Site Summary: Site Summary: Mystic River Watershed

Map of the Mystic River Watershed IBA site

Nominated By:

Marj Rines



Towns and Counties:

Boston, Medford, Somerville; Middlesex, Suffolk



Major Habitats:

lake/pond, river/stream, urban/suburban

Land Use:

hunting/fishing, other recreation or tourism

Site Description:

Each spring, starting in mid-May and running through the end of June, there is an impressive run of Alewives and Blueback Herring up the Mystic River and into the Lower Mystic Lake. This creates a tremendous food source for gulls, cormorants, and, most impressively, Black-crowned Night-Herons.

Current Conservation Status:

The herring run appears to be a very important food source for a significant portion of the breeding Black-crowned Night-Herons in the state. The river itself is obviously extremely important to maintain the herring.

Ornithological Significance:

All the numbers listed below are exact counts taken from a single location at the north end of Lower Mystic Lake. Many, if not most, herons are roosting in trees and are extremely difficult to see, so these numbers represent a definite undercount of the birds on Lower Mystic Lake. In addition, I have heard anecdotal information from acquaintances that many sections of the Mystic River also have large concentrations of herons. The ideal time to count birds is just before sunrise. The high count in 1993 is the only one that was taken before sunrise.

Other Important Species:



Maximum Numbers


Black-crowned Night Heron B 197 1993
Black-crowned Night Heron B 120 1994
Black-crowned Night Heron B 126 1995
Black-crowned Night B 103 1997

Data Sources:

Marjorie Rines, personal observations

Download the Map:

mystic-iba.jpg 1.02 MB