pigeon dying

I have a few pigeons. They were all nice and healthy. But recently this winter I noticed one pigeon is not eating and standing still. He was not active at all. I dont have enough knowledge about pigeon diseases but I tried my best. He had sounds of breathing in his nose. As his time was ending...

Hey guys, well first my pigeons started to die from the harsh weathers here. Now that thats been taken care of, i have new a new problem. 4 of my pigeons died in 2 days. (7 pigeons died in a week, weather/disease problems). Well the 4 that died in these last 2 days is not due to weather...