Harvest probabilities of European ducks: the very first estimation based on reward rings

Abstract

Ringing-recoveries are an overarching element of population dynamic studies that allow estimating mortality causes and hence improve wildlife management. However, possible drawbacks of recovered rings reside in the fact that reporting probability is rarely known, but consistently lower than 100%. Thus, estimating harvest probabilities (mortality probability due to harvesting) of exploited species without knowledge of ring reporting probability by people exploiting these animals is not straightforward. We here provide the first ever reward-ring study carried out to evaluate European reporting probabilities, hence European harvest probabilities, in three species of ducks (Mallard Anas platyrhynchos, Eurasian Teal A. crecca and Common Pochard Aythya ferina). The 70 Euros reward on some rings was considered to yield a total return of the rings, allowing by comparison to evaluate the reporting probability of standard rings. After the initial year of ringing, annual reporting probability was very similar among the three species, at 0.63-0.66, suggesting two-thirds of the found rings are sent back to the ringing centre. This allowed computation of the annual harvest probability, which was up to 0.27 during the first months after ringing in fall but decreased to 0.04-0.10 during later years. Compared to North American results, the present estimates suggest birds are submitted to a heavy hunting mortality during the first months after ringing, but this pressure declines in later years, likely owing to counter selection of vulnerable/exposed individuals and/or learning by the birds.