Dehorter, O. & Tamisier, A. 1998: Hunting vulnerability and wintering strategy among waterfowl in Camargue, France. - Wildl. Biol. 4: 13-21.
Hunting vulnerability of waterfowl species has often been associated with age and sex classes, or with body condition in relation to physiological constraints. In the Camargue, southern France, body weights and daily feeding duration of three dabbling duck species (teal Anas c. crecca, gadwall A. strepera and wigeon A. penelope) have recently been used to isolate three main periods in the winter season (August to March). These periods are characterised successively by high, low and high levels of energy demand, and they constitute the time schedule for a model of wintering strategy. For feeding, birds exploit the productive hunted marshes, mostly during the periods of high energy demand. In this study, we tested the hypothesis that hunting vulnerability can be predicted from these seasonal patterns, being highest when energy demand is highest (at the beginning and at the end of the winter), and being lowest in mid-winter when energy demand is lowest. We used numbers of birds killed (45,000 birds, including the species mentioned above, as well as mallard Anas platyrhynchos and coot Fulica atra) collected from hunting bags in three locations over 12 years, validated on 110,000 killed birds from another location, and adjusted to living (censused) birds. The results do not fit exactly to our predictions. They rather suggest that hunting vulnerability results from a combination of energy demand, habitat selection (both related to wintering strategy), chronology of migration and trophic status of duck species (granivorous vs herbivorous). At the beginning of the winter season, granivorous species, the first to arrive, are inexperienced to hunting, have a high energy demand and are highly vulnerable. At the middle of the winter season, when energy demands are low, the birds can escape from hunting to refuge areas. Meanwhile, herbivorous species, still arriving, must spend more time on feeding (vegetative food contains less energy than seeds) on productive hunted marshes; they suffer high hunting vulnerability from hunters who shift from granivorous to herbivorous species. At the end of the winter season, granivorous and herbivorous species rely on hunted areas for feeding and are very vulnerable. However, hunting vulnerability of a given species is lowered since hunting pressure during that last period of winter is shared among a maximum number of game species, some of which are migrating back from Africa.
Key words: Camargue, energy demand, hunting, vulnerability, waterfowl, wintering strategy
Olivier Dehorter & Alain Tamisier, Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, 1919 Route de Mende, F - 34293 Montpellier Cedex 5, France - e-mail: email@example.com
Received 6 May 1996, accepted 9 October 1997
Associate Editor: Hannu Pöysä