuals which could significantly benefit from international cooperation and which do not fulfil the conditions in respect of either Column A or B, above.

The Scottish goose populations are classified as follows:

3.3 Status and monitoring of goose populations in Scotland, including recommendations for future research, survey and monitoring work

Greg Mudge and Rhys Bullman, SNH, 29 April 2005

INTRODUCTION

This paper summarises the current status and recent population trends for Scottish goose populations and assesses the adequacy of the monitoring provisions currently in place. First, generic UK monitoring schemes which apply to Scottish goose populations are described, followed by provisions for the coverage of individual species or populations which occur in Scotland. Population Viability Analyses ( PVA) have been undertaken for Greenland and Svalbard populations of barnacle goose, Greenland white-fronted goose, Icelandic greylag goose and pink-footed goose, so the treatment of these groups in the current report has been superficial as relevant information is covered in the respective PVA Information Papers.

This paper is pitched at a Scotland-wide level. It does not attempt to address status and monitoring issues at local goose management scheme level.

Annex 3.4 summarises the current population sizes and trends of geese that occur in Scotland.

The paper concludes with a prioritised list of research, survey and monitoring projects which could be implemented over the next five years to improve our state of knowledge for the next review of goose policy.

NATIONAL GOOSE MONITORING SCHEMES

The Wetland Bird Survey ( WeBS)

WeBS is a partnership scheme of the British Trust for Ornithology ( BTO), The Wildfowl and Wetlands Trust ( WWT), The Royal Society for the Protection of Birds ( RSPB) and the Joint Nature Conservation Committee ( JNCC) on behalf of the statutory country agencies. The principal aim of WeBS is to monitor all non-breeding water birds in the UK and to collect count data in order to inform decisions about the conservation of their populations and wetland habitats. The scheme has three main objectives:

• to assess the size of non-breeding waterbird populations in the UK.
• to assess trends in their numbers and distribution.
• to assess the importance of individual sites for waterbirds.

Co-ordination of monitoring of UK goose and swan populations by WWT

Whilst most monitoring of non-breeding waterbirds is undertaken through the Wetland Bird Survey ( WeBS), the monitoring of some goose and swan populations has historically been subject to separate arrangements because of the need for different survey methodologies to collect data from areas that are often remote, as well as the pre-existence of different networks of counters and study groups already undertaking survey activity.

The contract from JNCC on behalf of the statutory country agencies to provide the necessary co-ordination of goose and swan monitoring through schemes such as the National Grey Goose Census and the Greenland White-fronted Goose Study has been awarded to WWT. The outputs from these surveys are provided to WeBS for inclusion in national datasets as well as annual reporting in the WeBS annual publication Wildfowl and Wader Counts.

Monitoring in goose scheme areas

Detailed monitoring of geese is undertaken within each of the Local Goose Management Schemes. The approach adopted within each of the scheme areas is described in the annual scheme reports and reviewed in Mudge, Whitfield & Bullman (2004).

SPECIES ACCOUNTS

Taiga bean goose ( Anser fabalis fabalis)

The main wintering area in Scotland for the bean goose is the Slammannan Plateau in North Lanarkshire. This population, which breeds in Scandinavia and NW Russia, has been counted annually for the last ten winters with up to 200 random visits undertaken per season, usually between late September and early March when both diurnal and roost counts are made. All goose species in the study area are recorded and disturbance factors noted. The Bean Goose Action Group undertakes counts and SNH has a coordinating role. WWT are tasked to coordinate annual productivity assessments and ensure counts are undertaken at key sites. Further monitoring outwith key sites is undertaken by WeBS volunteers.This population has been increasing over the last five years with a peak during the 03-04 winter of 235 birds (5 year mean 99-00 to 03-04 = 206). This current figure represents nearly half of the UK wintering population. The other main wintering area in the UK is in the Yare Valley near Norwich where numbers appear to be decreasing. During the winter of 03-04 there was a peak count of 124 (183 in 2002/03).

Fig. 2. Peak annual count of bean geese wintering on the Slammanan plateau (data from Simpson & MacIver 2004).

Pink-footed goose ( Anser brachyrhynchus)

The Icelandic/Greenlandic population of pink-footed geese has shown a substantial increase in the last 50 years from a population of about 20-30,000 in the early 1950s, stabilising in the 1970s at around 80,000 and then increasing again to a current population of 230,000. Birds breed in the interior of Iceland and in smaller numbers on the east coast of Greenland. In winter most birds occupy low lying agricultural land from the Moray Firth down through Grampian, Tayside, Fife and into the Lothians and Borders. Large numbers also migrate through to Lancashire and Norfolk.

For the last 45 years the population size and distribution of pinkfoot has been monitored by the Icelandic breeding Goose Census ( IGC) co-ordinated by WWT. Total numbers, regional distribution within Scotland, principal concentration areas, and breeding success are summarised annually in a research report (see Hearn 2004a). Two co-ordinated counts are undertaken at key sites annually, one in October and one in November. These counts are timed to coincide with the periods when the geese are arriving from their breeding grounds in Iceland/Greenland. The majority of the counts are taken at roosts during the dawn or dusk period when geese are leaving for or returning from their feeding areas. If regularly counted sites are omitted one year the number of geese for that year is estimated using the mean of the previous five years worth of data.

Reproductive success is also assessed by determining the proportion of young birds in autumn goose flocks.

Greenland white-fronted goose ( Anser albifrons flavirostris)

Greenland white fronted geese breed along the west coast of Greenland, migrate through Iceland, and winter along the west coast of Scotland and in Ireland. Numbers have increased since the early 1980s to a peak of about 34,000 in the late 1990s, but have since declined to about 26,500 in 2002 with some 17,500 birds in Scotland and 9,000 in Ireland. Within Great Britain most birds winter on Islay. Small numbers occur down the west coast from Caithness southwards with substantial flocks on Tiree and Coll, and in Kintyre and Galloway.

Greenland white-fronted geese are monitored at all known wintering sites by an annual census, now in its 23 ^rd year, which is co-ordinated by the Greenland white-fronted goose study (Fox & Francis, 2004). At most sites monthly roost counts are made at dawn or dusk, usually between the months of October and March. International co-ordinated counts are also made during specified autumn and spring census periods. The total number of birds is recorded at each site along with estimates of ages, number of juveniles and brood sizes. WWT are tasked with collating the annual assessment of productivity from the main wintering area of Islay and count data from key sites for submission to the annual WeBS report.

Icelandic population of greylag goose ( Anser anser)

Icelandic greylag geese for many years increased at a similar rate to pink-footed geese, though the trends diverged in the late 1970s when greylag goose numbers remained stable in contrast to pink-footed goose numbers. Although they breed in Iceland, greylag geese tend to concentrate in lower lying coastal areas, and are therefore more prone to shooting and hunting disturbance than pink-footed geese. In the UK birds winter on Orkney, and in low lying agricultural ground around the Moray Firth, Grampian, Tayside and Fife and into the Lothians and Borders. A few birds winter in northern England, although the great majority are in Scotland. The population trend is currently downwards with an estimate in autumn 2002 of 73,000 individuals.

For the last 45 years the population size and distribution of Icelandic greylag has been monitored by the Icelandic breeding Goose Census ( IGC) co-ordinated by WWT. Total numbers, regional distribution within Scotland, principal concentration areas, and breeding success are summarised annually in a research report (see Hearn 2004a). Two co-ordinated counts are undertaken at key sites annually, one in October and one in November. These counts are timed to coincide with the periods when the geese are arriving from their breeding grounds in Iceland. The majority of the counts are taken at roosts during the dawn or dusk period when geese are leaving for or returning from their feeding areas. If regularly counted sites are omitted one year the number of geese for that year is estimated using the mean of the previous five years worth of data.

Reproductive success is also assessed by determining the proportion of young birds in autumn goose flocks.

Native greylag goose ( Anser anser) and reintroduced greylag goose ( Anser anser)

Populations of native and reintroduced greylag geese are small compared to the migratory greylag goose population, nor are they strictly migratory in the sense of overflying national boundaries. Native greylag geese, which formerly bred in wetlands widely across Britain, have been confined to parts of Caithness and Sutherland, Wester Ross and the Inner and Outer Hebrides for at least the past century. Although this population is heavily shot, it is slowly expanding and recovering some of its former range. The reintroduced greylag goose population is often treated separately to the native population, but many birds in the reintroduced population originate from deliberate releases some years ago of birds taken from the native greylag goose population, hence the two populations cannot be genetically distinguished from each other. Significant numbers occur in southwest Scotland.

The majority of Scotland's native greylags occur in the Uists, Coll, Tiree, Orkney and Caithness and Sutherland. Monitoring has been sporadic and patchy with the last full census undertaken in August 1997 (Mitchell et al. 2000). This estimated the total post-breeding population at 10,000+ birds. Current annual monitoring via WeBS does not provide enough data for a full national population estimate but does provide an index based on Hebridean birds. Continued annual counts at some of the key locations indicate a continued increase in numbers with the 2004 population likely to be in the order of 15,000 birds.

WeBS coverage on Harris and Lewis is not currently sufficient to provide an accurate assessment of the population here and a dedicated survey is desirable. Coll was partially monitored in 2004 as part of SNH's Site Condition Monitoring Programme but this work only covered the North East Coll Lochs and Moors SSSI. Tiree is extensively counted by RSPB staff on an annual basis. As a further caveat to the WeBS coverage, NW Scotland birds counted in Orkney and North Highland are included in the Icelandic population totals thus underestimating the total population. Buxton et al. (1995) conducted an aerial survey of all major moulting and breeding habitats of native greylags in Wester Ross and Caithness and Sutherland in July; ground surveys were also undertaken April - mid September. Although birds were widespread, the vast majority of them used Loch Loyal during the moult. Thus it would be possible to obtain a reasonable estimate of the Caithness and Sutherland population by instigating an annual count of this loch, which is currently not counted.

For the last 3-4 years, WWT has co-ordinated an annual count of native greylags in a number of areas, to coincide with the annual Uist census and other Hebridean censuses. New emphasis has been placed on collecting productivity data for several areas in 2005. WWT are likely to coordinate the next national census in 2006.

It is possible to establish whether a given group of greylag geese are from Iceland or NW Scotland by counting birds prior to the arrival of the migratory Icelandic population. This has been done since 2001. Although the validity of this method has yet to be fully tested it can provide useful estimates in some regions, principally the Hebrides (Hearn 2004a).

National surveys of introduced geese carried out in 1989 and in June and July 1991 (Brown & Dick, 1992; Delany, 1993) recorded respectively 2,673 and 2,340 re-introduced greylag geese in Scotland. The majority of these were in Dumfries & Galloway, Lothian, Tayside and Orkney.

Fig. 3. The relative proportions of Icelandic and NW Scottish greylag geese wintering in Scotland. WeBS figures (peak counts) for Icelandic and NW Scotland greylag geese. The NW Scotland data has been derived from counts on Islay, Jura, Colonsay, Mull, Lismore, Coll, Tiree, Skye, Highland Southwest and Lewis, Harris and the Uists.

Canada goose ( Branta canadensis)

The Canada goose is an introduced species. Most of the population breeds and winters in England, though some birds undergo a moult migration to Scotland in a manner similar to the ancestral population in the USA. Scotland is thought to hold about 1,200 birds, and this number may be increasing.

Wintering

The Scottish wintering population of Canada geese (a species introduced to the UK from North America) is monitored via the Wetland Bird Survey ( WeBS) and has remained relatively stable during the last 5-year period for which data are available (96/97 - 00/01) with up to 1342 geese present (five year mean = 1260). In contrast the wintering population in England is considerably larger with a mean of 77941 birds for the same period peaking in 98/99 with 102343 birds. Indices show that numbers of wintering Canada goose at the UK level have increased 5 fold in the last 30 years. Under the JNCCUK goose and swan monitoring contract currently awarded to the Wildfowl and Wetlands Trust ( WWT), they are tasked to collate all incidental records of non-native geese and pass them to the WeBS partnership.

Fig 1: Peak annual monthly counts for Canada geese wintering in Scotland (data from Musgrove et al. 2001)

Breeding

The WeBS estimate of the Canada goose population trend in the UK, probably the most reliable, indicates a 24% increase between 1990 and 2000. Applying this figure to the 1988-91 BTO Breeding Bird Atlas estimate of population size gives a UK figure for 2000 of 29,300 breeding pairs (Marchant pers com)

The proportion of these birds that are in Scotland is poorly known, especially given that the population increase appears to have been uneven between Scotland and the rest of the UK. Frequency index data from the 1988-91 Atlas suggest that just 3% of the UK population was then in Scotland. Applying this figure to the UK estimate gives a figure of 881 pairs of Canada geese in Scotland in 2000; no confidence intervals are available for this figure.

In the national survey of introduced geese carried out in June and July 1991 Delany (1993) recorded 1,088 Canada geese in Scotland. A repeat survey in June and July 2000 recorded 1,244 (Rowell et al., 2004)

Greenland Population of barnacle goose ( Branta leucopsis)

The Greenland population of barnacle geese has increased markedly in the last 30-40 years, and is now probably as high as it ever has been. The current population estimate is 56,400 individuals, which all breed in eastern Greenland. The bulk of the wintering population occurs on Islay. There are smaller numbers at other west-coast island locations, ranging from Orkney in the north, through to the Outer Hebrides, and on Tiree and Coll. About 9,000 birds winter in Ireland.

The remote sites are surveyed by air and there have been 11 such surveys since 1959, conducted at approximately 5 year intervals (Worden et al. 2004). Since the early 1970s the largest single population has been on Islay, which currently holds an estimated 77% of the Scottish population (and 65% of the global population). In addition, since the 1960s an estimate of the proportion of juveniles and the mean brood size have also been made each autumn.

WWT collate the annual assessment of productivity from the main wintering area of Islay and provides this to the WeBS annual report along with the annual land-based population estimates at key sites such as Islay and South Walls. These estimates are provided to JNCC by June each year. The counts and productivity estimates are generally undertaken by SNH staff.

Svalbard population of barnacle goose ( Branta leucopsis)

This population, which breeds entirely on Svalbard, has also increased from a very low level in the 1940s (with perhaps as few as 300 birds) to the current estimate of 27,000 birds. Almost all of the population winters around the Solway Firth, mainly on the Scottish side, principally around Caerlaverock and Mersehead, though increasing numbers are using Calvo, Newton and Skinburness Marshes on the English side. Smaller numbers are found at a number of eastern coast localities, especially early on in the season (such as Loch of Strathbeg and Loch Leven). In the early 1990s the population was thought to be stabilising, but is now increasing again, probably due to expansion into new breeding habitat on Svalbard.

For nearly 50 years WWT has conducted an annual count of the barnacle goose population on the Solway. In addition it estimates annually the proportion of juveniles present and the average brood size. Until the winter of 1998-99, co-ordinated total population counts were made in mid October, with occasional counts also made in other months. The October counts were used to estimate total population size. In 1999-2000 and 2000-2001, one count was conducted each month from October to April inclusive, and the annual count was derived from these. From winter 2001-02 onwards, more regular (twice-monthly) counting has been undertaken, and the annual population size estimated as the average of the top 10% of these counts (Trinder et al. 2004). Annual indices indicate that for the period 1990-91 to 2000-01 the population more than doubled in size.

Other species

In addition to the above species Scotland supports small numbers of the following:

Brent goose - small numbers regularly occur during passage and in winter.

Snow goose - small numbers recorded in Argyll (Coll and Mull) and elsewhere.

Bar-headed goose - recorded in central Scotland.

Hybrid geese - occasional records.

ADEQUACY OF CURRENT MONITORING EFFORT AND RECOMMENDATIONS FOR RESEARCH, SURVEY AND MONITORING OVER THE NEXT FIVE YEARS

Annex 3.5 reviews the adequacy of current monitoring effort across a range of parameters and identifies those that need to be improved over the next five years. In large part this assessment is designed to provide better datasets to inform the next five-year review, particularly in respect of goose flocks outwith Islay.

Abdominal profiles provide indices of the condition of individual geese. They can inform assessments of the impact of scaring on body condition at departure in spring and can be used to assess whether there are consistent differences in goose body condition at different wintering sites.

Hunting bags reasonably reliable annual estimates of the hunting take of quarry species are needed in order to understand the reasons for population changes and to allow fine tuning of hunting pressure in response to these changes.

Ring re-sightings allow more accurate estimation of survival and to improve understanding of goose movements between wintering sites and while on passage.

Annex 3.6 converts this into a prioritised list for each species and incorporates a number of additional, broader research topics.

Bean goose

Current monitoring effort at the Slamannan Plateau is more than adequate.

Recommendation: No changes are required in current monitoring effort for bean goose.

Pink-footed goose

The full population in Scotland and England is counted twice each year (October and November) and seems to be producing reasonably estimates of population size and the proportion of juveniles. This level of monitoring would appear to be adequate and should be continued. The main shortfall lies with the availability of hunting bag data.

Recommendation: Proposals need to be developed for making an annual assessment of the hunting bag of pink-footed geese across the population as a whole.

Greenland white-fronted goose

Current monitoring of overall numbers and distribution would appear to be adequate and should be continued. The key shortfalls are in the collection of breeding productivity data at a wider range of wintering sites. Further collection and analysis of abdominal profile data on Islay and elsewhere is also seen as important.

Recommendation: Brood size, proportion of juveniles and abdominal profile data should be collected for Greenland white-fronted geese at a wider range of sites.

Icelandic greylag goose

The full population in Scotland and England is counted twice each year (October and November). Unlike the case with pinkfeet, concern has recently been expressed about the accuracy of the results obtained both in terms of absolute numbers and age structure (Frederiksen et al. 2004). In addition to this some native and reintroduced greylags are also included in the October and November censuses. These issues need to be addressed and Hearn (2004b) has recently made a set of proposals. Given the degree of hunting stress detected in this population it is important that a better measure is obtained of changes in hunting pressure.

Native greylag goose

The numbers and range of native greylags are currently undergoing rapid change. Regular counts are conducted in some areas, e.g. Coll & Tiree and the Uists, but many other areas are counted only infrequently. A more regular, Scotland-wide perspective is currently desirable. The last full late summer census was conducted in 1997 and the next is planned for 2008. These censuses need to be carried out more frequently using a robust survey methodology.

Orkney and north Highland birds are included in the Icelandic population totals in WeBS reporting. This can be overcome by regular late summer counts in these areas prior to the arrival of Icelandic birds. As the Loch Loyal post breeding flock is highly representative of the whole Caithness and Sutherland population an annual count of this flock would be desirable.

Reintroduced greylag goose

Current WeBS coverage is incomplete and dedicated national censuses have been infrequent. As numbers increase it would be reasonable to look for a better handle on numbers and distribution, not least to assist understanding of events pertaining to the Icelandic and native greylag populations.

Recommendation: Monitoring of population size and distribution of Icelandic greylag goose needs to be improved and integrated with the assessment of numbers and distribution of native and reintroduced greylags. This will require a degree of international collaboration.

Recommendation: Brood size and proportion of juveniles data should be collected for Icelandic and native greylag geese at a wider range of sites.

Recommendation: Following collection of enhanced demographic data for native greylag goose, including ring resightings, a full PVA should be conducted on this population.

Recommendation: Proposals need to be developed for making an annual assessment of the hunting bags of Icelandic, native and reintroduced greylag geese.

Canada goose

Data for numbers of breeding Canada geese are limited and not sufficient to produce a national population estimate. Currently the Scottish breeding population is inferred from numbers present in the winter and it may be that this is a suitable method for approximating the total. It may, however, be prudent to instigate a dedicated survey in the breeding season with the aim of testing the accuracy and efficacy of the inferred count.

Recommendation: No changes are required in current monitoring effort for Canada goose.

Greenland barnacle goose

The full population in Scotland and Ireland is censused by a mix of aerial and ground counts approximately once every 5 years during the month of March. In the report of the most recent census Worden et al. (2004) recommend that the frequency of these counts is increased to two full censuses every six years. However, approximately 87% of the Scottish population is counted from the ground on an annual basis in scheme areas. The shortfall therefore lies in the frequency of counts at the more remote locations and in the availability of annual and seasonal overviews of the distribution of the full population. Organisation of the full censuses is logistically difficult (coordination with teams of ground counters and weather constraints on flying) and costly and this has to be balanced against the value of the additional information that more frequent censuses would provide. The potential exists to obtain more frequent ground counts at some locations and SMRU seal census work overlaps with some barnacle goose wintering sites.

Recommendation: Retain the current frequency of full aerial censuses of Greenland barnacle geese (once every 5 years) but seek to obtain more ground counts at suitable locations and investigate whether Sea Mammal Research Unit seal censuses could provide information on some goose sites.

Recommendation: Brood size, proportion of juveniles and abdominal profile data should be collected for Greenland barnacle geese at a wider range of sites. More effort should be put into collecting ring sightings at remote sites.

Svalbard barnacle goose

Current monitoring effort is more than adequate. It should be continued albeit count frequency could be reduced should WWT desire.

Recommendation: No changes are required in current monitoring effort for Svalbard barnacle goose.

Other introduced and hybrid geese

While not currently abundant or troublesome in Scotland it would be wise to maintain a basic level of surveillance of snow goose, bar-headed goose and other naturalised and hybrid geese. This is adequately achieved through existing WeBS counts coupled with periodic dedicated surveys by volunteers of naturalised geese.

Recommendation: Maintain surveillance of the numbers and distribution of snow goose, bar-headed goose and other naturalised species and hybrids via existing WeBS counts and periodic (nine-yearly) GB-wide surveys of naturalised geese.

REFERENCES

Brown, A.W. & Dick, G. (1992). Distribution and numbers of feral greylag geese in Scotland. Scottish Birds, 16: 184-191.

Buxton, N.E., Symonds, F. & Bregazzi P. (1995) The numbers and distribution of the Native Greylag Goose ( Anser anser) on the North Scottish Mainland. SNH Commissioned report, NW 592.

Delany, S. N. (1993) Introduced and escaped geese in Britain in the summer 1991. British Birds 86: 591-599

Fox, T. & Francis I. (2004) Report of the 2003/2004 National census of Greenland white-fronted geese in Britain. Greenland white-fronted goose study group.

Frederiksen, M., Hearn, R.D., Mitchell, C., Sigfusson, A., Swann, R.L. & Fox, A.D. (2004) The dynamics of Icelandic goose populations: a reassessment of the evidence. Journal of Applied Ecology, 41: 315-334.

Hearn, R.D. (2004a) The 2002 Icelandic-breeding Goose Census. WWT, Slimbridge.

Hearn, R.D. (2004b). Recommendations for survey design to estimate the abundance of the Iceland Greylag Goose population in the United Kingdom. WWT report to JNCC.

Madsen, J., Cracknell, G. and Fox, A.D. (eds.) 1999. Goose Populations of the Western Palaearctic. A Review of Status and Distribution. Wetlands International No. 48, Wetlands International, Wageningen, The Netherlands, National Environment Research Institute, Ronde, Denmark, 344pp.

Mitchell, C., Patterson, D., Boyer, P., Cunningham, C., McDonald, R., Meek, E., Okill, J.D. & Symonds, F. (2000) The Summer status and distribution of greylag geese in north and west Scotland. Scottish Birds, 21, 69-77.

Mudge, G.P., Whitfield, P. & Bullman, R. (2004). Proposals for goose monitoring and reporting methods to be employed by Local Goose Management Schemes in Scotland. SNH report to NGMRG.

Musgrove, A.J., Pollitt, M.S., Hall, C., Hearn, R.D., Holloway, S.J., Marshall, P.E., Robinson, J.A. &

Cranswick, P.A. (2001) The Wetland Bird Survey 1999-2000 Wildfowl and Wader Counts. BTO/ WWT/ RSPB/ JNCC, Slimbridge.

Rowell, H., Ward, R., Hall, C. & Cranswick, P. (2004). The naturalised goose survey 2000. WWT Research Report.

Simpson, J. & MacIver I. (2004) Population and distribution of bean geese in the Slamannan area. Bean Goose Action Group report to SNH

Trinder, M., Rowcliffe, M., Pettifor, R. & Rees, E. 2005. Information paper: Status and population viability of Greenland white-fronted geese in Scotland. Unpublished report to SNH.

Trinder, M., Rowcliffe, M., Pettifor, R., Rees, E, & Griffin, L. (2005) Information paper: Status and population viability of Svalbard barnacle geese in Scotland. Unpublished report to SNH.

Worden, J., Mitchell, C., Merne, O. & Cranswick, P. (2004). Greenland barnacle geese Branta leucopsis in Britain and Ireland: results of the international census, spring 2003. WWT report, Slimbridge.

3.4 Population sizes and trends for the main wintering and breeding populations of geese occurring in Scotland

Information as of January 2005

^1.Hearn,R. 2004.
^2.Worden, J., Mitchell, C., Merne, O. & Cranswick, P. 2004.
^3.Trinder, M., Rowcliffe, M., Pettifor, R., Rees, E. & Griffin, L. 2005.
^4.Trinder, M., Rowcliffe, M., Pettifor, R. & Rees, E. 2005.
⁵ Mitchell, C., Patterson, D., Boyer, P., Cunningham, P., McDonald, R., Meek, E., Okill, J.D. & Symonds, F. 2000.
⁶ Delany, S. N. (1993)
⁷ Madsen, J., Cracknell, G. and Fox, A.D. (eds.) 1999.
⁸ The 2003 counts estimated a total of 281,000 pinkfeet.
⁹ The 2003 counts estimated a total of 81,000 greylags.

3.5 Monitoring of aspects of Scottish goose populations: the adequacy of current monitoring and need for improvements over the next five years

3.6 Goose research, survey and monitoring needs: draft prioritised project list

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