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Vocal stability in two separated populations of a non-oscine bird: the Eurasian woodcock Scolopax rusticola [abstract]

Aubin, T, Mathevon, N , Gonçalves, D & Ferrand, Y (2012). Vocal stability in two separated populations of a non-oscine bird: the Eurasian woodcock Scolopax rusticola [abstract]. Bioacoustics, Volume 21 (1): 26 -27



Variation in vocal features of populations belonging to the same species has mostly been investigated in birds that learn their vocalizations, the oscines, where vocal character shift is driven by genetic as well as cultural transmission. More investigations are thus clearly needed to understand how acoustic signals can evolve in non-learning birds. In the Woodcock, a non-oscine, males perform conspicuous display flights, a behaviour known as “roding”, over the woodland canopy at dusk, as they search for females. During these courtships, the birds emit roding calls, consisting of 2-5 low-frequency croaks followed by a high-frequency whistle. Although this migratory wader is widely distributed in the Palearctic Region, from Western Europe to Japan, some sedentary populations exist in isolated islands such as the Azores archipelago. The aim of the study was to compare the possible acoustic divergences existing between two separated populations: a migratory one breeding in the centre of France and a sedentary one living in Azores archipelago. Thus, we have recorded the roding calls of the migratory population (30 individuals) in two close localities (Compiègne and Rambouillet) and of the sedentary population (36 individuals) in two islands (Sao Miguel and Pico islands). On the basis of DFAs calculated for temporal and frequency parameters, it was impossible to correctly classify the calls according to their population origin, indicating that the roding call has not diverged between the two separated populations. Contrary to the findings obtained in recent studies with other non-oscines in similar situations, it appears that the acoustic features of this wader have remained remarkably stable upon a long period of time. This result is discussed in regard to the habitat-dependent selection hypothesis, the duration of the reproductive isolation of the Azores population and the existence of a possible introgression of external gene flows in this isolated population.