Fewer migrant hawks are generally seen in spring in Massachusetts than in fall, in part because their numbers have been reduced by attrition resulting from two long migrations as well as on their wintering grounds. Evidence also suggests that local topography, and spring weather patterns tend to concentrate many spring migrants west of Massachusetts.
Spring hawkwatching is nonetheless rewarding. At many coastal sites, the eye-level views of sharp-shinned hawks, northern harriers, merlins, and American kestrels can be exciting.
The greatest number of hawks moving through our region in spring occurs between mid-April and mid-May, although a few are still moving as late as early June.
Mid-April often hosts substantial numbers of American kestrels, northern harriers, and ospreys in Massachusetts, and some of these species are still moving in early May. During late April and early May sees the passage of broad-winged and sharp-shinned hawks in peak numbers, along with small numbers of peregrine falcons and merlins as well.
Prime Weather Conditions
In spring the passage of a weak low-pressure system from the south is thought to be best, because the accompanying southwest winds and warm air provide lift that hawks traveling on a northeasterly course use to facilitate their migration.
Curiously, coastal sites often afford best viewing on days with moderate to strong northwest winds, and some of the biggest spring flights ever recorded inland in New England have been on days with northwest winds as well.
Clearly, there is still much to be learned about hawk migration, but in general the best rule to follow in spring is to go out on days when the wind is anywhere out of the west. Winds from the east can practically guarantee hawkless skies.
Time of Day
On good days, hawks can be moving as early as sunrise. Inland, one tends not to see as many birds in the early hours as later in the morning, although the birds that are encountered might be closer and afford better views than later in the day when they are often farther away.
Prime time is 8 am to 4 pm (EST), but good numbers—and good birds—can sometimes be seen before or after those hours.
The Parker River National Wildlife Refuge on Plum Island, north of Boston, as well as many sites in the central and western part of the state can all make for good spring hawkwatching. Coastal sites should afford as wide a view to the east, south, and west as possible. Even Cape Cod can provide good hawkwatching, especially area near the narrow “wrist” in the Truro area.