I also hunt in NY.I would look in your hunting regulations that they give you when you buy your license.They have a list of Environmental Conservation Officersfor every deer management unit,DMU.
Call theEnvironmental Conservation Officerthat's closest to your hunting area.They have to check out every complaint.
They also have a number to call 1-800-TIPP-DEC,to turn in poachers or any violater.You can report violations 24 hours per day.Give them as much information that you can on the poacher.His license plate number,where he hunts,when is the best time to catch him poaching,ect: