Hi Tony,
the Teign is a fairly small estuary, but does get some nice birds; locations such as Flow Point, and Passage House Inn are worth looking at. [Not waterbirds, but to be mentioned; Just down the coast road from Shaldon is Labrador Bay, with the easiest Cirls you ever will see - often without getting out of the car.] Up river at Newton Abbot is Jetty Marsh.
Wandering up the coast a little way, you have the Exe estuary, deservedly famous. Dawlish Warren is the closest and obvious start point. Following up one side and down the other are various viewpoints and locations and indeed reserves - Exminster marshes, Matford marsh, Bowling Green Marsh, and Exmouth Imperial car park are just a few.
I'd get busy with the search engine of your choice and look up a few of the local patchers' twitter feeds [teign birds is one] to get latest gen, and the RSPB's and DW's sites for location maps etc.
Have a great time, mate!