Eileen C. Rees

Changes in Tundra Swan Cygnus columbianus bewickii distribution and abundance in the Yangtze River floodplain

PEIHAO CONG, LEI CAO, ANTHONY D. FOX, MARK BARTER, EILEEN C.REES, YONG JIANG, WEITOU JI, WENZHONG ZHU and GUOXIAN SONGApproximately 75% of the East Asian Flyway Tundra Swan Cygnus columbianus bewickiipopulation winters in the Yangtze River floodplain, China. Historically the species was morewidely distributed throughout the floodplain but now most of the population is confined to fivewetlands in Anhui Province and to Poyang Lake in Jiangxi Province, where the majority (up to113,000 birds) occur. Within-winter counts suggest that swans congregate at Poyang Lake beforedispersing to other sites later in the winter. Counts show large between-year fluctuations,but suggestdeclines at Shengjin and Fengsha La kes (both in Anhui) during the last five years. Declines atShengjin Lake are likely due to decreases in subme rged vegetation (particularly tuber-producingVallisneria, a major food item) perhaps linked to eutrophication. Range contractions throughout thefloodplain may also be linked to reductions in submerged vegetation coverage elsewhere. Changes inwater quality and lake hydrology post-Three Gorges Dam may have adversely affected submergedvegetation productivity. Key information needs for the effective implementation of conservationmeasures for Tundra Swans include: ( 1) annual surveys of all major wintering sites throughout eachwinter to establish the importance of different sites during the non-breeding period; ( 2)moreinformation on swan diets at important sites; and ( 3) an assessment of adverse effects of water qualityand lake water levels post-Three Gorges Dam on submerged vegetation productivity at Poyang Lakeand other important sites.

Has winter body condition varied with population size in a long-distance migrant, the Bewick’s Swan (Cygnus columbianus bewickii)?

Assessments of body condition can provide useful information on changes in the state of individuals within a population, which may in turn help to inform conservation efforts. For example, decreases in body condition over time can indicate reduced food resources. Mass and skull length measures recorded for 195 adult and 467 first winter (cygnets) Bewick’s Swans (Cygnus columbianus bewickii) at wintering sites in the UK between winters 1966/1967 and 2017/2018 therefore were analysed to determine whether a ca. 40% decline in numbers in the Northwest European Bewick’s Swan population between 1995 and 2010 corresponded with poorer body condition from the mid-1990s onwards. Parents and siblings were known for all individuals, allowing us to account for shared genetic factors and rearing environment in our analysis. We used linear mixed-effects models and an information-theoretic approach to test different models of temporal variation in scaled body mass index (SBMI). Within our study population, although SBMI values varied both within and between years, we found no evidence of any directional trends in body condition. Of our competing time models of swan SBMI, a model in which age-specific body condition was constant over time received the greatest support in the data. Body condition was greater for adults than cygnets, but did not vary between sexes or wintering sites. Our findings suggest no connection between the recent declines in population size and body condition. Population decline is therefore unlikely to be caused by inadequate food supplies.

Mapping critical habitat of waterbirds in the Arctic for risk management in respect of IFC PS6

Economic development and energy exploration are increasing in the Arctic. Important breeding habitats for many waterbird species, which have previously been relatively undisturbed, are now being subjected to these anthropogenic pressures. The conservation of the habitats and the species they support is a significant challenge for sustainable development. Even if governments and corporates operating in this fragile environment are committed to sustainable development, there is little information available to avoid, mitigate and manage environmental risk and impacts. Taking a risk management perspective, we followed the International Finance Corporations’ (IFC) Performance Standard 6 (PS6) criteria on Environmental and Social Sustainability and developed an approach to identify “critical habitat”, as defined in IFC PS6, for waterbird species breeding in the Arctic. While the range of these waterbirds is roughly known, more accuracy is needed for proper risk assessment. We have therefore gone a step further by modelling suitable habitat within these ranges. Depending on the relevance of the species for IFC PS6 and the level of certainty we separated the classes likely and potential critical habitat. We tested the approach for Russian breeding populations of five Anatidae species (White-fronted Goose Anser albifrons, Lesser White-fronted Goose Anser erythropus, Brent Goose Branta bernicla, Redbreasted Goose Branta ruficollis and Bewick’s Swan Cygnus columbianus bewicki). Likely critical habitats were identified through a review of literature and available data for these waterbird species and multi-species congregations. To address the information gap for most of the Russian Arctic a species distribution modelling approach was used. The outputs of this approach were labelled as potential critical habitat, indicating the lower level of certainty than likely critical habitat. Based on existing information the amount of likely critical habitat is estimated to be at least x,xxx,xxx km2. For the five Anatidae species, X,XXX,XXX km2 potential critical habitat was identified; 95% of these areas were outside of the area boundaries of likely critical habitat for the species. Insufficient data in the east of the study area did affect the results, as some areas known to support breeding populations were not identified as suitable. Conversely, species’ distributions may be overpredicted in other areas; It should also be recognized that the analyzed species currently have depressed populations and may therefore only utilize a proportion of suitable habitat available. For risk assessment purposes however, it is better to predict false positives, rather than false negatives. The study indicates that there are large areas in the Arctic that are potentially important for each of the Anatidae species modelled, but are not yet recognised as key important areas. The results confirm that there is still much to learn about waterbird distribution and abundance in the Russian Arctic. Synthesis and applications The critical habitat maps produced do not just provide a new source of information for the economic development sector, but provide it in a way that is relevant to the sector and directly applicable. The maps are useful for initial risk assessments of potential developments, to identify likely impacts and to consider mitigation options, in accordance with IFC PS6. Risk assessors should exercise caution and detailed surveys for any development in areas predicted to be suitable for each species should be carried out.