The Majestic Great Blue Herons

These beautiful, amazing birds are thriving in the Chesapeake Bay region
Writer: Joseph Casey Martin
Photographer: Vickie Kite Milburn

Soaring above the lush estuary of the Chesapeake Bay, the great blue heron is one of Southern Maryland’s most iconic and graceful embodiments of nature.

Boasting a grand wingspan of 6 feet and average height of 4 feet, it is the largest species of heron in North America. Great blues are named after their appearance, which is usually a lighter to darker grayish-blue with elongated light-
orange bills and black crowns. In flight, they curl their necks into an S shape. They feed primarily on fish, frogs, insects, other birds and small mammals by spearing their prey with their long beaks.
In Maryland, they inhabit and forage for food in a variety of environments — tidal wetlands, stream valley wetlands, lake and pond shorelines, and inland fields along the Chesapeake Bay and on the Delmarva peninsula, says Dave Brinker, the Maryland Department of Natural Resources’ technical expert on colonial nesting waterbirds for the past 30 years.
 
Nest Building
“In Southern Maryland, great blue herons locate their breeding colonies in mature forests of hardwoods and loblolly pine,” he says. These colonies can grow to be massive.
Sandy Spencer, a biologist for the Patuxent Research Refuge, a nearly 13,000-acre U.S. Fish and Wildlife Service National Wildlife Refuge on the Patuxent River near Laurel, says the herons nest in large colonies, sometimes in the hundreds.

“The nests are ‘platforms’ made of sticks woven together about the size of passenger vehicle tires. Eventually over the years, if the nests are densely placed together, the shading from the nests over the tree’s leaves and the guano damages the trees,” Spencer says. The nests then begin to die and become unstable, and the colony has to shift or relocate.
The colonies themselves can be decades old and can be “challenging to locate,” Brinker says. For that reason, there might have been a small number of colonies that were missed during a 2013 survey, he says.


 
The great blue heron is thriving.
“The great blue heron population in Maryland is healthy and growing,” Brinker says. “Back in the late 1980s, the breeding population of the great blue heron in Maryland was estimated to be about 3,750 breeding pairs. The breeding population has grown strongly from that to probably over 7,500 breeding pairs today.”
The numbers are doing so well that regular monitoring of the herons has been reduced in order to focus on other species of birds that might be in decline.
Locally, great blues are most likely still concentrated in Charles and St. Mary’s counties, says Brinker, referring to the 2013 study.
“When surveyed in 2013 there were 75 pairs breeding in Calvert County, 315 pairs in Charles County, and 1,250 pairs breeding in St. Mary’s County,” he says. “At that time, the largest colony was in St. Mary’s County, and it supported 780 breeding pairs.”
These breeding pairs were spread out between seven colonies in Calvert and 14 each in Charles and St. Mary’s.
A couple of factors for this sustained growth would be an abundance of sustenance and a lack of direct predators. However, one notable predator of great blues is the great horned owl. DNR’s Spencer says those owls are the “top predators on the chicks, so sometimes the [nesting] site doesn’t work out.”
Thanks to conservation efforts and scientific research, Marylanders will be able to enjoy the sight of great blue herons for years to come. Of all of the beautiful and diversified species in Southern Maryland, the great blue heron stands out as one of most amazing. •