Twenty years of the grey partridge population in the LAJTA Project (Western Hungary)

Abstract

The Lajta Project covers 3,065 ha. Within this area crop cultivation is dominant. Fields are separated from each other by forest belts and tree rows, extending altogether over roughly 120 ha. This habitat structure characterized by cultivation of 12–15 field crops sustained partridge population with densities of 1.75 birds/km2 (1991). The Project started in 1991/1992 and aimed to increase the carrying capacity for grey partridge and other small game species living in the area. A full–time gamekeeper was employed and habitat improvements were initiated. Four years later, the breeding population increased to 10.1 birds/km². Besides increased numbers of nesting pairs, the number of reared chicks also increased, from 5.1–11.2 individuals/km² in 1990 to 27.3–38.4 individuals/km² in 1994. However, field sizes did not change significantly. Although the lengths of field margins increased by approximately 25 % (from 82 m/ha to 115 m/ha) under the influence of habitat management, they still reached only half those found in the countries of Central Europe where private ownership of land properties is dominant. After the privatisation of fields in 1995 as part of the political change in Hungary —affecting approximately 50 % of the project area— the possibilities of habitat improvement decreased, and the technological pressure on large–scale farming area increased. Following these processes the grey partridge population again decreased to 1.43 birds/km² in 1997. As a result of the new management strategy applied in the project since 1996 we observed a slow increase in the breeding population, which stabilized at around 5 birds/km2, between 2007 and 2009. The August density increased in the same period from 4.5 birds/km² to 13–17 birds/km². During the two decades in which this research was conducted, chick mortality and winter mortality were extremely high. The key factors influencing grey partridge population dynamics in our study area seem to be clutch and chick losses and winter mortality. To determine the relationship between environmental factors and the grey partridge population parameters, principal component analysis (PCA) was used. August grey partridge density was positively associated with ecotone density and bags of red fox and avian predators (magpie and hooded crow). The density of grey partridge in spring and August also correlated with feral dog bag and feral cat bag. Habitat parameters showed a positive correlation with the density of grey partridge both in spring and in August. The levels of abundance of feral dog and feral cat populations also correlated negatively with winter losses.