The main idea of the paragraph would be the penguins camouflage and feathers help them in their survival
3 supporting facts would be: it makes them hard to see in the ocean for predators, they blend with they sky, their feathers protects them while swimming and keeps them warm.
(this could be worded better but yeah, hope I could help!)
The inclusion of reputable sources and specific facts would best strengthen the author's main argument because it would offer factual proof instead of just the author's opinion on the matter.