Red-legged Alectoris rufa and rock A. graeca partridges hybridise at a contact zone. Hybrids are viable and fertile. Rally calls (implicated in species isolation mechanisms) have been studied in males of the two species and in F1 hybrids. 3 temporal (call duration, silence duration and sound/silence ratio) and 3 frequency parameters (fundamental frequency, frequency of the maximum amplitude and frequency band containing 80% of energy) were used in a Principal Component Analysis. This indicated a greater variability in rock partridges than in red-legged partridges. Two frequency parameters (frequency of the maximum amplitude and frequency band containing 80% of energy) appear to be the factors differing most between the two species. In order to understand the decoding system of the two species, broadcast experiments were made on males. Each species was tested with natural conspecific and heterospecilic rally calls. The responses in terms of latency, duration and number of calls to conspecific and heterospecific signals of males of the two species did not differ significantly. Although signal coding exhibits several differences, the decoding system seems to be broader, allowing interspecific recognition.
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