What type of lean ducks do hunters kill? Weakest local ones rather than migrants
Guillemain, M., Fritz, H., Johnson, A.R. & Simon, G. 2007: What type of lean ducks do hunters kill? Weakest local ones rather than migrants. - Wildl. Biol. 13: 102-107.
An earlier study in western France showed that birds shot around protected areas had a lower body mass than birds remaining in nature reserves, but it was impossible at that time to distinguish whether shot birds were leaner because they were exhausted and ignorant migrants, or whether there was simply a body-condition bias making the leaner individuals of the area more likely to be shot. To test these hypotheses, we used body mass at ringing from close to 5,000 teal Anas crecca in the Camargue, southern France. Distinguishing between 'resident' birds recaptured alive in the same protected area at least once during the month following ringing, 'locally shot birds' hunted in the Camargue and 'migrants' hunted out of the Camargue area during the same period, we could not detect any significant difference between the average body mass of 'residents' and 'migrants', whereas locally shot birds were generally lighter. This suggests that migration is not the reason why hunters generally shoot lean ducks around nature reserves. Conversely, these results support the idea that some mechanisms, maybe linked to competition and dominance relationships between birds in protected areas, make the leaner teal more likely to get killed by hunters. Whatever the mechanism involved, this pattern suggests that carrying capacity was reached in the protected areas, a situation calling for appropriate habitat management.
Key words: Anas crecca, body condition bias, body mass, migration
Matthieu Guillemain Office National de la Chasse et de la Faune Sauvage, CNERA Avifaune Migratrice, La Tour du Valat, Le Sambuc, F-13200 Arles, France - e-mail: m.guillemain@oncfs.gouv.fr
Hervé Fritz*, Centre d'Etudes Biologiques de Chizé, CNRS UPR 1934, F-79360 Beauvoir sur Niort, France - e-mail: fritz@biomserv.univ-lyon1.fr
Alan R. Johnson & Géraldine Simon, Station Biologique de la Tour du Valat, Le Sambuc, F-13200 Arles, France - e-mail addresses: alanJHSN@aol.com (Alan R. Johnson); simonegeraldine@yahoo.fr (Géraldine Simon)
*Present address: LBBE, CNRS UCBL UMR 5558, Bâtiment Mendel, Université Claude Bernard Lyon 1, 44 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne, Cedex, France
Corresponding author: Matthieu Guillemain
Received 26 July 2005, accepted 29 November 2005
Associate Editor: Hannu Pöysa