Common Grackle

The Common Grackle is one of the most abundant birds in North America, with a population estimated at almost 70 million. Along with other blackbirds, they are well-known for forming large communal roosts during the non-breeding season. Here in New Hampshire these roosts are largest in October and November, when they may host over 100,000 birds (although 3000 is a more typical high count). Roosts can form in a variety of habitats, including forests, swamps, and other wetlands, and the best time to observe the birds is at dusk or dawn when they are arriving or leaving. Seeing one of these “rivers of blackbirds” is a special treat both in early spring and late fall. Roosts are even larger in the winter in the southeastern U.S., where they can contain over a million birds.

The Common Grackle’s gregariousness has not made it popular with agricultural interests, since large flocks of blackbirds can cause extensive damage to crops. In addition, roosts in urban areas are messy, noisy, and potentially a source of disease. As a result, grackles are viewed as pests in some areas and subject to a variety of control measures, including hazing, spraying crops to make them distasteful, or – in some cases – killing the birds themselves. Grackle populations have declined by about 50% across most of eastern North America over the last half-century, and while it’s easy to finger blackbird control as one of the causes of this decline we honestly lack the data to be sure.

It’s never easy to reconcile our own economic interests with bird conservation, and the conflict between blackbirds and agriculture is a case in point. Since the species is still extremely abundant, is it justifiable to curtail control efforts and risk higher crop losses? Or should we strive for solutions that balance both interests and allow grackles some breathing room while acknowledging that they’ll not likely return to their pre-decline numbers? Either way, coming up with workable solutions to such issues is ultimately both an art and a science.

There is also concern about threats like habitat loss, climate change, and the effects of pesticides on the aquatic insects which comprise an important part of grackle diets during the breeding season. Other species that share grackles’ habitat, including Eastern Kingbirds and Yellow Warblers, are also showing poorly-understood declines, so there’s always more to the puzzle than meets the eye.