The New York portion of Deer Pond Farm opens this weekend.   10 miles of trails and 447 acres of public use have been added to a preserve in Sherman.  The Connecticut Audubon is celebrating the opening with a series of activities tomorrow.  The Pawling section is a sloping half-mile walk from the parking area at 57 Wakeman Hill Road in Sherman.  Parking and access to the New York and Connecticut trails are from this address.  The events include a guided bird walk at 8am, a birding demonstration at 9am.  A ribbon cutting and brief ceremony will follow at 10.  A birds of prey demonstration will be held at 10:30am.  Opening day programs and guided hikes are free but online RSVPs are requested.