a pal of mine done sliding covers for his stock birds , plastic channeling from b&q ,with triplex roofing sheets cut to size .cheap and simple enough .
I have had both a hen and a cock be "single sitters" a few years apart ,not related , and both done a great job . noted for both (it was the first nest)
how do you dispose of your pigeons droppings ? I bag ours up and they go in the dustbin , the shopping bags will be 5 p each from October ? I might have to start stock piling them now