My gut feel is the local market is being saturated with new build to rent duplexes.

PS is it over saturated?

The market is saturated with vacation rentals in the desert area.

Sorry hit post there- I think second homeowners in a broadly good market as we are in (not speaking on your micro market which may be different) may not be as motivated as some other categories of sellers (foreclosure, eviction landlords, bankruptcy, etc) so may not have high response rates but that said may not be a saturated market with a bunch of other investors.

Now they are maintaining saturation levels.

Best - Heidi we been poking around the Madison area there is no question that many of the mid west markets mid south and deep south have been over saturated by out of state investors the key now is to find places before the hords OR the turn key operators and their marketing companies find them. .. 

The absentee and pre foreclosed list I have gotten from Listsource and Propstream seem to be heavily saturated.

Then it became saturated, and the market got even tighter.  

Is the area becoming over saturated with STRs?

It isn't just the amount of rain, but how long the rain lasts and if the ground is already saturated (or frozen) and can't hold any more water.