ECOLOGY OF PARTRIDGE .2. ROLE OF PRE-HATCHING INFLUENCES

In wild populations of the partridge (Perdix perdix) in south England, pre-hatching factors, sex ratio, clutch size and percentage hatch, are not correlated with each other or, with the exception of the sex ratio, with chick survival which is the ''key factor'' (Blank et al. 1967). Data from the artificial incubation of 26,416 eggs collected over 4 years from 14 beats on an estate in south England showed that there was a tendency for some beats to have a higher percentage fertility than others. This was inversely related to the area of fallow in early spring and the average size of the fields. Chick survival in captivity varies over the 4 years from 60% to 86% and was correlated with the percentage hatching. It is considered that these observations on eggs and chicks reared in captivity have shown that many of the pre-hatching factors recognized by Jenkins et al. (1963, 1967) in the red grouse also occur in the partridge; but their influence on the breeding success of protected populations in southern England is normally masked by the heavy chick mortality due to other immediate factors.