By Niyati Acharya

Great Blue Herons can be found in marshes, swamps, lakeshores, riversides, beaches, and ponds.  They forage in upland areas and prairies, especially in winter and have a population of 700,000.  They are the largest North American heron, and unlike other bird species, their population is increasing.  Its adaptable traits are reflected in its long thick bill, curvaceous and powerful neck and long legs.

The oldest fossils of the Great Blue Heron are from the Pleistocene Epoch, about 1.8 million years ago.  Various populations changed in size and physical proportions through the millennia in response to differing geographic factors.

The bird stands close to five feet tall, with a wingspan of up to 6.5 feet.  Its large size, blue-gray coloration, and black-striped head distinguish it from other large North American herons.   These herons can be found on any body of water throughout North America and they breed from southern Alaska, across central Canada to Nova Scotia, to parts of the Caribbean and northern Mexico.

One of the Heron’s social signals is called ‘The Sketch.’  From a resting position with all feathers relaxed, the heron smoothly lifts its head and swings the closed bill toward vertical.  During this ascent the lower neck plumes are fully erected, the scapular and occipital plumes relaxed, the torso inclines, and the head twists slightly to one side.  The accompanying vocalization calls attention to the visual effect and makes the display effective even at nightfall.

Unlike some other bird species, Great Blue Herons are adaptable.  They can strike their prey at incredible speed because of a modification of their neck bones.  Their sixth cervical vertebrae enable them to draw their neck into an S shape, and then shoot their heads and bills forward with incredible speed.  They also have long necks and long legs, that allow them to forage in a variety of aquatic environments, and on a variety of prey.  Their bills are adapted for probing, grasping, and spearing prey.  Serrated talons are useful in preening.  They also have few predators.

Over the past century, they have endured habitat loss and disturbance as a result of ongoing
fragmentation along shorelines. A study conducted by the Crested Butte Land Trust determined that human recreation on the Slate River valley adjacent to Crested Butte, Colorado impacted heron nesting. River recreation by boards, kayaks, duckies, and rafts resulted in disturbance behavior more than 9 times out of 10. Their observations indicate that large, loud groups with upright floaters who pause and cluster through the colony section create disturbance to the herons.

Great Blue Herons were hunted for their plumes until the early 20th century, almost to extinction, but are now protected under the Migratory Bird Treaty Act. During the breeding season, they aggregate in large nesting colonies and can be observed at close range. Look for a very loud ‘RAAK’ and other guttural calls.

Sources include: American Bird Conservancy,  Crested Butte Land Trust, Aquarium of the Pacific.org, Sora.unm.edu

Photo credit:  Pearsall, Peter , Gentry, George , Cruz, Andrew , Brima Battle, FWS.org