Alan Archer was one of three young men who - back in 1953 - sparked the genesis of an idea to make RSPB Old Moor what it is today.
It was upon reading of a theory by writer Ralph Chislett that said waders - birds commonly found along shorelines and mudflats - were passing through the Dearne Valley - that Alan and friends Colin Bower and Terence Kilburn decided to see for themselves.
The plaque was placed there as a result of their tireless work.
Alan, now 84 and living in Hoylandswaine, still visits the site.
He added: “Back in those days three of us lived in Worsbrough Dale and were bird watchers.
“It’s very popular for bird watchers and families, and has been very successful.
“In a way I am proud of the fact that so many people are getting enjoyment out of our efforts in the early days.”
Harry Wood, current visitor operations manager at Old Moor, added: “Back in the 1950s, 60s and right up to the 90s the area was one of the most ecologically deprived parts of Europe - it was a really bleak place.
“They started logging their findings of what they saw here, which essentially was the genesis of getting protection of the site.”