Rebhuhn. Schlussbericht 1991–2000 - BAFU

with superior quality reached 0.5% only. In the canton of Schaffhausen, the discrepancy
between the average amount of ecological compensation areas in the whole
canton and the situation in the study sites, where intensive arable agriculture is predominant,
is striking. In the study site «Laconnex» (Geneva) the high percentage of
18.9% ecological compensation areas is partly a result of the fact that three quarters
of the ecological compensation areas are grassland of unsatisfactory quality. These
areas are situated mainly on recultivated soils of former gravel pits with limited soil
qualities. This shows that under the actual basic conditions ecological compensation
areas with superior quality are only established on intensively managed arable land
if farmers are offered intensive consulting and high financial incentives.
The habitat enhancements in the Klettgau were established too late for the grey
partridge. Shortly after the beginning of the project the last individuals disappeared.
In the Champagne genevoise the rapid decrease could be stopped, the remaining
population, however, is isolated and very small.
In 1998 trials to reintroduce grey partridges in the Klettgau were started in the context
of a scientific study. Fist results show that grey partridges intensively use the
newly created wild-flower strips and benefit from the specific habitat enhancement
measures. Similar effects could be shown for several typical breeding bird species
of open farmland.
In the region around «Laconnex» (6.1 km 2 ) in the Champagne genevoise, with its
mild and dry climate, several breeding bird species reacted with a large increase in
population size. The number of common stonechat increased from 11 pairs in 1991
to 49 pairs in 1999. The number of territories of the common whitethroat increased
form 6 in 1991 to 62 in 1999. The number of territories of corn buntings increased
from 2 to a maximum of 36. In the «quail-year» 1997 the density of common quail
was very high, reaching 10 calling cocks per square kilometre. The population trend
is, however, difficult to interpret, because of the invasion-like occurrence of this
species in central Europe. From 1995 onwards melodious warblers nested more frequently
in wild-flower strips (1995 13, 1999 38 territories).
In the study areas Laconnex (Geneva) and Widen (Schaffhausen), where habitat
quality was intensively enhanced, the population trends of corn bunting and common
quail showed similar positive trends from 1991 to 1999. In Laconnex higher
densities were detected than in Widen. Data of the Swiss Ornithological Institute for
the whole country do not show similar positive population trends. In contrast to Laconnex
there was only a weak colonisation with common stonechats and common
whitethroats in Widen. Differences in the population trends can be explained with
differences in habitat structures and different distributions of centres of gravity of
these bird species.
Red-backed shrikes and marsh warblers, two species breeding in field margins and
hedges, did benefit of habitat enhancement with linear structures such as wildflower
strips and hedges and the higher habitat connectivity.
18 Rebhuhn. Schlussbericht 1991–2000