Conservation and Management

Shooting And Trapping

Shooting of adults at colony sites by plume hunters from 1880 to 1910 well-documented. Consequent loss of breeding cohort and current year’s offspring quickly led to local extirpation in s. North America (see Distribution: historical changes, above).

Pesticides And Other Contaminants

DDE detected in 100% of eggs (19 eggs, n = 19 clutches) collected in Idaho (1979); other organochlorines generally insignificant (Findholt 1984). In San Francisco Bay (1982), eggs contaminated by organochlorines and mercury (Hg); contained 2.04 ppm (parts per million) DDE (wet weight, geometric mean), 3.29 ppm total PCBs, and 0.21 ppm Hg (n = 10 nests; Ohlendorf et al. 1988). In Oregon and Nevada, PCBs undetected in eggs, but nests containing eggs with >5 ppm DDE had low hatching and fledging success compared to uncontaminated nests (Henny et al. 1985). Cholinesterase depression (a toxic lowering of critical neural enzyme levels) of nestlings in agricultural areas may result from exposure to modern pesticides (Parsons et al. 2000). Fenthion, which caused lethal cholinesterase depression, which in turn influences activity rates, was implicated in 7 deaths in California (Zinkl et al. 1981). See Demography and populations: causes of mortality, above.

Ingestion Of Plastics, Lead, Etc

In New York Harbor, 10% of 54 nestling regurgitations included inert material such as resin pellets and styrofoam (KCP).

Degradation Of Habitat

Loss of foraging habitat as a result of oil spills in New York Harbor (Fig. 4) led to significant nestling mortality from starvation (Parsons 1994).

Direct Human/Research Impacts

Based on extensive banding of 2,360 nestlings, Swepston et al. (1978) concluded banding had minimal impact on survival. Nestlings also relatively insensitive to varying levels of investigator disturbance (Davis and Parsons 1991). Breeders relatively undisturbed by helicopter and fixed-wing aircraft surveys of nesting colonies (Kushlan 1979). Response to human disturbance (boats, noise) at foraging sites minimal compared to that of other waterbirds (Bratton 1990, Klein 1993).

Conservation Status

Species of Special Concern in Florida (Edelson and Collopy 1990), threatened in Connecticut (1994). Despite limited data, it is apparent that populations along most of the Atlantic coast appear to be declining (see Demography and populations: population status, above).

Measures Proposed And Taken

Species protected in North America since 1916 under the Migratory Bird Treaty Act. Decline in Florida in 1990s has renewed calls for monitoring and scientific study (Rodgers et al. 1996). In New Jersey, colony-site restoration is being attempted in Stone Harbor using Great Egret models to lure individuals back to a former colony site that was inhabited for 50 yr. Model presence may be augmented with colony sounds in the future (KCP, TLM).

Identified as a species impacting aquaculture facilities, especially in the South.

Delineation of important wintering areas in the tropics is crucial to continued maintenance of continental heron populations (Parnell et al. 1988). Key areas include Cuba, the Greater Antilles, the Bahamas, and the Gulf and Pacific coasts of Central America (Mikuska et al. 1998).

Effectiveness Of Measures

Remarkable range expansion following establishment of the Migratory Bird Treaty Act is best evidence of species’ ability to respond to protective/management measures (see Distribution: historical changes, above).