Great Blue Heron

This bird probably comes to mind most when the word “heron” is mentioned. Many people mistakenly call this species a “crane” or “blue crane” but cranes are in a different family and fly with their necks extended rather than tucked in like herons. The great blue heron is the largest of the dark herons, approximately 38 to 53 inches long (as seen in the field) and with a 70-inch wingspread. A great blue heron’s head is largely white (with a thick black stripe over the eye and feathery black crest), the underparts are dark gray, and the back and wings are grayish-blue. The legs are dark.

In spring, the great blue heron is a common migrant from mid-March to late May; in summer, a breeding resident across nearly all of Pennsylvania with the exception of areas along the Appalachian Plateaus Province, possibly because of polluted rivers and streams in the region as a result of coal mine operations and acid precipitation. The species generally breeds across the northern United States, through much of Canada to Alaska and south to northern South America. 

Fall migration is gradual and not well defined as heron numbers seem to thin with fall and dwindle by the onset of winter. Some remain as winter residents, hanging out along waterways and other open water until the water is iced over or fish populations are depleted in smaller waterways. The species winters principally along the Atlantic coast, the southern states and Central and South America.

Great blue herons inhabit saltwater or freshwater areas near trees suitable for nesting. They often nest in remote and inaccessible places. They may travel far (more than 10 miles in some cases) to forage, and sometimes choose foraging sites close to human activity, such as urban waterways or the marshy drain-field adjacent to a shopping mall. Great blue herons can nest either singly or in colonies, but usually in colonies and sometimes among the nests of other herons. Multiple nests may be found in the same tree. The nest is a platform of large sticks lined with fine twigs and leaves and built in a sturdy crotch or on a limb. Herons occasionally nest on the ground, on a bush or on a human structure. The outside diameter of a nest can be anywhere from 20 inches to up to four feet across; a larger nest is the result of the nest being refurbished from year to year. The male brings nesting material to the female, which does most of the actual building. Colonies sometimes persist for several years or decades, then disappear for unknown reasons (perhaps due to changed food availability).

Great blue herons are secure in Pennsylvania, and the Pennsylvania Biological Survey recommends management attention due to their colonial nesting behavior. They also serve as an indicator for high-quality habitats.