The food availability of reared grey partridge chicks was experimentally altered to test whether the consumption of invertebrates identified in the literature as intermediate hosts of parasitic worms caused increased parasitic infection in partridges. However, only 14 (17%) of the autopsied birds had levels of parasites that were thought likely to have caused death. The post-mortem examinations of 79 birds showed that 33 of these contained nematode or cestode parasitic worms.
The survival of chicks in a brood was, on average, inversely related to the percentage of ants in the diet (Figure 2).This may reflect increased disease susceptibility or perhaps a poorer diet.įigure 2: Relationship between the percentage of ants in diet and chick survival for three sites in Norfolk, 2001-2003 Ants, as well as several other invertebrates eaten by chicks at all sites, are known to be intermediate hosts of internal parasitic worms. However, we found that the chicks consumed more ants than usual. Analysis of faeces revealed that chick diet contained a range of insects that was typical of earlier studies (Figure 1).įigure 1: The mean composition of grey partridge brood diet at three sites in Norfolk, 2001-2003 Breeding success for the radio-tagged birds was low, 54 females laid clutches but only 34 actually hatched young and only 20 broods survived longer than six weeks. We also did post-mortem examinations on all partridges found dead or in poor condition.Īmong the radio-tagged birds, seven were killed by predators, six died as a result of disease and a further 11 died from a variety of other or unknown causes. We followed these birds through the breeding season and assessed their breeding success, survival and diet. We caught 85 female grey partridges and fitted them with radio transmitters at three study sites in Norfolk with a history of high unexplained losses. To establish whether diet and disease susceptibility had altered in recent years, we did a three-year study of wild grey partridges in East Anglia. Consequently it was suggested that chick-food availability had become so low that grey partridge chicks were being forced to eat some insects that harboured internal parasites and spread disease. Although the precise causes for this reduced breeding success are unknown, it coincided with increased reports of parasitic disease in wild birds. In the mid and late 1990s, a number of estates in East Anglia suffered successive years of poor breeding and their partridge stocks went into decline.
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