Flemming Merkel

Can Local Ecological Knowledge Contribute to Wildlife Management? Case Studies of Migratory Birds

Sound management of wildlife species, particularly those that are harvested, requires extensive information on their natural history and demography. For many global wildlife populations, however, insufficient scientific information exists, and alternative data sources may need to be considered in management decisions. In some circumstances, local ecological knowledge (LEK) can serve as a useful, complementary data source, and may be particularly valuable when managing wildlife populations that occur in remote locations inhabited by indigenous peoples. Although several published papers discuss the general benefits of LEK, few attempt to examine the reliability of information generated through this approach. We review four case studies of marine birds in which we gathered LEK for each species and then compared this information to empirical data derived from independent scientific studies of the same populations. We then discuss how we attempted to integrate LEK into our own conservation and management efforts of these bird species with variable success. Although LEK proved to be a useful source of information for three of four species, we conclude that management decisions based primarily on LEK, in the absence of scientific scrutiny, should be treated with caution.

Prevalence of marine debris in marine birds from the North Atlantic.

Marine birds have been found to ingest plastic debris in many of the worlds oceans. Plastic accumulation data from necropsies findings and regurgitation studies are presented on 13 species of marine birds in the North Atlantic, from Georgia, USA to Nunavut, Canada and east to southwest Greenland and the Norwegian Sea. Of the species examined, the two surface plungers (great shearwaters Puffinus gravis; northern fulmars Fulmarus glacialis) had the highest prevalence of ingested plastic (71% and 51%, respectively). Great shearwaters also had the most pieces of plastics in their stomachs, with some individuals containing as many of 36 items. Seven species contained no evidence of plastic debris. Reporting of baseline data as done here is needed to ensure that data are available for marine birds over time and space scales in which we see changes in historical debris patterns in marine environments (i.e. decades) and among oceanographic regions.

Winter seabird distribution and abundance off south-western Greenland, 1999

South-western Greenland constitutes an internationally important wintering area for many seabird species. Several species of management concern have a predominantly near-coastal distribution, though available information about seabird numbers is mostly confined to offshore waters. Here we report on extensive aerial surveys conducted in March 1999, covering the coastal waters (up to 15-20 km from the mainland coast) and fjords of south-west Greenland. The most widespread and numerous species were estimated as 463 000 common eiders (Somateria mollissima), 153000 king eiders (S. spectabilis), 125000 thick-billed murres (Uria lomvia), 94 000 long-tailed ducks (Clangula hyemails), and 12 000 black guillemots (Cepphus grylle). A total of 19 bird species were recorded. The estimates for common eider and long-tailed duck approximately represent the entire winter population in south-western Greenland while estimates for the other species represent only an unknown proportion since their distribution continues further offshore. Waters around Nuuk and within the Julianehåbsbugten (Julianehåb Bay) area were identified as areas of high seabird density. A large proportion of the common eider population was aggregated in the fjord systems (22%), calling attention to the importance of fjords for this species. In contrast, pelagic seabird species appear to be absent from the fjords. The large winter population of common eider reveals the importance of south-western Greenland as a key wintering area for the eastern Canadian breeding population. The western Greenland breeding population is the only other contributor, probably amounting to no more than 15 000 pairs.

Evaluating the sustainability of harvest among northern common eiders Somateria mollissima borealis in Greenland and Canada

Sustainable harvest, the extraction of game without affecting population viability, is a desirable approach to the use of wildlife. However, overharvest has been responsible for the decline of many wildlife populations globally, so there is an urgent need to balance human requirements while avoiding the severe depletion of wild populations. Northern common eiders Somateria mollissima borealis are heavily hunted in Canada and Greenland, but the effect of this intensive harvest has not been examined. We developed a population model to investigate the sustainability of the reported harvest, which consisted of two wintering areas in Greenland and Atlantic Canada and three breeding populations. The model indicated that harvest in Atlantic Canada was sustainable, but a number of conditions could lead to slow declines. In contrast, the annual winter harvest of 55,000–70,000 eiders reported during 1993–2000 in Greenland was not sustainable, and this conclusion held under a wide range of alternate conditions. The model indicated that harvest during late winter may have a greater effect on populations than harvest in early winter. We further refined the model to assume that at some low population level the success of hunters would decline and that harvest became a function of population size (a rate). This scenario had the expected and undesirable result of stabilizing populations at very low levels. Overall, our model suggests that the high harvest reported in Greenland during 1993–2000 endangers the sustainable use of the northern common eider population and that management actions are required. Common eider harvest levels in Greenland should be reduced by at least 40% of the 1993–2000 levels to stop projected declines, and allow for recovery of the decimated Greenland breeding population. Encouragingly, new hunting regulations were introduced in Greenland in 2002–2004, and harvest levels appear to be decreasing. If these harvest reductions continue, our population model could be used to re-evaluate the status of populations in the two countries.

The diet of common eiders wintering in Nuuk, Southwest Greenland

Southwest Greenland provides wintering grounds for 70% (∼460,000) of the northern common eider (Somateria mollissima borealis) population. From 241 gullet samples (esophagus and proventriculus content) collected over three winters (1999–2002) near Nuuk, we identified 39 species consumed by the eiders. In contrast to studies elsewhere, fresh mass of the diet was dominated by soft-bottom species: the bivalve Mya eideri (32.8%) and the polychaete Pectinaria spp. (24.2%). The hard-bottom blue mussel (Mytilus edulis), usually the dominant prey of common eiders, was only the fourth most important diet species (7.5%). Overall, bivalves accounted for 56% of the diet. Twenty-seven prey species were minor foods with aggregate fresh mass of only 5.5%. Diets of males and females were similar, whereas juveniles consumed greater mass of crustaceans and less of bivalves. Diet diversity was higher in mid-winter than late winter, and higher in coastal habitats than in fjords. Within one important wintering area the results indicate that optimal size of blue mussels may be depleted over winter.

Light-induced bird strikes on vessels in Southwest Greenland.

Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2-3 winters (2006-2009) from navy vessels, cargo vessels and trawlers (total n=19). Forty-one incidents were reported: mainly close to land (<4 km, 78%), but one as far offshore as 205 km. Up to 88 birds were reported killed in a single incident. All occurred between 5p.m. and 6a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland.

The significance of Southwest Greenland as winter quarters for seabirds

The coastal and offshore waters of Southwest Greenland are internationally important winter quarters for seabirds. We crudely estimate a minimum of 3.5 million seabirds using the region in winter, mainly from Arctic Canada, Greenland and Svalbard, with smaller numbers also from Alaska, Iceland, mainland Norway and Russia. The most numerous species are Common Eider Somateria mollissima , King Eider S. spectabilis , Brunnichs Guillemot Uria lomvia and Little Auk Alle alle . The most immediate threat to the seabirds in Southwest Greenland is hunting, and current levels of usage of the Greenland breeding populations of Brunnichs Guillemot and Common Eider are considered unsustainable. Conservation measures are required for these populations.

The diet of king eiders wintering in Nuuk, Southwest Greenland, with reference to sympatric wintering common eiders

Coastal and offshore waters of Southwest Greenland are internationally important wintering areas for king eiders (Somateria spectabilis) breeding in eastern Canadian Arctic and in northwestern Greenland. This paper presents the first assessment of their winter diet. Based on esophageal-proventricular samples from 26 females (13 juveniles and 13 older birds) and 15 males (11 juveniles and four older birds) collected in 2000–2002 (November–May) in coastal waters of Nuuk, we identified 28 prey species. The diet consisted of almost equal proportions (aggregate fresh mass) of polychaetes, echinoderms, crustaceans and molluscs. The dominant prey species were Pectinaria spp. (26.8%), Strongylocentrotus droebachiensis (18.4%), Mya eideri (11.2%) and Hyas araneus (9.7%). The polychaetes have previously been identified as important prey for eiders in Greenland, but apparently not outside Greenland. Compared with a diet study of common eiders Somateria mollissima from the same wintering area, the king eiders consumed significantly less bivalves and significantly more echinoderms. This difference corresponded with observations that common eiders were feeding in shallow waters, while king eiders were feeding in deeper waters farther from the shore. Benthic surveys are needed to confirm that diet corresponds with prey availability.

Evidence of Recent Population Recovery in Common Eiders Breeding in Western Greenland

Abstract Severe population declines were reported for common eiders (Somateria mollissima) in western Greenland over the period 1960–2000. A monitoring program, concurrent with more restrictive hunting regulations on common eiders, revealed breeding numbers increasing by 212%, from 2,558 active nests in 2000 to 7,982 nests in 2007. Though it was not possible to directly link harvest reduction and population growth in West Greenland, a similar increase in breeding numbers in Canada was correlated with the harvest reduction in Greenland and linked to increasing adult survival and recruitment of first-time breeders, and a similar explanation is suggested for West Greenland. The study emphasizes that appropriate restrictions in hunting can be efficient in wildlife management and that common eiders can sustain dramatic rates of increase during population regrowth. It also shows that cost-efficient monitoring programs can be established through cooperation with local residents.

An evaluation of methods used to estimate carcass composition of common eiders Somateria mollissima

Abstract To examine how endogenous reserves may influence avian life history, it is often necessary to quantify carcass composition. However, proximate analyses are expensive, time-consuming and difficult to perform under field conditions. Consequently, carcass composition is often estimated from easily measured data. We evaluate methods of estimating carcass composition of the common eider duck Somateria mollissima. We measured, dissected and completed proximate analyses of 92 eiders. Predictive models were derived using multiple regressions of 70 birds, while the remaining 22 were used as an independent test of the models. Each models accuracy was evaluated by comparing estimates against known values of protein and lipids, using root mean square error (RMSE). Abdominal and leg fat pad mass were highly correlated with total lipid (r = 0.92), and body mass was highly correlated with total protein (r = 0.80). Models that used body mass, fat depots and/or muscle group data were the most accurate (lipids adjusted R2 = 0.93, RMSE = 14.60; protein adjusted R2 = 0.74, RMSE = 11.14). By using these equations it is possible, using dissection data, to accurately estimate carcass composition of eiders. If dissection data are not available, one can still estimate carcass composition using equations that require only morphometrics although in our lipid analysis such equations had relatively low accuracy (lipids adjusted R2 = 0.54, RMSE = 32.74).