The Arctic is an extreme environment for many organisms. The primary objective of Theme C has been to make a comprehensive investigation and analysis of bird migration ecology in High Arctic North America. The approach is interdisciplinary and based on an integration of studies of migration routes and patterns, orientation, energetics and genetics. Studies of moths and butterflies on the tundra and their special adaptations are also included in the theme.

For birds, orientation and navigation have special complications at high latitudes, where the magnetic field may be difficult to use, especially near the magnetic North Pole. Stars are not visible, and the internal clock is easily shifted out of phase with local time when the animals move even short distances in east-west directions. The detailed routes of the migrants are largely unknown, and the high latitudes allow, for the human eye, unorthodox and exciting solutions. The summers are so short that the time available for breeding, moult and migratory preparations may not be sufficient. Birds may therefore need to bring nutrients and energy from further south, and leave in the autumn as soon as their offspring are independent or the wings of the young can carry them aloft. Thermoregulatory costs are high due to the cold and will to a large extent limit the energy available for other needs. Another focus of our work has been the geographical occurrence of species and populations with special emphasis on waders and also on birds of prey, including skuas. Studies of birds of prey and skuas were planned and carried out in close collaboration with Theme A, interactions between plants, herbivores and predators.

The ecology of migrating birds in the Arctic is fascinating in itself and study of migrating birds living in extreme conditions will help us understand the constraints acting on migratory birds in general. Furthermore, these studies complement previous investigations in northernmost Europe and Siberia, and will make it possible to approach these questions in a circumpolar perspective.

The Arctic is special for moths as well. One important feature of the Arctic is that the numbers of insect-eating birds are comparatively low, and bats, formidable enemies in warmer regions, are completely absent. In temperate and tropical regions, moths have an array of defences, such as colouring and ultra-sound detection, against predators. If moths have adapted to the Arctic environment, have they lost these defences in the evolutionary process, using their precious resources on other needs?

Approach

Thirteen scientists participated in Theme C during the expedition, seven on leg 1 and six on leg 2. In addition, two persons were based in Inuvik the whole summer, conducting bird orientation experiments in parallel to those carried out by the ship-based scientists.

We addressed the many questions using a multitude of methods, from purely visual observations to the latest and most advanced techniques. Visual observations were carried out both from the ship and ashore. However, since most bird migration goes on at heights of several hundreds and thousands of metres, out-of-range even for binoculars, we used a tracking radar that was located on the ship. Two persons manned the radar at all times when the ship was still, mainly when the rest of the scientists were on the tundra. In this way, observations from ashore and radar observations from the ship complemented each other and furnished a good picture of migration activities, migratory directions and the species involved (which is normally not noted by the radar). Orientation experiments were conducted with captured migrants (white-crowned sparrows) displaced with the ship, while simultaneous experiments were carried out at the capture site at Inuvik, exploring the birds’ capacity for orientation and navigation under what must be extraordinarily difficult conditions.

Historically, sampling on an Arctic expedition was equivalent to collecting whole animals. Our ambition was to collect scientifically sound information whilst keeping the animals alive. From the more than 300 birds trapped we collected blood, feathers and preen-gland waxes. From these samples we can deduce exciting information about migration routes, population differences and physiological parameters on the bases of analyses of stable isotopic ratios and of rapidly evolving DNA-regions (mini-or microsatellites or mitochondrial DNA).

The expedition was very successful indeed, and all parts of our programme obtained valuable results and samples as can be seen from the cruise reports (although we failed to capture the birds that we had planned for satellite based radio telemetry studies). Theme C researchers are now in the midst of an inspiring phase of the work, evaluating and analysing the extensive data from radar tracking, orientation experiments, respirometry, fuel deposition estimates and DNA and isotope samples etc. We hope and believe that there is a very good chance that a new picture of the adaptations shown by the migrating birds and the moths of the North American tundra will emerge when these results are put together and considered in relation to our previous studies in Siberia.