Abstracts of presentations

to the

Wetlands International

Seaduck Specialist Group Meeting

Workshop on Baltic/North Sea common eider populations

and

Progress workshop on Steller’s eider

17-21April 2002

at Roosta Holiday Village, Estonia

 

Convened by the Wetlands International Seaduck Specialist Group

and National Environmental Research Institute, Denmark

 

 

 

Dear All,

 

We thought it would be helpful for all participants at the Eider Workshop if we could compile a booklet of abstracts prior to the meeting, so everyone has some idea of what is likely to be discussed in the presentations. In addition, it provides a useful reminder after the meeting about what was said. We are extremely grateful to all the contributors for taking the time and making the effort to prepare abstracts in this way. It has been an enormous help in planning the meeting and organising the structure of the workshop. We very much hope it is useful to all the participants, and would wish to point out that any errors or misinterpretations of the sub-editing process are the fault of the undersigned, and not that of the authors!

Amongst the abstracts here is a contribution from Ævar Petersen, from the Icelandic Institute for Natural History, who will not be able to participate. Nevertheless, he was kind enough to send a very interesting document that represents a national progress report (the third such report) from Iceland on the national implementation there of the Eider Conservation Strategy. This is a CAFF initiative, which perhaps we could usefully consider with reference to the Baltic/North Sea common eider population that is the theme for the major part of the workshop. We shall bring some supporting material for discussion.

We wish everyone a very enjoyable meeting and our hearty thanks again to our Estonian hosts and the local organising committee for making this dream become a reality!

 

 

Tony Fox

NERI, Denmark

 

A common eider population in the archipelago of Stockholm and its response to an invasion by American mink

Åke Andersson

Swedish Association for Hunting and Wildlife Management, Research Unit. Present address: Ringgatan 39 C, S-756 51 Uppsala, Sweden. e-mail: ake.andersson@sjf.slu.se

The invasion of the non-native American mink (Mustela vison) into the Stockholm archipelago study area started in the early 1970s. A complete census of eider (Somateria mollissima) nests was carried out in 1970 and was followed by ecological studies of the species in 1971-1975. Data collected during these years are used to document the pre-mink situation.

In subsequent years, mink gradually colonised more and more islands, until the outermost were reached for the first time in 1993. Since then, the species occurs throughout the area. Counts of eider nests were carried out on a sample of islands at irregular intervals during 1979-1996. In 1996, an intensified mink persecution programme started in part of the study area and given an experimental design. The responses of prey species have been recorded in experimental and control areas.

Eider females have dramatically changed their nesting habits since the arrival of the mink. They have abandoned bushy and wooded islands and moved to gull colonies or joined solitary nesting gulls on small islets. Overall, the eider population has decreased significantly. In recent years, the numbers of other predators have increased and must be considered in the interpretation of the present situation.

 

 

Managing nesting habitat for common eider in the St. Lawrence River estuary

Bédard, J.1, Giroux, J.-F.1,2, Huot, J.1,3, Nadeau, A.1 & Filion, B.4

1 Société Duvetnor Ltée, P.O. Box 305, 200 Hayward, Rivière-du-Loup, Québec, G5R 3Y9, Canada.

2 Université du Québec à Montréal, Département des sciences biologiques, P.O. Box 8888, Station Centre-ville, Montréal, Québec, H3C 3P8, Canada. e-mail: giroux@tourduvalat.org

3 Université Laval, Département de biologie, Ste-Foy, Québec G1K 7P4, Canada

4 Ducks Unlimited Canada, 710 rue Bouvier, Suite 260, Québec, Québec G2J 1A7, Canada.

Approximately 28,000 pairs of common eiders (Somateria mollissima dresseri) breed on several islands in the St. Lawrence River estuary. In May-June 1985, an outbreak of avian cholera (Pasteurella multocida) killed about 40% of the estimated 5,000 females that nested on Île Blanche. This island covers 3.9 ha and the birds were nesting underneath a dense cover of high shrubs (Sambucus pubens) and fir snags (Abies balsamea). In the following weeks, Ducks Unlimited Canada in collaboration with La Société Duvetnor and the Canadian Wildlife Service cut and burned all the dead trees and shrubs, scarified the surface with heavy machinery, drained several fresh-water pools (believed to act as reservoirs for the bacteria) and seeded a mixture of grasses (Phalaris arundinacea, Bromus inermis, Agrostis alba) to overcome the temporary loss of nesting cover. Finally, 1,400 3-yr old spruce (Picea mariana) seedlings were transplanted and 450 plywood nest-shelters were installed. The number of nesting eiders declined steadily to a low of 1,300 pairs in 1995. Since then, numbers have gradually increased and reached 3,900 in 2001. No other major cholera outbreaks have been reported on Île Blanche, although 50 and 125 female eiders were found dead in 1988 and 1991, respectively. Due to the lack of nesting cover, the use of the shelters reached 90% in the first two years, decreased somewhat in the following two to three years, and then rose again, perhaps as young females born under them were recruited into the breeding population. Shelter use decreased again with the overall decline of the population and then gradually increased to 92 % in 2001. Large shelters (108 x 72 x 17 cm) with a central divider received greater use than narrow ones without dividers (108 x 54 x 17 cm) although narrow shelters with a divider were more cost-effective. Nests under shelters were initiated earlier, had a larger clutch size (4.5 vs. 3.5 eggs) and suffered less predation by gulls but were more likely to be abandoned than nests under neighbouring grass cover. To further assess the usefulness of nest-shelters, a total of 350 have been installed on 3 other islands. On Île-aux-Alouettes, a low gravel bar with sparse herbaceous cover, more than 95 % of the 200 shelters have been used by nesting females every year between 1991 and 2001 whereas on medium sized islands with grass (IÎe-aux-Pommes, n=100) and woody (Gros Pèlerin, n=50) cover, they have been largely ignored. The technique seems appropriate on small islands or reefs (< 3 ha) with a high density of nesting pairs (>500 nest/ha) and a paucity of robust (wooded or herbaceous) standing vegetation that can serve as natural cover. It can also be used whenever the latter is temporarily deficient as was the case on île Blanche in the year following management.

 

 

The common eider Somateria mollissima in the southern end of its range: the wax and wane of a population currently stressed by chronic food shortage?

Kees (C.J.) Camphuysen

CSR Consultancy, Ankerstraat 20, 1794 BJ Oosterend, Texel, The Netherlands. e-mail: camphuys@nioz.nl

Common eiders Somateria mollissima established a small breeding colony in The Netherlands in 1906. Until the early 1930s, no more than a few tens of pairs bred in the Wadden Sea area, but the population increased exponentially between the early 1930s and the late 1950s (to c.5500 pairs). Common eiders have probably always been winter visitors in The Netherlands, although wintering numbers in the first half of the 20th century were probably much smaller than in recent years. The first serious attempts to assess wintering numbers in the late 1950s and early 1960s suggested 10,000-40,000 individuals. The breeding population of common eiders crashed in the 1960s, due to poisoning, when nesting adult females in the westernmost colonies were hardest hit. Only about one thousand pairs remained in 1968 when effective countermeasures were taken to reduce the discharges of pesticides in river Rhine. Tens of thousands of common eiders were killed in an oil incident in 1969. The breeding population increased again and levelled off at c.9000 nests in the 1990s. Mid-winter censuses in the 1970s and 1980s indicated a wintering population of 100,000-170,000 birds, most of which originating from Baltic breeding colonies.

The Wadden Sea has always been the prime area for common eiders breeding and wintering in The Netherlands. Very small numbers ventured to North Sea coastal waters or dispersed along the mainland coast further south. A small wintering flock occurred in the Delta area in most years. In 1975/76, an unprecedented exodus towards the mainland coast occurred, involving several thousands, mainly immature common eiders, in a winter when several mollusc-feeding species in the Wadden Sea experienced food shortages. Between 1968 and 1977, a period of rapid colony growth in The Netherlands, chick-production averaged 0.03 pair-1 (range 0.00-0.12 pair-1). Between 1978 and 1988, chick production averaged 0.32 pair-1 (0.07-0.85 pair-1). In the early 1990s, not a single chick survived. Monitoring of common eider breeding success was discontinued in the mid-1990s.

In 1991 and 1992, common eiders experienced very high mortality for a period of nearly two years probably involving tens of thousands of birds. At the same time, the wintering distribution changed markedly and the North Sea gained importance as a wintering area. In winter 1990/91, prior to these events, all wild blue mussel Mytilus edulis banks had been removed from the Dutch Wadden Sea and common cockles Cardium edule became seriously overfished. Common eiders exploited Spisula subtruncata in the North Sea as an alternative source of food. Between 1991 and 1999, a variable proportion of the wintering common eiders formed dense wintering flocks in the North Sea, sometimes even along the mainland coast and the wintering population in the Delta area also increased markedly. Winter mortality was generally higher than in the 1980s, but not exceptional. Mass mortality occurred in the winter of 1999/2000, and the main symptoms were starvation and Acanthocephalan parasite infections. Large numbers of experienced females (ringed in the 1970s) were found dead near the colony. Large numbers died in winter 2000/2001, but mainly involving local breeders. Very large numbers died in 2001/2002, another year in which the North Sea was utilised on a massive scale, but apart from 'local' adults, immatures wintering at sea also died in numbers. The available data suggest that at present, common eiders fail to find sufficient food in The Wadden Sea in most winters. Refuge areas such as the Spisula banks offshore are not always available, in some years have been occasionally overfished, bringing the eiders into direct competition with common scoters Melanitta nigra. Local breeders seem to suffer most and the observations suggest that these birds are not very flexible in their choice of foraging areas in winter.

 

 

The common eider (Somateria mollissima) in Denmark – population trends and dispersal

Mark Desholm & Peter Lyngs

Department of Coastal Zone Ecology, National Environmental Research Institute, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark. e-mail: mde@dmu.dk

 

The talk will give a brief overview of the population trends and dispersal pattern of eiders in Denmark. Denmark has carried out aerial surveys of eiders in Danish waters in mid-winter in the periods: 1969-1973, 1987-1992 and again in 2000. The results indicate an increase of 50-60% between the first two periods and a decrease of about 50% between the last two periods. The Danish breeding population of eiders has been monitored more or less intensively over the last 75 years, and has shown a continuous increase in breeding numbers from c.2000 pairs in 1935 to c.25,000 pairs in 1990. During the last ten years, the population has levelled off at c.24.000 pairs in the last census in 2000/2001. Up to 1990, the population increase could be ascribed to increases at the three largest colonies, whereas the last ten years of stabilisation in numbers is the result of a decline at the large colonies and the establishment of many new and smaller colonies. The dispersal of breeding eiders ringed in Denmark shows three categories of migration strategies: resident, partial migrant and migrant birds. However, all Danish breeding eiders winter in and around Danish waters, with the eastern colonies showing the longest distances between breeding and wintering sites.

 

 

Wintering eider ducks: a description of recent events in Dutch coastal waters and first results of a modelling exercise

B.J. Ens, A.G. Brinkman & R.K.H. Kats

Alterra, P.O. Box 167. NL-1790 AD Den Burg (Texel), The Netherlands. email: b.j.ens@alterra.wag-ur.nl

The talk consists of two parts: (1) A description of the most recent events with regard to the numbers, the distribution and mortality of eider ducks wintering in Dutch coastal waters, (2) a description of a model of the energetics, the prey choice and the distribution of eider ducks wintering in coastal waters.

Until the winter of 1999/2000 the Western part of the Dutch Wadden Sea consistently harboured the largest share of common eiders. Between 1970 and 2000 numbers in the western part of the Dutch Wadden Sea fluctuated between 60.000 and 130.000. Independently, the number of common eiders in the eastern part of the Dutch Wadden Sea fluctuated between a few thousand and 20.000, with one exceptional year (1973) when 60.000 birds were counted. The primary difference between the eastern and the western part of the Dutch Wadden Sea are the large stocks of wild and cultured sublittoral mussels, which are confined to the Western part of the Dutch Wadden Sea. In 2000 the numbers in the Western part of the Wadden Sea dramatically declined to 35.000 birds and similar numbers have been counted in 2001 and 2002. Before 1991 insignificant numbers of common eiders were reported from the North Sea Coastal Zone. Since that time the numbers have fluctuated between 20.000 and 90.000, averaging 40.000 birds. There is a clear negative correlation between the number of common eiders counted in the North Sea Coastal Zone and counted in the Wadden Sea. The changes in distribution since 1970 coincide with peaks in mortality as gauged from the number of dead common eiders collected on the beach. A first mortality peak occurred in the winter of 1990/1991 when a substantial number of ducks shifted to the North Sea Coastal Zone. A second and even higher mortality occurred in the winter of 1999/2000 when the drastic reduction in the number of common eiders wintering in the Western part of the Wadden Sea occurred. Mortality was also high in 2000/2001 and very high again in 2001/2002. Dissection of dead eiders collected in these last two winters indicated starvation as the most probable cause of death, as in the winter of 1999/2000. The peaks in mortality correlate with low landings of consumption mussels from the Wadden Sea. Since low landings indicate a scarcity of sublittoral mussels, it is concluded that scarcity of sublittoral mussels is the most likely explanation for the recent decline in the number of common eiders wintering in the Western part of the Wadden Sea.

On the basis of published information on the energetics of prey choice of eider ducks and related species of ducks a model is currently developed which seeks to explain the prey choice and the distribution of eider ducks wintering in coastal waters. The first stage of the modelling process consists of removing inconsistencies between parameter estimates from different studies. According to the current version of the model, feeding on mussels on long lines in Sweden is highly profitable and this fits with the observation of substantial numbers of eider ducks in the study area. The model can also explain why so few eider ducks winter in the Limfjord in Denmark, despite the presence of large stocks of sublittoral mussels. For a given length the mussels have very thick shells and very little flesh content. Furthermore, the eider ducks have to dive several meters. The model cannot explain why eider ducks are absent from the mussel cultures in La Rochelle, where flesh content of the mussels is good. Three possible explanations exist: (1) the ducks have not (yet) discovered the area which is outside the normal wintering range of the species, (2) all prospecting eider ducks have been shot by French hunters, (3) high costs of flying make it unprofitable for the ducks to move so far south.

 

 

Population trends of the common eider in Finland during 1986-2001

Martti Hario

Finnish Game and Fisheries Research Institute, Söderskär Game Research Station, P.O. Box 6, FIN-00721 Helsinki. e-mail: martti.hario@rktl.fi

 

The results of the nationwide Archipelago Bird Census indicate a current population decline of the common eider in Finland. According to nest count data from 33 census areas along the entire coast (comprising 1550 islands), the numbers of breeding pairs are declining by an average of 6-18% per year depending on the census area. Current population size is estimated to be 150,000-180,000 pairs for the entire coast.

The mid-1990s marked a clear turning point in the development of the Finnish common eider population. Prior to that, there had been an overall increase of 7-10% per year since the mid-1970s. However, subpopulations in the Gulf of Finland behaved slightly differently to those in the SW Archipelago. The Gulf of Finland population showed a gradual but continuous decline as early as the late 1980s, at a time when the SW population was still increasing. However, this comprised just 20,000 pairs then (as against the 150,000 in the SW), so the former decline had little discernible effect on the population trajectory of the entire coast. By 1997, however, populations in the west, too, had started to decline, and the current rate of decrease in the SW core populations now range between 8 and 16% per annum (1997-2001 means of individual census sites). The southern Bothnian Bay population seems to be declining as well, although the confidence limits of estimates generated by the TRIM analysis are wide. No unambiguous trend can be determined from the sparse data of the northern Bothian Bay where the species' range abruptly ends.

Only anecdotal evidence exists from the western census areas relating to fledgling production. This suggests falling rates of reproduction have been caused by high duckling mortality in recent years. More concrete evidence is available from the Gulf of Finland, where a collapse of duckling survival since 1986 resulted in a drastic decline in recruitment rates and consequent population decline. Recently, 1997 and 1998 were better-than-average years with good production of fledglings, and consequently, the population decline appears to have levelled off, although less than was expected. The Söderskär population in the Gulf of Finland has been declining by 5% per annum during 1988-2001. During that time, high duckling mortality appears the main population regulating factor as the net reproductive rate seems to be negatively correlated with the spring population size.


The recent status of the common eider (Somateria mollissima) in the Shetland

Islands: an isolated, declining population.

Martin Heubeck

University of Aberdeen, c/o Sumburgh Head Lighthouse, Virkie, Shetland ZE3 9JN, Scotland, UK. e-mail: martinheubeck@btinternet.com

 

The Shetland population of common eiders is considered resident, with no evidence of regular emigration or immigration. Shetland birds are significantly smaller than those found in north-east Scotland and have been considered closer to the race faeroensis than the nominate mollissima. They make seasonal movements within the archipelago, and concentrate at traditional moulting sites during summer. Because flocks are more dispersed in winter, when daylight hours are limited and weather conditions often poor, population estimates have been based on late summer surveys of all known moulting areas, counting birds from land, boat, or from aerial photographs. The first estimate was of c.17,000 birds in 1977, although some areas since known to have been used were not surveyed. Coverage improved during 1980-1984 and the population was estimated at 11,900 birds in 1984, which included an estimate of 600 birds at three sites not surveyed and scattered females and juveniles away from moulting areas. The population then fell to 8,300 birds by 1990, 6,900 by 1993 and 5,700 by 2001, a decline of 66% since 1977. This decline in the moulting population has been reflected in areas surveyed regularly during winter since the mid-1970s. The initial decrease can be explained by a serious oiling incident in the winter of 1978/79, and heavy mortality the following winter that affected the then largest flock in Shetland; the cause of this latter mortality was never determined but disease or parasitic infection was the most likely reason. The 52% decline since 1984 is less easy to explain. eiders were killed in a number of oiling incidents during the 1990s, including the January 1993 Braer oil spill, but it is unlikely the total mortality exceeded 500 birds, and the main period of decline since 1984 (1984-1991) preceded most of these incidents. Many Shetlanders believe that predation of eider ducklings (and possibly also incubating females) has increased in recent years, but there is little quantitative evidence to support this. Oil pollution remains a potential threat to eiders in Shetland, but the recent expansion of mussel cultivation poses another threat. In spring 2000 at least 25% of Shetland’s eiders were seen feeding at mussel farms. The main method of deterrence to date has been chasing flocks by boat, but a licence to shoot at eiders was issued to one company in late 2001, although subsequently revoked.

 

 

The past and present status of breeding common eiders on islands of Matsalu NR

Eve Mägi & Kaarel Kaisel

Matsalu Looduskaitsela, 90305 Penijõe, Läänemaa, ESTONIA

After the relatively cold period of the 17th and 18th centuries, common eider became abundant in the early 19th century along the Estonian coast and offshore islands. Climate warming reduced eider numbers (Kumari, 1958), so by the middle of 20th century, only a few pairs of eiders were breeding on Moonsund islets (Kumari, 1954).

Numbers of birds breeding on the islands and islets of Matsalu NR have been counted since 1958. At that time, 79 pairs nested on 14 islets, since when very few new breeding areas have been occupied. Most of breeding islets are small – less than 5 ha. There are only 3 islands over 10 ha occupied by eiders.

Eiders nest abundantly on small marine islands (generally stony and relatively far from the mainland) and 96.4% of all eiders nest on just 8 islands. On low "hay-islands" (9 islands) nest densities are sparse, but on favoured islands, breeding densities may reach 300-400 pairs/ha, and up to 700 pairs have nested on Tondirahu islet (which offers excellent concealment conditions). Today, Cormorants now occupy Tondirahu and therefore eiders have disappeared.

During 1958-1997, numbers increased more or less constantly until 1993. After that, numbers started to decline. All islands were counted in 1997, in 1998 3 less important islands were not counted. Further decreases have been estimated by census of other islands, which suggest decreases have been the same on main eider islands as on the less favoured hay-islands.

Average number of eiders on Moonsund islands

Years

1958-62

1963-67

1968-72

1973-77

1978-82

1983-87

1988-90

1991-93

1994-96

1997-98

Eiders

93.8

164.8

335.6

705.6

1339.2

2358

2641.0

4140.0

2967.7

2243.0

On the main islands, the total number of eiders increased by a factor of 64 from 1958 to 1993 compared to 3,6 on hay islands (overall average 44,8 in the population as a whole). The decreases during 1993 to 1998 were accordingly 1,9, 1,6 and 1,8.

Existence of a rich food supply is an important precondition for supporting increasing breeding populations of birds. The biomass of the bottom fauna increased more than 7 fold in the western part of Matsalu Bay due to increased eutrophication during the period 1962-1975. Increases in mussel and snail populations (i.e. major food items for eiders) were largely responsible for this increase (Järvekülg, 1985). In addition to the change in food supply, the availability of suitable islands and islets for nesting in the area supported the increase.

The decreases seen in most recent years probably stem from several potential causes. Foxes Vulpes vulpes have been present on favoured breeding islands almost constantly during the last 10 years. High breeding densities could have increased density-dependent processes, including mortality. Recent more heavy storms have destroying nests close to the waterline. Large gulls (Herring Larus argentatus and Great Black Backed Gull Larus marinus) predate 60 -70 % of nests. As a result, only 15 to 40% of eiders nest successfully (depending on breeding island) at the site.

 

 

Development in the hunting bag of common eiders Somateria mollissima in Denmark

Thomas Kjær Christensen, Tommy Asferg & Ib Clausager

Department of Coastal Zone Ecology, National Environmental Research Institute, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark. e-mail: tk@dmu.dk

Patterns and changes in the number of eiders bagged by hunters in Denmark was analysed using data from the official Danish bag record (1958-1999), and data from the Danish wing survey (1982-1999). The number of bagged eiders has increased from c.100,000 in 1958 to a stable level of c.140,000 during the 1970s and 1980s. Since the early 1990s, numbers have annually decreased by c.6% to c.80,000 in the late 1990s, a decrease comparable with the estimated annual decrease of c.7% in the wintering population. In order to assess the factors influencing the bag size, we included the number of hunters that reported to have shot eiders, the number of days with bagged eiders and the ratio of juveniles/adult female (monthly values) in a stepwise multiple regression model covering the hunting seasons 1983/83-1999/2000. The analysis showed that the number of hunters, number of hunting days and the juvenile ratio in October significantly influenced total bag size, explaining 78.2%, 5.0% and 8.1% of the variation respectively. Since reductions in hunter numbers was not related to decreases in individual hunting success (eiders/hunter), there was no indication that the decrease in total bag size was related to a decreasing number of eiders available to hunters, and thus that the change in bag size reflects population trends. It was assessed that the decrease in eider hunters was related to administrative restrictions affecting waterfowl hunting in general. The low, but significant, influence of the juvenile ratio in October on total bag size suggests that reproductive success in Danish breeding colonies are responsible for annual variation in bag size, although annual bag size is also affected by the number of days available to offshore sea duck hunting.

 

 

 

 

 

Profilicollis botulus (Acanthocephala) abundance in the common eider Somateria mollissima in Denmark

Thomas Kjær Christensen1, Jens Peter Hounisen1 & Tomas Jensen2

1 Department of Coastal Zone Ecology, National Environmental Research Institute, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark. e-mail: tk@dmu.dk

2 Vadehavscentret, Okholmvej 5, DK-6760 Ribe

The occurrence of the intestinal parasite Profilicollis sp. was examined in 122 eiders collected in the Danish Kattegat region (N = 77) and in the Danish Wadden Sea (N = 45) during the winters 2000/2001 and 2001/2002. Hunters retrieved all examined individuals. Except for one juvenile male, all birds appeared healthy. Profilicollis sp. was found in the intestine of 86.4% of the birds from Kattegat and in 85.4% of the birds from the Wadden Sea. In heavily infested birds, the presence of parasites could be seen as multiple small knobs on the outside of the intestine wall, and most parasites were located in the third (59.0%) and fourth (30.7%) quarter of the intestine. There was no difference in parasite loads between areas in different age and sex classes. A difference in parasite loads was found only in adult males, having significantly lower numbers of parasites than adult females and juveniles. The frequency of occurrence of the shore crab Carcinus maenas, the intermediate host of Profilicollis botulus, in the diet was higher in juveniles (25.9%) than in adults (10.4%). Plots of residual body mass (deviation from expected mass) and parasite loads showed no indication that parasite infection had a negative effect on body condition. Likewise, there were no obvious correlations between liver mass, gizzard mass or intestine mass and parasite infection amongst either adults or juveniles. It is assessed that the low parasite infection (low intake of shore crabs) in adult males compared to adult females most probably is related to differences in foraging habitat during the breeding season. Differences in parasite infection between juvenile males and juvenile females are probably more related to differences in prey size, as structurally larger males may take larger crabs that have the highest occurrence of parasite cystacanths.

 

 

A new outbreak of avian Pasteurellosis among breeding common eiders Somateria mollissima in Denmark

Thomas Kjær Christensen

Department of Coastal Zone Ecology, National Environmental Research Institute, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark. e-mail: tk@dmu.dk

The second documented epizootic of pasteurellosis among common eiders in Scandinavia occurred at several Danish breeding colonies in 2001. In three fully searched colonies, the epizootic caused the death of a total of 1,921 females, corresponding to c.30% of the females present within affected colonies. Pasteurellosis or avian cholera, caused by the bacteria Pasteurella multocida, was first documented in Denmark during spring and summer 1996. In the area of southwest Kattegat the outbreak in 2001 occurred at the same colonies as during the 1996 outbreak. However, in 2001, pasteurellosis was also found in one area, Isefjord, that was not affected in 1996. As in 1996, a substantial part of the dead female eider found within the colonies in 2001 were laying within or close to small stagnant freshwater pools on the breeding islets, suggesting that these pools were facilitating spreading the disease. However, P. multocida could not be isolated from samples taken from these water pools. The mass death recorded in both 1996 and 2001 corresponded to a reduction of approximately 10-12% and 8-10% of the total Danish female population respectively. Even though the occurrence of pasteurellosis has had and, in the future, will have a substantial impact on the affected colonies for many years due to the high natal philopatry of female eiders, pasteurellosis is presently not considered a serious thread to the overall Danish breeding population. It is considered that the susceptibility of the breeding population has actually been reduced during recent decades, because large numbers of breeding eiders now occur dispersed between many areas, compared with the previous, highly concentrated occurrence at a few very large colonies during the 1980s. However, future outbreaks of pasteurellosis among eiders may reduce the breeding population strongly, especially if the frequency of occurrence and geographical range is increased.

 

 

Breeding ecology and population development of common eiders in a Danish colony

Thomas Kjær Christensen & Henning Noer

Department of Coastal Zone Ecology, National Environmental Research Institute, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark. e-mail: tk@dmu.dk

In relation to the construction of a fixed link between Denmark and Sweden, investigations of breeding common eiders on the island of Saltholm were conducted during 1993-2000. In all years, data were collected on pre-breeding foraging activity, breeding numbers, clutch size, nesting success, female condition and duckling numbers. Foraging activity of pre-nesting female was high in all years (c.61% of the available daytime) compared to males (c.10.5%), indicating that local resources (bivalves and polychaetes) were extremely important for females about to breed. During the period of investigation, the population declined from c.7,000 in 1993 to c.4,350 in 2000. Substantial non-breeding was only recorded in 1994, where c.20% of the population occurred at the colony but did not breed. A simple Leslie matrix model was used to estimate the population development expected from the observed variation in breeding parameters recorded by the monitoring programme. Based on the recorded variation in breeding numbers, clutch size, nests success and duckling survival, the model estimated a population decline of 3% during 1993-2000, compared to the observed decline of c.38%. Simulations with changes in the expected age at first breeding could not explain the difference between the expected and observed population size. The only parameter that was found to explain the difference was adult survival. To adjust the expected population size to the observed population size, annual survival rates should show changes ranging between 0.71 and 0.87. Compared to the estimated survival rates from other Danish colonies (0.76-1.0), this estimated variation seems not unrealistic, although it implies that the mean adult survival rate of the Saltholm eiders presently is 0.81 and not 0.87 as estimated for a stable population size.

 

 

Status of the common eider Somateria mollissima in the Russian part of the Gulf of Finland and Lake Ladoga.

Kondratyev A.V. & Buzun V.A.

Biological Institute of the S-Petersburg State University. 198904, St. Petersburg, Stary Peterhof, Oraninbaumskoye sch. 2. Russia. e-mail: akondratyev@mail.ru

The common eider Somateria mollissima has just recently been added to the list of breeding species of the Leningrad region. When the islands of the Gulf of Finland started to be opened after military protection of the area during the Soviet period, the species was found on almost all of these islands (Noskov et. al. 1993). At the same time as its discovery as a breeding species in the Gulf of Finland, common eider was also recorded breeding on the Valaam and North-Western archipelagos of Lake Ladoga (Medevedev, Sazonov 1994, Mikhaleva, Birina 1996). The current status of the common eider in the Russian part of the Gulf of Finland and Lake Ladoga is as an uncommon breeder, numbering c.50-150 nests from at least 7 different locations in the Gulf of Finland, and c.30 nests on the islands of Lake Ladoga. Breeding success on the northern Ladoga islands seems to be extremely low (Kondratyev, Lapshin 2001). Wintering females have also been reported near the island of Sommers in the Gulf of Finland (Noskov et. al. 1993).

 

 

Distribution and trends of Norwegian common eider

Svein-Håkon Lorentsen

Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway. e-mail: shl@ninatrd.ninaniku.no

The breeding population of the common eider in Norway was estimated to be 100,000-150,000 breeding pairs in 1994. Breeding numbers have increased in Southern and Western Norway and declined in Central Norway up to the Lofoten area. In Northern Norway the situation is mostly unknown, as is also the present number of breeding pairs. Southern Norway birds migrate to Danish moulting grounds, whereas birds from other parts probably undertake only short moult migrations. Important moulting areas can be found off the coast of Western, Central and Northern Norway, with up to 30,000 birds in certain areas. Common eiders winter along the Norwegian coast, with the highest numbers outside Central and Northern Norway. Most Norwegian birds (except the Skagerrak population) winter locally or perform only short migrations to their wintering grounds. In addition some Svalbard birds winter along the coast of Northern Norway (as well as in Iceland) and (some) birds from the Bothnian Bay migrate to the Trondheimsfjord area to winter. The wintering population probably numbers about 500,000 individuals. In the period from c.1980 to 2000 the wintering populations in Southern and Northern Norway have been relatively stable, but severe population declines.

 

 

 

 

The common eider (Somateria mollissima) population in western Greenland during summer and winter.

Merkel, F.R.1), A.. Mosbech2) and D. Boertmann2)

1) Greenland Institute of Natural Resources, P.O. Box 570, DK-3900 Nuuk, Greenland. e-mail: merkel@natur.gl

2) National Environmental Research Institute, Department of Arctic Environment, P.O. Box 358, Frederiksborgvej 399, DK-4000 Roskilde, Denmark

For more that a century eiders have been extensively utilised in Greenland – eggs and meat for consumption, but also the skin and the down . The tradition for harvesting eiders or eider products combined with recent decades of sociological development (in terms of growth of the human population, better guns and faster boats) have caused growing concern for the status of the breeding population in western Greenland .

Recent surveys in western Greenland confirm the general impression that there has been a large-scale decline in the common eider breeding population. During 1998-2001 ground surveys were conducted systematically along the west coast of Greenland , covering the districts of Ilulissat, Uummannaq, and Upernavik (69° 15’ N - 74° 05’ N). At 15 eider colonies, from which comparable and well-documented surveys were conducted c.40 years earlier, the breeding population amounted to 3,361 nests in 1960-65, but only 662 nests in 1998-2001. This corresponds to an overall decline of 80% or an annual population decline of c.4%. The study revealed considerable year-to-year variation within colonies; however, this cannot explain the overall decline. A similar population trend (73-83% decline) has been documented at breeding areas further south in west Greenland (Kangaatsiaq, 68° 20’ N) over a period of 43 years . Among recent surveyed breeding areas only colonies in northwest Greenland (Qaanaaq) seem to be stable .

Uncertainties still exist regarding some potential eider breeding areas in western Greenland, however, the total breeding population is unlikely to exceed 15,000 breeding pairs at the present time . Based on historical information on the quantity of traded eider downs, the breeding population has been estimated to have sustained at least 110,000 nests 150 years ago .

In winter, Baffin Bay and the northern and western parts of the Davis Strait become ice-covered, and eiders from the central and northern parts of west Greenland migrate to spend the winter in the southwest Greenland Open Water Area . Furthermore, huge numbers of eiders that breed in eastern Canada (the same subspecies, S. m. borealis) also migrate to winter in this area .

From recent aerial surveys of southwest Greenland (1999), it is estimated that the coastal zone and the adjoining fjords of southwest Greenland support a winter population of 462,794 birds (95% CL: 341,573 – 627,036; Merkel et al. in press). The rather small breeding population in western Greenland can contribute only little to this winter population, and it can be calculated that at least 90% of all common eiders wintering in southwest Greenland originate from Canadian breeding areas .

Hunting and disturbance is, at present, considered the most significant threat to common eiders in western Greenland, and there is growing evidence that the harvest level is not sustainable. It is estimated that at least 57,000 common eiders are bagged annually in Greenland, based on the official hunting bag statistics (Piniarneq). Approximately 80% of these eiders are taken during winter in southwest Greenland, where the majority of the birds are from Canadian breeding grounds (cf. above). Whether this breeding population is also decreasing is presently not known.

According to a computer simulation model, recently developed by Canadian researchers, the west Greenland winter population can sustain a take of c.8% . Presently the take is estimated to be 12%. As a consequence, the model predicts the west Greenland breeding population to decline by 3.2% per year, which is very close to the estimated annual decline of 4% based on field studies.

 

 

The king eider (Somateria spectabilis) population in Western Greenland during autumn and winter determined by aerial surveys and satellite telemetry.

Mosbech, A1)., F. Merkel2) and D. Boertmann1)

1) National Environmental Research Institute, Department of Arctic Environment, P.O. Box 358, Frederiksborgvej 399, DK-4000 Roskilde, Denmark. e-mail: amo@dmu.dk

2) Greenland Institute of Natural Resources, P.O. Box 570, DK-3900 Nuuk, Greenland, Denmark

West Greenland is an important moulting, staging and wintering area for king eiders. Most of these breed in north-eastern Canada and some in north-western Greenland, while king eiders do not breed in West Greenland. To identify key areas and estimate population sizes, the king eiders in West Greenland have been surveyed by aeroplane and tracked by satellite during autumn and winter.

Moulting and post-breeding king eiders in western Greenland were surveyed in late August and early September of 1993, 1994 and 1995. The coastline in the survey area is roughly 13,400 km long and our flight transects totalled approximately 16,500 km. Large numbers of king eiders were observed at a number of remote localities on the west coast of Disko Island and in southern Upernavik. Overall, it is estimated that 30,000 to 40,000 king eiders reside in the coastal zone of western Greenland in late August (Mosbech and Boertmann 1999). Even allowing for a high turnover rate, as different individuals may occupy the moulting areas during the extended period from July to October, this figure can account for only half of a 1950s estimate that 200,000 males and immatures were moulting in western Greenland (Salomonsen 1967, 1968).

The present number of king eiders wintering in south-west Greenland is unknown, but a qualified guess could be 300,000. Based on data sampled during systematic aerial surveys of marine mammals in March 1981 and March 1982, Mosbech and Johnson (1999) estimated that about 270,000 king eiders overwintered on the banks off south-west Greenland (3 surveys with estimates ranging from 135,000 to 345,000). Based on aerial surveys for seabirds in the coastal zone (not including the banks) in March 1999, Merkel et al. (in prep.) estimated 153,000 king eiders (55,000 – 423,000, 95% confidence interval). Due to flock sizes of up to 25,000 birds and a very uneven distribution of flocks both off shore and in the coastal zone, in the large south-west Greenland Open Water Area, it is difficult to get an accurate population estimate. Knowledge of habitat use and movements are needed to plan a dedicated survey covering the key areas both on the banks off shore and in the coastal zone.

To locate autumn staging and winter habitats and describe movements for king eiders in Western Greenland, satellite transmitters were implanted in 10 king eiders (7 males and 3 females) captured between July 31 and August 2 1999 at a moulting site in West Greenland (Mosbech et al. 2001). The king eiders were captured in floating mist nets in Umiarfik, southern Upernavik. Before the end of October, two of the tracked king eiders were reported shot in southern Upernavik. Locations from live birds (omitting the two shot birds) were received over 5.8 ± 0.3 months from three birds with 50g transmitters and over 4.0 ± 2,0 months from 5 birds with 35g transmitters. The tracked birds moulted and stayed in the vicinity of southern Upernavik until October. Six birds were tracked beyond 1 October; of these, five birds went to an offshore bank (Store Hellefiskebanke) about 450 km further south and one bird stayed in southern Upernavik until February. The birds that went to Store Hellefiskebanke had median arrival date October 30 and stayed at Store Hellefiskebanke until the last locations in January 2000. The locations from Store Hellefiskebanke were centred over areas with 23–35 m. water depths, about 50 km from the coast. The daily movements of the birds within Store Hellefiskebanke were relatively small. Ice cover on Store Hellefiskebanke from November to February was variable but never exceeded 9/10 (DMI Ice charts based on Radarsat and NOAA satellite data), and no clear relation between movements of the birds and changes in ice coverage could be seen. It was not previously known that king eiders arrive as early as October to winter on Store Hellefiskebanke. King eider flocks have previously been observed on Store Hellefiskebanke in the month of March. It is recommended that more king eiders from different moulting areas should be tracked by satellite to supplement the small sample size in this study.

Hunting and disturbance is at present considered the most significant threat to king eiders in western Greenland. The official hunting bag statistics (Piniarneq) do not reliably discriminate between common and king eiders. The official annual harvest of eiders is 77,000 (1994-99, Piniarneq), and a study in Nuuk indicates that, in this area, c.32% of the eider harvest is king eiders.

In the breeding areas, in the eastern Canadian Arctic, a ground survey of breeding king eiders in Rasmussens Lowlands, revealed an 86% decrease in king eider abundance from 1976 to 1994-95 (Gratto-Trevor et al. 1998). The cause for this decline is unknown.

CAFF (1997). Circumpolar Eider Conservation Strategy and Action Plan. Conservation of Arctic Flora and Fauna Report. 16 pp.

Gratto-Trevor, C.L., Johnston, V.H. & Pepper, S.T. (1998). Changes in shorebirds and eider abundance in the Rasmussen Lowlands NWT. Wilson Bull. 110: 316-325.

Merkel, F. R., A. Mosbech, D.M. Boertmann, and L. Grøndahl. In prep. Winter seabird distribution and abundance off southwest Greenland, 1999. Submitted.

Mosbech A., and D. Boertmann. 1999. Distribution, abundance and reaction to aerial surveys of post-breeding king eiders (Somateria spectabilis) in western Greenland. Arctic 52: 188-203.

Mosbech A., and S.R. Johnson. 1999 Late Winter Distribution and Abundance of Sea-Associated Birds in Southwest Greenland, Davis Strait, and Southern Baffin Bay. Polar Research 18:1-17.

Mosbech, A., Merkel, F., Flagstad, A. & Grøndahl, L. 2001: Satellitsporing af kongeederfugl i Vestgrønland. Identifikation af raste- og overvintringsområder. Danmarks Miljøundersøgelser. 42 s. -Faglig rapport fra DMU nr. 381

Salomonsen, F. (1967). Fuglene på Grønland. Rhodos, København. 464 pp.

Salomonsen, F. (1968). The moult migration. Wildfowl 19: 5-24.

The common eider Somateria mollissima in Sweden

Leif Nilsson

Department of Animal Ecology, University of Lund, Ecology Building, S-223 62 Lund, Sweden. e-mail: leif.nilsson@zooekol.lu.se

No national surveys of breeding eiders have been undertaken, but a number of regional studies have been published. The total population was estimated to be in the order of 170,000 in the mid-1970s, increasing to around 270,000 in the mid-1980s. There are indications from local and regional studies that the increase has halted and some populations have even decreased recently.

Staging and wintering numbers are low in Sweden as the species mostly leaves the Baltic in the autumn to return in spring. The only larger flocks counted are found on the west coast. September and January indices have been calculated since 1973 and 1967, respectively, but these are only representative for the southern part of the Swedish west coast as no counts were made in the northern part of the west coast (the most important eider area) except in some years. September indices showed a slow increase but the trend from 1985 was markedly decreasing. January indices on the other hand showed an increase, probably as for many other species related to the series of milder winters during the 1990s.

 

 

Population Distribution of Pacific common eiders (Somateria mollissima v-nigrum).

Margaret R. Petersen and Paul L. Flint,

U. S. Geological Survey, Alaska Science Center, 1011 East Tudor Road, Anchorage, Alaska 99503 USA. e-mail: margaret_petersen@usgs.gov

We used satellite telemetry to study the migration routes and wintering areas of two allopatric breeding populations of Pacific common eiders in Alaska: the Yukon-Kuskokwim Delta, and along the western Beaufort Sea coast. Only 5.6 ± 0.6% of 36 females were within the wintering area of the other breeding population. Both populations wintered in the closest available ice-free habitat perhaps to minimise migratory distance. The fact that two Beaufort Sea females wintered in areas used by Yukon-Kuskokwim Delta females creates the potential for gene flow among breeding areas. Yet, we conclude that these two populations are largely geographically isolated throughout the annual cycle and the environmental factors influencing survival and reproduction likely differ between these groups of birds. Thus, regardless of the potential gene flow among breeding populations, we suggest that birds from these two breeding areas should be managed as separate populations.

 

 

 

 

 

Eider Conservation Strategy Implementation: Iceland - Progress report 3

ÆVAR PETERSEN

Icelandic Museum of Natural History, Hlemmur 3, Post Box 5320, IS-125 Reykjavík, Iceland. e-mail: aevar@ni.is

A general overview of the Icelandic common eider population, its status, protection, utilization, and future needs, was compiled in 1997 (Petersen 1997). At CSWG 6 in Ottawa 1999 a matrix was formed, against which the Eider Conservation Strategy action items were weighted. The matrix includes the relevance of the 23 action items for Iceland, whether actions have been completed or not, and if items are in progress. The matrix also included priority rankings for each of the items. The matrix is revised here as towards end of 2001:

Action item

1. Develop international harvest plans 0

2. Establish appropriate harvest rules 0

3. Obtain reliable harvest estimates 0

4. Evaluate the opportunity for guided hunts 0

5. Support egg and down collection programs 3

6. Evaluate risks from human activities 1

7. Encourage non-consumptive uses of eiders 3

8. Identify eiders populations and habitats at risk from oil pollution 2

9. Reduce eider mortality caused by commercial fisheries activities 1

10. Prepare a summary of protected eider areas 1

11. Evaluate existing mechanisms for protecting eider habitat 1

12. Protect additional eider habitat as needed 1

13. Implement other needed protective measures 3

14. Support other eider conservation initiatives 1

15. Ensure co-ordination with other bird conservation plans 1

16. Enlist support of local residents and others interested in eiders 3

17. Solicit periodic evaluation of the Strategy by eider specialists 1

18. Prepare periodic reports summarising accomplishments in

eider conservation 2

19. Ensure that eider conservation projects include an

educational component 1

20. Develop comprehensive research agendas for each species 3

21. Estimate population size, productivity, survivorship, and

movements for each major eider populations 2

22. Study effects of contaminants on eiders 2

23. Develop plans for eiders 3

Key:

0 = Not applicable; 1 = No Action to date but required; 2 = In progress and continuing; 3 = Completed

Various research and other activity has been carried out relevant to the Eider Conservation Strategy since CSWG 7. The major ones are summarised below, giving the action item number for which these are most relevant:

Eider Book: A comprehensive book of common eider biology and eider husbandry as an old tradition and an economic activity, was published in 2001 (Jónsson (ed.) 2001). It includes, among others, chapters, which summarise the present knowledge of eider biology and the research carried out in Iceland, esp. during last two decades. Subjects include e.g. population biology, food, diseases and parasites, contaminants (such as Petersen & Skírnisson 2001). One paper deals with the historical aspect of common eider legislative protection and research and management challenges (Petersen 2001). Much of the book is devoted to the traditional practice of eiderdown collecting and general eider husbandry questions.

Eider Colony Register: In 2001, a database of common eider colonies in Iceland was completed. Altogether about 650 were registered, present and old ones, which have now vanished. Although information on size of some of those colonies exists, for many the present situation is not registered. This information is mostly known locally but has not yet been compiled.

Monitoring of eider colonies: The colony registry provided a basis for selecting representative colonies, using different parameters for stratification, for future monitoring. About 60 were selected, covering the total breeding area, all colony sizes, and local situations, i.e. mainland colonies and island ones.

Banding: Banding activities were continued in especially three colonies, aimed mainly at future survival analyses but also distribution of recoveries. In 2001, the first two recoveries from outside Iceland of Iceland-banded common eiders were reported from Greenland despite thousands of previous banded birds. Previously one hand-raised chick had been recovered in the Faeroes, but this may not have been a representative event for the wild population.

Mating system: Ralph Tiedemann from Germany continued his studies and colleagues on the common eider mating system. The study is based on sampling blood from incubating females, their resulting brood, and as many males as possible. From this paternity and maternity indices are developed.

Eider-down export: eider down, now about 3000 kilos per year, is mostly exported to Denmark, Germany, and Japan, and re-exported elsewhere. Icelandic and American authorities have been co-operating so that down could be exported to USA. The present Endangered Species Act does not allow for the import of listed species or their products, although down was not looked upon as such a product.

National Implementation Plan: A national plan for future work on eider research and management questions, was completed in 2000-2001, and it being published. This identifies the actions needed and priority items. The plan has still to be accepted by the Ministry for the Environment, although some action items have been worked upon, including a monitoring program.

Some references:

Petersen, A. & K. Skírnisson 2001. [The life history of Eiders in Iceland.] Pp. 13-17, 19-45 in: Jónsson, J. (ed.). [Eider and Eider husbandry in Iceland.] Eider-Farmers Association. Mál og Mynd, Reykjavík. 528 pp. (Icelandic).

 

 

Status of the common eider (Somateria mollissima) in Germany and recent developments

Gregor Scheiffarth1, Norbert Kempf2, Bernd Hälterlein3, Petra Potel4

1 Institut für Vogelforschung „Vogelwarte Helgoland", An der Vogelwarte 21, D – 26386 Wilhelmshaven, Germany. e-mail: gregor.scheiffarth@ifv.terramare.de

2 Bernstorffstr. 155, D – 22767 Hamburg, Germany. e-mail: norbert.kempf@web.de

3 Landesamt für den Nationalpark Schleswig-Holsteinisches Wattenmeer, Schloßgarten 1, 25832 Tönning, Germany

4 Nationalparkverwaltung Niedersächsisches Wattenmeer, Virchowstr. 1, D – 26382 Wilhelmshaven, Germany

Common eiders are distributed in Germany over two distinct geographical areas, which offer different habitats to the birds, namely the Baltic and the Wadden Sea. The German breeding population is rather small and has fluctuated around 1,200 breeding pairs since the beginning of the 1980s. Almost all the breeding pairs are confined to the Wadden Sea, with only insignificant numbers along the shore of the Baltic Sea. No long-term trend in breeding numbers could be detected. The species mainly uses the northern and central parts of the German Wadden Sea as moulting grounds. Numbers fluctuate around 200,000 birds with no detectable long-term trend. Along the Baltic coast, no systematic count data exist, however numbers are generally supposed to be low. The wintering population is estimated at 300,000 common eiders with each geographical area holding 50 % in numbers. Along Baltic coasts, numbers decrease eastwards, whereas in the Wadden Sea, no regional trends were detectable. Birds most probably distribute along gradients of prey availability, which change between winters. However, in the winters of 1999/2000 and 2001/2002, mortality was higher than normal along the Wadden Sea coast, with a pronounced east-west gradient in increasing numbers of eiders found dead. No long-term trend in wintering numbers could be detected, however numbers have declined since the winter 1999/2000, resulting in an all time low in January 2002.

Common eider populations in western Scotland: historic and recent trends.

Chris M. Waltho

73 Stewart Street, Carluke, Lanarkshire, Scotland ML8 5BY, UK. e-mail: Clydeeider@aol.com

In the west of Britain, there has been a sustained period of common eider population growth and range expansion for more than a century. This originated in the Inner Hebrides in the second half of the 19th Century and has subsequently spread southwards throughout southwest Scotland, the north of Ireland, northwest England and into Wales by the end of the 20th Century. This expansion of breeding range is shown to have taken place at an average rate of 1.5-3.0 km per annum (15-30 km per decade). In some parts (e.g. Firth of Clyde) this range expansion has taken place as a series of small steps (km within decades), while in others (e.g. north west England and Wales) as large leaps (X 10 km after several decades of population growth).

Population growth has been modelled for the Firth of Clyde at an average 8.5% p.a. for more than 90 years from 1908 to 1999. Within the Clyde, the range expansion was largely complete by c.1970, with only limited localised expansion since. However, the population has continued to grow considerably since then. Counts of the Firth of Clyde during 1996-2001 indicate a fluctuating population of 15,000-20,000 birds in September. The counts suggest that this population is largely comprised of c.12,000-15,000 birds as the Firth of Clyde breeding population (estimated c.3500 breeding females in 1999), supplemented by c.3000 birds from the west Argyll and the Inner Hebrides breeding population (c.60% of that population). However, the trend from the September counts suggests an average decline of -4.5% p.a. from 1996-2001. These annual fluctuations can largely be accounted for by annual variations along the Ayrshire coast; the causes of which are currently unknown.

The sex ratio of this population in September is 60-65% adult males, 35-40% female and yearling males. At an average of 2 males per adult female, this indicates either heavy female mortality (principally on the breeding ground) or very low male mortality, or some combination of both.

It is intended to continue monitoring the Clyde population in September, supplemented by more systematic monitoring of the breeding population. A number of population limitations are considered, but low overall mortality appears to be largely responsible for the sustained population growth.

 

 

Ecology of Steller's eiders and recent assessment of the fishing bycatch in Lithuania

Ramūnas Žydelis

Institute of Ecology, Akademijos 2, Vilnius, Lithuania. e-mail: zydelis@iczm.lt

The winter ecology of wintering Steller’s eiders along the Lithuanian coast was studied in winter 2000/2001, with special emphasis on determining the bycatch of the species in fishing nets. An estimated c.750 Steller’s eiders wintered along the Lithuanian coast in 2000/2001, restricted to a narrow stretch of the coast. Statistical analysis suggested that Steller’s eiders chose habitats characterised by vegetated, hard bottom, shallow water zones. The main foods of these birds were crustaceans, bivalves and gastropods. Highly specific patterns of distribution and food choice were observed in spring, when all Steller’s eiders gathered at herring spawning grounds and fed mainly on fish eggs. The Steller’s eider wintering grounds off the Lithuanian coast fall, however, within an area subject to very intensive gill net fisheries. Numerous cases of bird entanglement in fishing nets were documented. The most dangerous threat to diving birds appeared to be associated with large mesh size nets set for salmon. The most critical period during bird wintering season was March and April, when intensity of fishing is highest. It was estimated that up to 10% of all birds wintering along the Lithuanian coast might drown in fishing nets annually. Besides causing direct mortality of birds, fishing activities in the nearshore zone is also an important source of disturbance to birds. The Steller’s eider is especially sensitive to disturbance, as even under natural conditions, these birds spend a greater proportion of the day feeding. Additional energetic costs incurred by disturbance, together with the loss of foraging time, might adversely affect the ability of birds to satisfy their daily energetic requirements. In conclusion - current conditions of Steller’s eider wintering area at the Lithuanian coast requires immediate conservation measures and proper management. There is some hope that the conservation of Steller’s eiders will improve in future years during the process of expansion of Natura 2000 network.