Demographic parameters of reintroduced grey partridges in central Italy and the effect of weather

Grey partridge populations declined in Europe from mid-1950s onwards mostly due to modifications of agricultural cropping. In Italy, the decline was even more dramatic because of over-hunting and restocking with allochthonous birds. We carried out a research on a re-introduced population in Central Italy from 1995 to 2005, with the aim of evaluating the reintroduction success and separating the intrinsic and external factors influencing year-to-year changes in partridge density with particular respect to the weather. Average spring density was 4.5 pairs per square kilometre (SD = 1.52); our population reached a peak few years after the reintroduction and then declined. Brood production rate was close to that of declining European populations (average 33.9%; SD = 10.21), and chick survival rate (average 40%; SD = 17.61) determined the change of breeding abundance from year t to year t + 1. Our population seemed to be mainly affected by brood production and chick survival rates and by the weather; in particular, higher early winter and spring temperatures increased breeding density whilst higher early summer temperatures decreased brood production rate.