Behavioural evidence of hybridization (Japanese × European) in domestic quail released as game birds

The European quail is a partial migrant bird considered 'vulnerable' by the European community. The decline of this subspecies has spurred an annual release of large numbers of domestic Japanese quail. Prezygotic and postzygotic isolating mechanisms have not been established between these two subspecies, enhancing the risk of hybridization. In addition, anecdotal reports suggest that hybridization is commonly practiced in game farms of domestic quails. In this article, we present the results of behavioural characterization of the quails produced by two European game farms: one French and one Italian. First, we looked for evidences of hybridization in both game farms. Using actographic methods, we measured migratory tendency. Birds, hatched in summer, were submitted in autumn to an artificial increase of daylength (LD 14:10) for 60 days. In quails, the length of the cloacal vent which is a good indicator of sexual development, was monitored every 10 days. We noted the appearance of cloacal foam in males and egg-laying activity in females. In addition, mating calls produced by the males when sexually mature were recorded and analyzed using spectrographic methods. Seventeen males of 27 from the French game farm exhibited nocturnal restlessness. Most of the birds of the Italian game farm (40/44) developed sexually without showing any migratory activity. Since Japanese quail has lost its migratory impulse during the domestication process, the presence of migratory activity in quails of both game farms clearly demonstrated the introduction of wild European quail. Spectrographic analysis of male mating calls confirmed this assumption: some males in both game farms (21/27 in the French game farm, 5/22 in the Italian game farm) produced calls similar to those produced by control lines of hybrid quails (Japanese × European). In an additional experiment, we report the results of encounters between males of the French game farm and males of European quail. One bird of each strain were put together on day 1 and on day 3, we introduced in the pen a female European quail. In 11 cases out of 11, the male of the French game farm dominated the male European quail and monopolized the female. These results imply that releasing hybrid and Japanese quails in the wild could rapidly lead to widespread genetic pollution of the western Palaearctic populations of the European quail.