This story from Gold Key Comics’ UFO FLYING SAUCERS #3 from 1972 posits the idea that some UFOs may be living creatures in the sky… and presents several classic evidentiary stories –
• The Crawfordsville, Indiana Monster
• The Philadelphia Purple Disc
• The Florida Honeycomb
It suggests several related phenomena, such as mass bird casualties, perhaps from venomous aerial predators.
Some great past evidence presented in an easy to read form for your enjoyment!