Before the widespread use of herbicides in cereals, the proportion of shot birds which had Polygonum seeds in their crops was just over 30 per cent. It is no surprise that this has fallen to less than 5 per cent on those farms where anti-polygonum sprays have been used systematically. The most important source of Polygona are now the stubbles offspring-sown beans. Simazine does not kill Black Bindweed.
Partridge survival does not, however, seem to have been reduced by the shortage of these autumn weeds. One reason is that a second preferred species, chickweed (Stellaria media) has not declined; another may be that a diet of grain combined with green leaves of the volunteer growth is probably just as nutritious as weeds. There is no evidence of an overall shortage of food, at least until late November, but it has been noticed how grey partridges often congregate on stubbles where Knotgrass is most abundant. It is the distribution, rather than the survival, that is affected by wild food pattern.
Supplementary feeding almost certainly holds the birds better on ground where the wild food has been reduced. Even in October wild grey partridges readily take wheat which has been put out for reared birds, though they are not, of course, nearly so dependent on such food as the released stock.
Later in the season the food situation gradually deteriorates. For example in the third week of November 1973, 222 arable fields on the Game Conservancy's Sussex study area were assessed for the availability of grey partridge food. In many of them food was practically non-existent
However, the 61 Class III fields were still better for jugging than the intensive grass, and partridges did not leave areas with such fields, provided that the ones adjacent had food. In these neighbouring fields winter corn or clover were preferred.
Grain seed in the hay or straw put down for out wintered stock is highly attractive to both species of partridge. Clearly supplementary feeding (discussed later) is often helpful. This type of feeding is much more likely to occur on traditional beef and cereal farms, which are especially favourable to insect survival. It may be that the alleviation of insect shortages, by adopting sympathetic farm systems, would also hold the adults better in hard weather. On the other hand the very high losses in the winter of 1970-71 were not correlated with farming type, the losses being just as high on traditional farms.
A widely held opinion persists that the exceptional winter of 1962-63 caused the lower number of partridges in the early sixties. And at least on keepered areas the low numbers in 1963 could clearly be attributed to the very poor chick survival in the previous summer of 1962.
Winter losses are high in grey partridges - they are much less in wild redlegs -and it is obvious that a reduction in these winter losses-most of which are due to dispersal - would mean that one could tolerate lower chick survival. However, all we do know about winter losses suggests that the rate is very stable. It is no more of a problem - and no less - than it was in the heyday of partridges.
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