I lost 14 of my pigeons in two days. I am new at this and expected losses, but now I really feel terrible. I have a few left and have opened the coop and let them have free range. They come and go as they please and I have thrown out all feed and bought new just in case it was tainted. Water was fine and protectd from droppings and the like. Perhaps they were sick when I got them, and I really cannot detail any symptoms other than death that they exhibeted. Bummer really, but hopefully my next batch will be better. The survivors I am doting on as best I can. The ones that survived are huge, and look like partridge. I wonder if the big ones killed the little ones.
I walked out to my loft yesterday and my grizzel hen was dead on her perch.
With free range the hawks will soon reduce your numbers to zero.
It is possible that some of the pigeons were infected with one or more diseases when you got them, especially if you got them from more than one source. What types of breeds did you have? Meat pigeons (Giant Runts, White Kings, Pouters, Maltze, Giant Homer, etc) can kill smaller pigeons, Racing Homers can kill smaller pigeons (tumblers, owls, swallows, nuns, rollers, etc).
Pigeons fight for social order just like chickens do. It can get violent to to point of having a bird scalped or killed. It is best to keep like breed birds with birds of that size class at the very least, don't mix tumblers and homers for instance.
Now that all of the birds have been exposed to what ever it was, the couriers have survived and those new exposed are mostly dead. Disease and death exposure can go both ways when mixing pigeons. When getting new birds, sometimes the introduction into a new loft will stress the birds to the point of succombing to the disease they carried as well as the other birds. You need to have a small loft (a rabbit hutch works) to quarentine new birds for 3 weeks before mixing with existing stock.
In the mean time, feed Sulmet in the drinking water or take a small eye-dropper and squirt a small amount directly down each birds throat.