The Glorious Great Blue Herons of Maryland

Conservation

Surveys

Recently, the Maryland Department of Natural Resources and the Virginia Commission of Game and Fisheries have sponsored surveys to monitor populations and annual nesting success of great blue herons. They also monitor colonies of other species of herons and egrets. In early spring before the trees have leaves, aerial surveys are conducted to locate colony sites and count nests. At larger colonies, ground counts are made of active nests. Chesapeake Bay, the nation's largest estuary, and surrounding areas provide both the ideal food and habitat necessary for great blue heron survival. In 1990, surveys found 4600 great blue heron pairs in more than 38 colonies in Maryland. The Nanjemoy Creek colony in Maryland may be the largest along the entire Atlantic coast, with 1100-1200 nests counted in recent surveys. Fortunately, that land area is protected by the Nature Conservancy. In the past, herons and egrets were shot for their feathers, which were used as cooking utensils and to adorn hats and garments, and they also provided large, accessible targets. The slaughter of these birds went relatively unchecked until 1900 when the federal government passed the Lacey Act, which prohibits the foreign and interstate commercial trade of feathers. Greater protection was afforded in 1918 with the Migratory Bird Treaty Act, which empowered the federal government to set seasons and bag limits on the hunting of waterfowl and waterbirds. With this protection, herons and other birds have made dramatic comebacks

New Challenges

In recent years, great blue herons have had to face new challenges. Loss of nesting sites, and deterioration of water quality and wetland habitat are issues of concern for heron survival. Natural generation of new nesting islands, created when old islands and headlands erode, has decreased due to artificial hardening of shorelines with bulkheads. Poor water quality reduces the amount of large fish and invertebrate species available in wetland areas. If suitable feeding and nesting areas are not maintained, populations of great blue herons will eventually decline. Toxic chemicals that enter the Bay from runoff and industrial discharges pose yet another threat. Although great blue herons currently appear to tolerate low levels of pollutants, these chemicals can move through the food chain, accumulate in the tissues of prey and may eventually cause reproductive failure in the herons.

How to preserve nesting sites

Care must be taken to preserve nesting sites, as well as feeding areas. Erosion of island nesting areas due to artificial structural development, as well as sea level rise, needs to be carefully monitored. Nesting sites should be observed from a distance of at least 200 meters to minimize disruption of the colony. If herons are disturbed frequently, they may abandon their nests or neglect their young. Deterioration of submerged aquatic vegetation limits foraging area potential. Wetland foraging sites within 15-20 kilometers of heron colonies need special protection to ensure prey availability.

Currently, Chesapeake Bay is home to relatively stable, substantial populations of great blue herons, but we cannot become complacent in our efforts to preserve them. Preservation of shallow water habitat, feeding areas and rookeries must remain a priority if we want to continue to enjoy this majestic symbol of Chesapeake Bay.

Preservation Sites

Because herons often congregate in nesting rookeries, scientists are able to count the number of herons that inhabit the Bay region each year. Some rookeries are exceptionally large and are important preservation sites. The Bay provides ideal food and habitat for the blue heron’s survival. In 1990 surveys found 4,600 nesting pairs of great blue herons in more than 38 colonies in Maryland. At the Nanjemoy Creek Sanctuary near the Potomac River, volunteers counted more than 1,300 nests in that year. The area is under the stewardship of the Nature Conservancy.

Migratory Bird Treaty Act

Herons have not always been so well protected. In the late 19th and early 20th centuries, hunters shot herons, egrets and other birds with flamboyant plumage to collect their feathers for the millinery industry, and others shot the birds merely for sport. The heron was saved from extinction by the federal government’s passage of the Lacey Act, which forbids foreign and interstate trade of wildlife parts, and the Migratory Bird Treaty Act of 1918.