The entire "scientific explanations" section is bs.
What is a "scientific explanation" of a folk belief. 
You may easily list any number of luminescent phenomena which may have helped inspire this folk belief, 
but by doing so, you are listing luminescent phenomena, you are not discussing the folk belief in question.
This article is not called "list of possible natural light sources in swamps", it is supposed to discuss a widespread folk belief.
The academic discipline responsible for this is folklore studies, not the pseudo-scientific nonsense about owl plumage and swamp gas.  (𒁳)