Bart A. Nolet

Predicting the environmental impact of a proposed development is notoriously difficult, especially when future conditions fall outside the current range of conditions. Individual-based approaches have been developed and applied to predict the impact of environmental changes on wintering and staging coastal bird populations. How many birds make use of staging sites is mostly determined by food availability and accessibility, which in the case of many waterbirds in turn is affected by water level. Many water systems are regulated and water levels are maintained at target levels, set by management authorities. We used an individual-based modelling framework (MORPH) to analyse how different target water levels affect the number of migratory Bewick's swans Cygnus columbianus bewickii staging at a shallow freshwater lake (Lauwersmeer, the Netherlands) in autumn. As an emerging property of the model, we found strong non-linear responses of swan usage to changes in water level, with a sudden drop in peak numbers as well as bird-days with a 0.20 m rise above the current target water level. Such strong non-linear responses are probably common and should be taken into account in environmental impact assessments.

Population declines among migratory Arctic-breeding birds are a growing concern for conservationists. To inform the conservation of these declining populations, we need to understand how demographic rates such as breeding success are influenced by combinations of extrinsic and intrinsic factors. In this study we examined inter-annual variation and long-term trends in two aspects of the breeding success of a migratory herbivore, the Bewick's swan Cygnus columbianus bewickii, which is currently undergoing a population decline: 1) the percentage of young within the wintering population and 2) mean brood size. We used an information-theoretic approach to test how these two measures of productivity were infl uenced over a 26 yr period by 12 potential explanatory variables, encompassing both environmental (e.g. temperature) and intrinsic (e.g. pair-bond duration) factors. Swan productivity exhibited sensitivity to both types of explanatory variable. Fewer young were observed on the wintering grounds in years in which the breeding period (May to September) was colder and predator (Arctic fox) abundance was higher. Th e percentage of young within the wintering population also showed negative density-dependence. Inter-annual variance in mean swan brood size was best explained by a model comprised of the negative degree days during the swan breeding period, mean pair-bond duration of all paired swans (i.e. mean pair duration), and an interaction between these two variables. In particular, mean pair duration had a strong positive effect on mean brood size. However, we found no long-term directional trend in either measure of breeding success, despite the recent decline in the NW European population. Our results highlight that inter-annual variability in breeding success is sensitive to the combined eff ects of both intrinsic and extrinsic factors.

... Kramer (1988) used a marginal value approach to determine how much time such a diver, given the time needed to ... ACKNOWLeDGMeNTS We thank Taivo Kastepold and Kaja Lotman (Matsalu Looduskaitseala) for permission to work in Matsalu Nature Reserve, Leho Luigujõe ...

ABSTRACT Background/Question/Methods The spring migration is regarded as an energetic bottleneck in the annual cycle of capital breeders because they must accumulate energy and nutrients in preparation for further migration and breeding. Furthermore, because of seasonality in availability and quality of food recourses in staging areas, each stopover site offers a different set of constraints. En route to their breeding grounds, the Svalbard population of pink-footed geese stops twice, in mid- and northern Norway. Each stopover site provides different combinations of energy-rich and nutrient-rich resources. The aim of this study is to calculate the metabolizable energy intake of geese in mid Norway – the last site at which both resource types are present. The estimation of the daily energy budget was based on GPS tracking of individual birds and activity budgets derived from flock scans. Results/Conclusions The daily metabolizable energy intake was positive for all individuals and on average geese gained 1.6 more energy than they spent. However, the daily metabolizable energy was still below the maximum daily fuel deposition rate calculated for the studied species, which could be due to digestive constraints, food availability and the increased cost of flying with increased body mass. In mid-Norway habitat use by the geese was not proportional to habitat availability, and variations in energy intake were not related to the relative availability of resources with different energetic content and digestibility and the time available for feeding. Energy intake on a given day was correlated to the energy intake in the previous days. This trend was the same throughout the stopover season suggesting that foraging behaviour is a chain of decisions taken on a daily basis, although overall energy intake probably mediates decision-making. The total metabolizable energy intake was correlated with the time spent at the studied site. We conclude that mid-Norway does not currently serve as an energetic bottleneck, although the increased flying costs due to frequent disturbance and increased energy expenditure due to intra- and inter-specific competition may alter this situation in the future.

ABSTRACT tAccording to the green wave hypothesis, herbivores follow the flush of spring growth of forage plantsduring their spring migration to northern breeding grounds. In this study we compared two green waveindices for predicting the timing of the spring migration of avian herbivores: the satellite-derived greenwave index (GWI), and an index of the rate of acceleration in temperature (GDDjerk). The GWI was cal-culated from MODIS normalized difference vegetation index (NDVI) satellite imagery and GDDjerk fromgridded temperature data using products from the global land data assimilation system (GLDAS). To pre-dict the timing of arrival at stopover and breeding sites, we used four years (2008–2011) of tracking datafrom 12 GPS-tagged barnacle geese, a long-distance herbivorous migrant, wintering in the Netherlands,breeding in the Russian Arctic. The stopover and breeding sites for these birds were identified and therelations between date of arrival with the date of 50% GWI and date of peak GDDjerk at each site were ana-lyzed using mixed effect linear regression. A cross-validation method was used to compare the predictiveaccuracy of the GWI and GDDjerk indices. Significant relationships were found between the arrival datesat the stopover and breeding sites for the dates of 50% GWI as well as the peak GDDjerk (p < 0.01). The goosearrival dates at both stopover and breeding sites were predicted more accurately using GWI (R2cv= 0.68,RMSDcv= 5.9 and R2cv= 0.71, RMSDcv= 3.9 for stopover and breeding sites, respectively) than GDDjerk.The GDDjerk returned a lower accuracy for prediction of goose arrival dates at stopover ( R2cv= 0.45,RMSDcv= 7.79) and breeding sites (R2cv= 0.55, RMSDcv= 4.93). The positive correlation between the abso-lute residual values of the GDDjerk model and distance to the breeding sites showed that this index ishighly sensitive to latitude. This study demonstrates that the satellite-derived green wave index (GWI)can accurately predict the timing of goose migration, irrespective of latitude and therefore is suggestedas a reliable green wave index for predicting the timing of avian herbivores spring migration.

... This has been experimentally demonstrated in starlings (Sturnus vulgaris) feeding with their heads fully immersed in high cups (Templeton and Giraldeau 1995). ... We would like to thankBart van Lith and Koos Swart for their help with the experiments. ...

... Wildfowl, Suppl. 1: 238-248. Blaxter, K. 1989. Energy Metabolism in Animals and Man. ... Biol. 199: 1613-1618. Pennycuick, CJ, Einarsson, 0., Bradbury, TAM and Owen, M. 1996. Migrating Whooper Swans Cygnus cygnus: satellite tracks and flight performance calculations. ...

... Kramer (1988) used a marginal value approach to determine how much time such a diver, given the time needed to ... ACKNOWLeDGMeNTS We thank Taivo Kastepold and Kaja Lotman (Matsalu Looduskaitseala) for permission to work in Matsalu Nature Reserve, Leho Luigujõe ...

The efficiency in which high-density food patches are found is determined by the way foragers move between patches. In this study we explore the effect of social interactions on the foraging path, in particular the distance moved between patches. We studied Bewick’s Swans Cygnus columbianus bewickii that foraged on belowground tubers of Fennel Pondweed Potamogeton pectinatus. We accurately mapped the

1. Data on swimming energy expenditure of 30 submerged and nine surface swimmers, covering different swimming styles and taxonomic groups, are selected from the literature. 2. The costs of transport at the optimum speed are compared and related to body mass and Re numbers. 3. Fish and turtles use relatively less and most surface swimmers slightly more energy than the other submerged swimmers; man and mink are poorly adapted to swimming. 4. The metabolic rate in W at optimum speed is approximately equal to the body mass in kg for fish and turtles and three times the mass figure for the other submerged swimmers.

ABSTRACT Prey populations, patterns of availability, and dispersion of prey can have farreaching effects on numbers and range-sizes of terrestrial Carnivora (Macdonald, 1983; Kruuk & Parish, 1982; Kruuk & Macdonald, 1985). These parameters may therefore also affect populations of otters Lutra lutra, living in the sea around Shetland, U.K., as well as populations of fish-eating birds there. This paper presents observations on fluctuations in numbers and activity of several species of demersal fish, over a 3½ year period, along a coast in Shetland. It aims to provide information on the distribution and availability of these species to some predators, especially to the otter, but also to the heron Ardea cinerea, the black guillemot Cepphus grylle and others.