Back in the 1960s when research started on the potential environmental impacts of the various 'wonder chemicals' there was sceptiscm and even anger at the idea - it was anti farming, it was communists and so on. Remember the book Silent Spring and the backlash against the author? The Game Conservancy for its part was looking at the impacts on grey partridge, that came in the 1970s I think. Now we take it as fact there is an impact on grey partridge chick survival rates from herbicides and insecticide use. All the research on nesting cover, stubbles, the innovations of beetle banks and so on, all thanks to Game Conservancy research and now embedded in agri-environmental schemes. Lots of things help and hinder grey partridge. Lead shot is on the hinder side and the GWCT has reviewed that evidence. I agree there are bigger impacts on grey partridge. But that's not to say lead shot should be ignored. Every wild bird counts.
As regards sparrowhawks, an intensive study of sparrowhawk and buzzard diet in the breeding season in England found the remains of a grey partridge only once in 73 prey items from five buzzard nests and 295 prey items from five sparrowhawk nests. GWCT did some research also and computer modelling of all data suggested that, at low densities, losses to raptors would result in a 39% reduction in average spring pair density over the long term. Because shooting losses occurred before the peak time for losses to raptors, the two causes of loss were largely additive. Shooting alone at 40% resulted in a 23% reduction over the long term in spring stocks, and shooting and raptors combined reduced spring stocks by 52%. Crucially, the impact of raptor predation was greatest at low partridge density; above approximately five pairs per 100 hectares the impact was much less