Changes in reproductive habitat of gray partridge after burning

Abstract

We investigated the effects of winter controlled burning on the breeding habitat of the Pyrenean gray partridge (Perdix perdix hispaniensis Reich.). Floristic composition and vegetation structure were sampled on 198 sites, including 64 recently used by hens for nesting or rearing of broods, 90 within partridge habitat burned under dry conditions, and 44 burned under wet conditions. During the early breeding season, birds selected shrublands of broom (Cytisus purgans (L.) Boiss.) with an average canopy coverage of 60% and an average height of 0.50 m. Birds avoided sites where shrub cover was more than 80% or less than 20%. The most critical effect of burning on gray partridge brood habitat was the reduction of the cover in the 2 vegetation layers providing protection against predators (0.05-0.25 m, and 0.25-0.50 m). In the case of "dry burning", the recovery of suitable habitat took more than 8 years for nesting hens and flightless chicks, but only 5-6 years for broods older than 3 weeks. Data obtained by radio-tracking eight broods indicated that "wet burns" (mean size = 4 ha) were better than "dry burns" (mean size = 15 ha) for maintaining good brood habitat. For the "dry burns", we recommend that burned patches be equal to or less than 5 ha and separated by unburned patches of 10-15 ha. In both cases, the frequency of fires should not exceed once every 15-20 years.