Summary1. Bird populations can be eciently managed only if the demographic mechanisms that cause change are correctly understood. Here we illustrate the demographic variables causing decline among grey partridge Perdix perdix populations in France by comparing populations that show contrasting trends. The analysis combined a ®eld survey at 10 contrasting sites during 3 years, modelling and statistical analyses; survival rates and reproductive success were estimated through the largest-ever radio-tracking study of hens, while density was estimated through counts. 2. Population viability analyses showed that, in France, north-western populations of grey partridge were healthy whereas south-eastern populations were declining. 3. Elasticity analyses accounting for environmental stochasticity indicated that the survival rate during shooting, over winter and at the time of the ®rst nesting attempt were the most important demographic in¯uences on population growth rate. The hatching rate, covey size at hatching of ®rst clutches and chick survival rate were secondary. The contribution of replacement clutches to population change was low. 4. Multiple regression showed that hen survival during the ®rst nesting attempt explained 33% of the variability in the population growth rate across populations. The shooting pressure increased with the health of the population. 5. Improving survival rate during winter and the ®rst nesting attempt was not sucient for recovery in a declining population. It was also necessary to increase simultaneously the hatching rate of ®rst clutches and chick survival rate to produce a stable population that could sustain shooting. 6. Low hen survival rates, in particular during the breeding period, explain the recent decline of grey partridge populations in some regions of France. However, the recovery of populations will need a simultaneous improvement of several demographic parameters.

Summary 1.The grey partridge is a species of conservation concern, in common with many farmland birds. Its widespread decline in western Europe has been attributed to agricultural intensification. Attempts to restore populations have concentrated upon habitat management. In France, a mosaic of strips planted with maize-or kale-based mixtures is widely used to benefit the grey partridge on intensively cultivated farmlands. The rationale for planting these summer-to-winter cover strips is to increase the overwinter survival rate and hence breeding density. Although this policy is costly to apply, there is little information on its effectiveness. 2. We tested effectiveness of this management scheme as a practical way of improving or restoring partridge populations. We present data from a 6-year before-after controlimpact (BACI) experiment replicated across four study sites. We monitored partridge populations to estimate breeding density, reproductive success and overwinter mortality. 3. During the course of the study, no partridge population increase occurred on managed areas compared with control areas. Wildlife cover strips did not improve reproductive success but were associated with higher overwinter 'apparent mortality' rates. 4. Some field data suggested that there was a predation risk at cover strip-field edges. Cover strips may concentrate a number of species within small isolated areas and may act, under some circumstances, as an ecological trap for prey species such as the grey partridge. Due to these complex and unforeseen interactions, this habitat management measure proved unsuitable for partridge restoration. Synthesis and applications. This study has demonstrated the necessity of field experiments at a farm-scale to test the effectiveness of habitat management schemes. A priori assumptions based on smaller scale studies, even if they are supported by some field evidence, can be misleading because they fail to capture the emergent properties of larger scale systems. This study is a specific illustration of how the BACI approach is a powerful tool for addressing wildlife management problems at large spatial scales.

We studied Grey Partridge Perdix perdix mortality during breeding to identify the environmental causes of a long-term decline in adult survival. We radiotagged and monitored daily from mid-March to mid-September 1009 females on ten contrasting study sites in 1995-97. Simultaneously, we recorded habitat features and estimated the abundance of Hen and Marsh Harriers Circus cyaneus and C. aeruginosus, Red Fox Vulpes vulpes and mustelids. We experimentally tested whether scavenging could have biased predation rates. We also examined, through the necropsy of 80 carcasses of Grey Partridge, whether disease, parasites or poisoning could have been ultimate causes of high predation rates. The survival rate of radiotagged females during spring and summer ranged from 0.25 to 0.65 across study areas. Mortality peaked in May, June and July when females were laying and incubating. The direct negative impact of farming practices was low (6%). Predation was the main proximate cause of female mortality during breeding (73%) and determined the survival rate, suggesting no compensation by other causes of mortality. Ground carnivores were responsible for 64% of predation cases, and raptors for 29%, but this proportion varied across study sites. Disease and poisoning did not appear to favour predation, and scavenging was not likely to have substantially overestimated predation rates. The predation rate on breeding females was positively correlated with the abundance of Hen and Marsh Harriers, suggesting an additional mortality in areas where harriers were abundant. The proportion of raptor predation was linearly related to harrier abundance. The predation rate was not correlated with the abundance of the Red Fox and mustelids. A potential density-dependent effect on the predation rate was confounded by the abundance of harriers. We found no convincing relationship between the predation rate and habitat features, but we observed a positive relationship between the abundance of Hen and Marsh Harriers and the mean field size. This suggested that habitat characteristics may contribute to high predation rates through predator abundance or habitat-dependent predation.

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Fifty-one European hares Lepus europaeus Pallas, 1778 were monitored during at least one month by radiotracking in an intensively farmed landscape. The mean home range size of 21 hares monitored during at least six months was about 100 ha. During summer and autumn, seasonal home range size and the mean distance between fixes did not reveal any difference in the use of space between sexes or between age classes. However, according to the shifts of monthly resting range centres, females seemed to be more sedentary than males. The night-time activity range was often larger than the daytime resting range and partly or totally overlapped it although resting and activity locations were rarely the same. Hare movements did not show any important changes in response to crop harvesting or shooting.Office National de la Chasse, Saint Benoist, 78610 Auffargis, France