Because of where we live we can go to the nesting site in Rondeau and see a Prothonotary just about everyday.
We are really not the blase about the bird and there is a story behind the expression.
When we were in Virginia prothonotarys were common.
One of the people we were birding with said, "Oh, it's just another prothonotary. I wish I could see a yellow warbler."
In Virginia prothons are common and yellows are rare, the reverse of our situation.
Geography is everything.
For Prothonotary Warblers it pays to be bright. Males that are brighter yellow gain access to better nest sites than less colorful males, according to a study conducted in Louisiana.
source - Cornell Lab of Ornithology.