Migration of wild and captive‐bred Little Bustards Tetrax tetrax: releasing birds from Spain threatens attempts to conserve declining French populations

Oct 25, 2020

Populations of the Little Bustard Tetrax tetrax in the farmlands of Europe have declined greatly over the last century. In Western Europe, France now holds the only remaining migratory population, which currently numbers fewer than 300 displaying males. However, the movements of these birds are virtually unknown, in spite of the important implications of this information for the conservation of this species. We identified migratory movements and overwintering areas of French migratory populations, using wild individuals fitted with satellite or radio‐transmitters. Little Bustards completed their migration journey over a relatively short time period (2–5 days), with nocturnal migration flights of 400–600 km per night. All birds overwintered in Iberia. In addition, we tested the consequences of captive rearing on migratory movements. French wild adults and French captive‐bred juveniles behaved similarly with regard to migration, suggesting that hand‐raising does not alter migratory movements. However, birds originating from eggs collected in Spain and reared in western France did not migrate, suggesting a genetic component to migratory behaviour. These results therefore suggest that a conservation strategy involving the release in France of birds hatched from eggs collected in Spain may imperil the expression of migratory movements of the French population. More generally, to maintain the integrity of native populations, the introduced individuals should mimic their migratory movements and behaviour.

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