Smelly Water Barrel... mystery solved

Thanks to an avid CBC listener the answer to the smelly water barrel question from last week is solved:

Shelagh writes:
In response to the question about the horrid smell in the rain barrel, I
suggest that the problem is pigeons. While in Calgary I had the same issue,
year after year. No matter how often I cleaned the barrel, it stank. One
spring, just after one of the famous Calgary downpours, I noticed egg shells
and baby bird bits in the rain barrel and it all came together. I had had
pigeons roosting on the roof that drained into the barrel for years - could
not get rid of them. So, I think the caller's problem probably stems from
pigeon guano and pigeon nest refuse. It's nasty stuff and the water should
not be used any where near food crops. Pigeons carry quite a few diseases
that are transmittable to humans.