We have a colony of Little Swifts nesting under the eve's of our roof, there are literally hundreds of them. They seem to decrease in the winter months as some move away and some remain.
The thing that has us stumped is why we find so many young falling out of the nests. There are the tiny pink helpless ones right up to the almost fully grown adult looking birds. We have managed to raise one ! so far !!
Everything I have read does not mention any form of cainism? My only other thought is that the parasite load gets to much and they vacate the nest to try and get away from mites etc??