Tracking devices and bio-loggers provide crucial information on the ecology and behaviour of birds in their natural environment. An optimal tracking system should be lightweight, measure three-dimensional locations, enable flexible measurement schemes, transmit data remotely and measure environmental variables and biological parameters of the individual. Giving full consideration to the traits of birds and the constraints of technology, we have developed a GPS tracking system that attempts to achieve most of the aspirations of an optimal tracking system for free ranging birds without the need to recapture them. Here, we describe the design, performance and limitations of the system. We also present measurements on the tracked Lesser Black-backed Gull Larus fuscus to show how such a system can generate new opportunities for research at multiple scales. The GPS tracker weighs 12 g and includes a GPS receiver, micro-processor, 4 MB of memory for data storage, solar panel and battery. It has a tri-axial accelerometer to monitor behaviour. To maximize flexibility, it is equipped with a radio transceiver for bidirectional communication with a ground-based antenna network, which enables data to be downloaded and new measurement schemes to be uploaded remotely. The system facilitates a multi-scale approach to studying bird movement, from fine-scale movements (3-s measurement intervals) to long-distance migratory movements (intervals of 20-30 min) of the same individual. We anticipate that flexible tracking systems that enable researchers to optimize their measurement protocols will contribute to revolutionizing research on animal behaviour and ecology in the next decade.

Barrett, R. T., Camphuysen, C. J., Anker-Nilssen, T., Chardine, J. W., Furness, R. W., Garthe, S., Hüppop, O., Leopold, M. F., Montevecchi, W. A., and Veit, R. R. 2007. Diet studies of seabirds: a review and recommendations. – ICES Journal of Marine Science, 64. We review the different methods that are used to collect dietary data from marine birds. We consider their limitations and practicalities and emphasize critical data gaps in our knowledge of the feeding ecology of seabirds (na mely diets outside breeding seasons). To enhance comparability of findings among studies, species, and oceanographic regions, we make recommendations on standards for the reporting of results in the literature.

Most types of fishery produce discards and offal in considerable quantities which are fed upon by seabirds. This paper demonstrates the importance to seabirds of fishery waste in the North Sea. The total amount of fishery waste in the North Sea region is estimated at 62800 t of offal, 262200 t of roundfish, 299300 t of flatfish, 15000 t of elasmobranchs and 149700 t of benthic invertebrates per year, representing 4 % of the total biomass of fish and 22% of the total landings This equals an energy value of about 3.4 X 10" kJ. Beam trawl f~sheries discharge discards at the highest rates of all fishing fleets. Their discard fraction is dominated by flatfish which are less favoured by seabirds because of their shape. In contrast, the amounts of discards from pelagic and gadid fisheries are less, but fish species and lengths are more appropriate as food for seabirds. The number of seabirds potentially supported by fishery waste in the North Sea is estimated to be roughly 5.9 million individuals in an average scavenger community (composition in proportion to the seasonal abundance of scavenging species). During expenmental discard studies, the proportions of fishery waste consumed by seabirds was calculated. We estimated that the mass of discards and offal consumed by birds during our study amounted to 55000 t of offal, 206000 t of roundfish, 38000 t of flatfish, 2000 t of elasmobranchs and 9000 t of benthic invertebrates.

Summary1. Upcoming reform of the European Union (EU) Common Fisheries Policy will be the biggest change in European fisheries management for a generation. A central plank of this reform is a proposed ban on discards, to aid the creation of economically and environmentally sustainable fisheries. This, together with a global trend for declining discards, may have unforeseen knock-on consequences for the large number of scavenging seabirds that consume this plentiful subsidy. 2. Discards have shaped many aspects of seabird foraging, distribution and population dynamics. Here, we review these effects and consider the potential for both negative and positive impacts of discard reforms for seabirds, with particular focus on the EU, and propose recommendations for ongoing research and conservation. 3. EU seabird scavengers are dominated by a relatively small number of large generalist taxa. Many of these occur at globally significant numbers within the EU, but may be able to buffer a decline in discards by switching to feed on alternative foods. 4. A discard ban may have negative consequences by creating a food shortage for scavenging birds. Some species may offset this by feeding more on other birds, with potentially negative population-level impacts, or by moving into novel environments. 5. Benefits of a discard ban may be a reduction in seabird bycatch in fishing gears, as well as a reduction in populations of large generalist species that currently dominate some seabird communities. 6. Synthesis and applications. Reform of the Common Fisheries Policy and global discard declines are essential components towards creating sustainable fisheries, but may have both detrimental and beneficial effects on seabird communities. The nature of these impacts is still poorly understood, highlighting the need for detailed long-term seabird monitoring, as well as building resilience into populations through policy measures that incorporate remedial action on major seabird conservation priorities. Research should focus on understanding how seabird foraging, in terms of functional responses and searching behaviour, is influenced by both changing discards and natural fish prey availability, and how they impact upon fitness. It is also essential to link individual-level responses with population-, community-and ecosystemlevel change. Understanding these links is fundamental to ongoing seabird management and conservation, and an ecosystem-based approach to fisheries management.

as both sexes foraged substantially in competitive settings around fishing vessels, but in different habitats. Females accessed a wider variety of resources and a broad prey spectrum, by exploring a whole suite of foraging opportunities and habitats nearer the colony. Different behavioural strategies (a combination of individual specialisation and sexual segregation) during breeding could reduce intra-specific resource competition, competition between the sexes (and hence within a pair), or alternatively, reduce the risk of unbalanced food provisioning.