Photo by Jack Bartholmai
Status/Protection
- Global Rank: G5 Key to global and state ranks
- State Rank: S2B
- WBCI Priority: SGCN, State Threatened
Population Information
The Federal BBS information can be obtained at http://www.mbr-pwrc.usgs.gov/bbs/bbs.html by clicking on Trend Estimates and selecting the species in question. All estimates are for time period (1966-2005).
- Federal Breeding Bird Survey: significant increase
- Federal Breeding Bird Survey (WI): non-significant decline
- Federal Breeding Bird Survey (BCR 23): N/A
- Federal Breeding Bird Survey (BCR 12): non-significant decline
- WSO Checklist Project: significant increase (1983-2007)
Life History
- Breeding Range: Scattered inland and coastal locations throughout the U.S., Mexico, and Central and South America (McCrimmon et al. 2001).
- Breeding Habitat: Bottomland Hardwood.
- Nest: Platform of sticks in tree or tall shrub (Ehrlich et al. 1988).
- Nesting Dates: Eggs: early May to late June (Robbins 1991).
- Foraging: Stalk and strike (Ehrlich et al. 1988).
- Migrant Status: Short-distance migrant, Neotropical migrant.
- Habitat use during Migration: Emergent Marsh, Northern Sedge Meadow and Marsh, Southern Sedge Meadow and Marsh; freshwater and saltwater wetlands, estuaries (McCrimmon et al. 2001).
- Arrival Dates: Late March to late May (Robbins 1991).
- Departure Dates: Late July to mid-November (Robbins 1991).
- Winter Range: Southern U.S., West Indies, Central America (DeGraaf and Rappole 1995, McCrimmon et al. 2001).
- Winter Habitat: Similar to breeding and stopover habitats (McCrimmon et al. 2001).
Habitat Selection
The Great Egret nests in colonies ranging in size from several pairs to thousands of pairs, often in association with Great Blue Herons (Fruth 1988). Foraging habitat can dictate the size and location of breeding colonies (Fruth 1988, Custer et al. 2004). For instance, the Upper Mississippi River floodplain habitats provide abundant, shallow backwater habitats for foraging (i.e., sloughs, shallow lakes, and ponds downstream of a lock and dam) and support 4-7 nearby colonies of 100-300 pairs (Nelson and Wlosinski 1999, Custer et al. 2004). Elsewhere Great Egrets forage in stream and river edges, tidal pools, drainage ditches, and ponds used for commercial fish production (McCrimmon et al. 2001). Distances traveled from colony sites to foraging areas varies geographically but in Wisconsin has not exceeded 35 km (Fruth 1988).
Habitat Availability
Wisconsin is on the extreme northern edge of the Great Egret breeding range (McCrimmon et al. 2001) where it is considered an uncommon summer resident in the west, south, and east and rare in the central part of the state (Robbins 1991). Horicon Marsh/Lake Winnebago wetlands and the Mississippi River floodplain forests provide suitable colony sites in most years. However, the primary colony site (i.e., Four Mile Island) at Horicon Marsh was destroyed during a windstorm in 1998 and no longer supports a nesting colony (Volkert 2006). The widespread loss of floodplain forests has reduced the amount of suitable nest sites in the state. Although bottomland hardwood and other floodplain forests have fared better than many of Wisconsin’s native habitats, it is estimated that only 8% of presettlement floodplain forest remains in moderate to high quality condition (Mossman 1988). Invasive plant species, particularly reed canary grass, may impede regeneration in floodplain forests and development pressures also threaten remaining stands (WDNR 2005). The loss and degradation of wetland ecosystems within the state also impacts this species by reducing the quality and quantity of feeding sites. At existing foraging habitat, pollution and toxic contamination may reduce necessary food resources and thereby render nearby colony sites unsuitable (Fruth 1988).
Population Concerns
Historically, the Great Egret was considered to be a common species within appropriate habitats of Wisconsin (Kumlien and Hollister 1903, cited in Fruth 1988). Plume hunting in the late nineteenth century decimated Great Egret populations throughout North America and resulted in the extirpation of many local populations. The Wisconsin population declined precipitously during this era, with the last breeding attempt occurring in 1886. Protection efforts in the early twentieth century led to a rapid population recovery and Great Egrets were again breeding in Wisconsin by 1939 (Fruth 1988). Since that time, the number of nesting colonies statewide has fluctuated from as few as five to as many as ten during the recent Breeding Bird Atlas work; however, only two of the Atlas sites contained >10 pairs (Volkert 2006). Both the species’ rarity and its colonial nesting behavior make it difficult to determine its population status in the state. Wisconsin Breeding Bird Survey data suggest a non-significant population decline, but Wisconsin Checklist Project data indicate a significant increase in the state population (Sauer et al. 2005, Rolley 2005). The inconsistency of these results highlights the need for a targeted long-term monitoring program for this and other colonial waterbird species. Elsewhere in its range, the Great Egret appears to be experiencing a significant population increase (Sauer et al. 2005).
Reductions in the quantity and quality of foraging and nesting habitats may be the primary factors limiting Great Egret populations (McCrimmon et al. 2001, Custer et al. 2004). Logging of floodplain forests, draining of wetland complexes, and contamination and pollution of extant wetlands have contributed to the widespread habitat loss and degradation.
Recommended Management
An inter-agency partnership of state and federal agencies, private and non-profit conservation partners is needed to determine common goals and strategies for Great Egrets and other colonial waterbirds along the Upper Mississippi River and throughout the state (WDNR 2005). The protection and restoration of wetland complexes on public and private lands is of primary importance in managing this species. For private landowners, managers should develop information materials for enhancing/restoring their properties for Great Egrets and other herons (Fruth 1988). Protecting existing colony sites is essential to maintaining colonial waterbird populations in the state, including the Great Egret, Snowy Egret, and Black-crowned Night-Heron. At existing colony sites managers should: (1) institute protection measures for nearby foraging areas; (2) maintain water depths of foraging areas <28 cm; (3) reduce or eliminate the discharge of chemical contaminants; (4) reduce or eliminate human disturbances; (5) experiment with techniques to promote tree regeneration and to test the effectiveness of artificial nesting platforms; and (6) determine and implement measures to control predators at colony sites (McCrimmon et al. 2001, Custer et al. 2004, WDNR 2005). Although protection of existing colonies is essential, it is equally important to protect apparently potential habitat for colony expansion and colonization of new sites. Conservation efforts for this species should be focused in the following Wisconsin ecological landscapes: Central Lake Michigan, Northern Lake Michigan, and Western Coulee and Ridges (WDNR 2005).
Research Needs
More study is needed on the management techniques required to create, restore, or improve Great Egret nesting and foraging habitat in Wisconsin. A statewide inventory of suitable nesting and foraging habitat would better guide future conservation efforts. A long-term monitoring program for Great Egrets and other colonial waterbirds of Wisconsin is urgently needed and should evaluate population dynamics, food resource use, health and longevity of nesting and feeding sites, habitat productivity, and contaminant levels and effects (Fruth 1988). Study of a color-banded population could aid in studies of mortality and migration movements, survivorship, and other demographics. Researchers should continue to monitor and assess the effects of chemical contamination on Great Egrets and other wading birds (McCrimmon et al. 2001).
Information Sources
- Chequamegon National Forest Bird Survey species account: http://www.nrri.umn.edu/mnbirds/accounts/GREGa2.htm
- Cornell Lab of Ornithology species account: http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Great_Egret.html
- Horicon Marsh Wildlife page: http://dnr.wi.gov/org/land/wildlife/reclands/horicon/nathist/wildlife/#art3
- Illinois Natural History Survey page: http://www.inhs.uiuc.edu/chf/pub/ifwis/birds/great-egret.html
- North American Breeding Bird Survey: http://www.mbr-pwrc.usgs.gov/bbs/bbs.html
- Waterbird Conservation for the Americas: http://www.waterbirdconservation.org/pubs/ContinentalPlan.cfm
- Wisconsin Breeding Bird Atlas: http://www.uwgb.edu/birds/wbba/
- Wisconsin Department of Natural Resources factsheet: http://www.dnr.state.wi.us/org/land/forestry/publications/endangered/PDF/SPECIES/Birds/GREgret.pdf
References
- Custer, C.M., S.A. Suárez, and D.A. Olsen. 2004. Feeding Habitat Characteristics of the Great Blue Heron and Great Egret Nesting Along the Upper Mississippi River, 1995-1998. Waterbirds 27(4): 454-468.
- DeGraaf, R.M., and J.H. Rappole. 1995. Neotropical migratory birds: natural history, distribution, and population change. Comstock Publ. Assoc., Cornell Univ. Press, Ithaca, NY.
- Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The birders handbook: a field guide to the natural history of North American birds. Simon & Schuster, Inc. New York.
- Fruth, K.J. 1988. Wisconsin Great Egret recovery plan. Bureau of Endangered Resources, Wisconsin Department of Natural Resources, Madison, WI.
- McCrimmon, D.A., Jr., J.C. Ogden, and G.T. Bancroft. 2001. Great Egret (Ardea alba). In The Birds of North America, No. 570 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
- Mossman, M.J., and D.W. Sample. 1990. Birds of Wisconsin sedge meadows. Passenger Pigeon 52(1): 39-55.
- Nelson, E.C. and L.B. Wlosinski. 1999. Wetland birds of the Upper Mississippi River National Wildlife and Fish Refuge. Passenger Pigeon 61(3): 299-305.
- Robbins, S. D. 1991. Wisconsin birdlife: population & distribution, past & present. Univ. of Wisconsin Press, Madison, WI.
- Rolley, R. 2005. Wisconsin Checklist Project. http://dnr.wi.gov/org/land/wildlife/harvest/reports/07checklist.pdf (23 April 2007)
- Sauer, J.R., J.E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, Results and Analysis 1966 - 2005. Version 6.2.2006. USGS Patuxent Wildlife ResearchCenter, Laurel, MD.
- Thompson, D.H. 1978. Feeding areas of Great Blue Herons and Great Egrets nesting within the floodplain of the upper Mississippi River. Colonial Waterbirds 2: 202-213.
- Volkert, W.K. 2006. Great Egret. In Atlas of the Breeding Birds of Wisconsin. (N.J. Cutright, B.R. Harriman, and R.W. Howe, eds.). The Wisconsin Society for Ornithology, Inc. 602pp.
- Wisconsin Department of Natural Resources (WDNR). 1995. Wisconsin’s Biodiversity as a Management Issue. Online at http://dnr.wi.gov/org/es/science/publications/rs915_95.htm
- Wisconsin Department of Natural Resources (WDNR). 2005. Wisconsin’s Strategy for Wildlife Species of Greatest Conservation Need. Madison, WI. http://www.dnr.state.wi.us/org/land/er/wwap/explore/
Contact Information
- Compiler: William P. Mueller, iltlawas@earthlink.net
- Editor: Kim Kreitinger, K.Kreitinger@gmail.com