David....a few more locations to add to Kayaker's northern Mass suggestions; Salisbury State Reserve (SSR), Plum Is. (PI) as a whole (Parker River Refuge is located on the southern end)....although great bird offerings, they also offer great sea and marshscapes. Mosely SP, just over the bridge beyond Deer Is. It's small, but is still on the Merrimack and offers some nice trails and scenics as well as bird photo ops.

These are all easily accessible day trips from Portsmouth, but be prepared to pay admission fees to SSR (depending when you go), Maudsley and PRNWR.