Download Aves (Birds): Ciconiiformes, Ardeidae Great Blue Heron (Ardea

Aves (Birds): Ciconiiformes, Ardeidae
Great Blue Heron (Ardea herodias)
Potential Occurrence: Rookeries Unlikely to Occur
Status: (Rookery Sites)
Federal: none
State: none
Other: MBTA; CDF:S
Species Description: The largest of the North
American herons, the Great Blue Heron has a head-toPhoto: © Walter Siegmund
tail length of 36-55 inches, a wingspan of 66-79 inches,
and weighs between 4.4 to 8 pounds (del Hoyo 1992). As a wading bird, the Great Blue Heron
has long legs, a long neck, a long, and a thick yellow beak. Their wings, belly, and back are
blue-grey and a white face with black plume extending from the head. They fly with their necks
folded, as opposed to cranes which fly with their necks outstretched (Clarke 1976).
Distribution: The Great Blue Heron is widely distributed in North America and is a year-round
resident in much of California, including the North Coast region (Hammerson 1996).
Life History & Threats: Nests are large, bulky, and made of sticks and usually the herons
breed in colonies of a few pairs to hundreds. Nests are often high in trees but occasionally may
be built on the ground (Clarke 1976; Hammerson 1996). Both parents care for a clutch of 3-7
eggs and nestlings fledge the nest in 60-90 days. Great blue herons eat a diet of mostly fish, but
also frogs, insects, and mice, which are caught by patient stalking. Like other aquatic predators,
they are threatened by pollutants and pesticide runoff that makes its way up the food chain
(USFWS 2009). Nesting colonies can be threatened by human disturbance and by Bald Eagle
predation (Hammerson 1996). A 300 m buffer zone around the colony with no human activity is
recommended during courtship and nesting (Butler 1992).
The great blue heron has a remarkable ability to exploit a wide range of habitats and food types.
Consequently it is widespread and abundant, and is not subject to any major threats at the
species level (4) (6). Nonetheless, some populations, particularly those occupying small areas on
the coast, are vulnerable to localized impacts (4). This broadly includes habitat destruction,
human disturbance and persecution, and contamination by pollutants (2) (4). (From ARKive
2010)
Habitat & Habitat Associations:
Foraging Habitat: freshwater and brackish marshes, along lakes, rivers, bays, lagoons, fields
and meadows (Hammerson 1996).
Great blue herons always live near sources of water, including rivers, lake edges, marshes,
saltwater seacoasts, and swamps. They tend to avoid marine habitats along the east coast and
instead live inland (Ferguson, 1998 ). (From ARKive 2010)
Nesting Habitat: Great Blue Herons usually nest in trees or bushes that stand near water,
breeding at elevations of up to 1,500 m (ARKive 2010). Will nest within 16 km (10 miles) of
feeding area (Krebs 1974).
Generally, the great blue heron nests in tall trees that are near to aquatic feeding areas, and are
to some extent isolated from human disturbance (4). However, when trees are not available, it will
also nest on the ground in areas free from predators, and in reeds, shrubs and mangroves (2).
Although some nest singly, many breed in colonies, which vary in size depending on the amount
of nearby foraging habitat (2) (4). (From Arkive 2010)
Herons nest in a variety of forests in rural, residential and urban areas. Colonies are located
within about 10 kilometers (16 miles) of the foraging areas. The area of the foraging area
determines the number of herons that will nest in the neighbourhood. (From Heron Working
Group 2010)
Species Associations: Trees used for nesting include pine, cypress, eucalyptus (Aquarium of
the Pacific 2010). Old great blue heron nests are sometimes used by Great Horned Owls, Long
Eared owls, and other birds.
Conceptual Basis for GIS Model Development: To identify potential habitat for the Great Blue
Heron in the Study Area, we mapped potential foraging and nesting habitat as:
Foraging Habitat:

bare soil (nearly all bare ground within the study area at GIS-visible scales represents
flood plains or other water-adjacent features)

grasslands

riparian vegetation (i.e., Fremont Cottonwood vegetation)

ponds, drainages, and creeks
Nesting Habitat: Because the Study Area is within 16 km of the main stem of the Navarro River,
a productive feeding area, we considered the entire Study Area as suitable nesting habitat. We
mapped the possible best nesting habitat as large dense coniferous forest (i.e., RedwoodDouglas fir mix or Pacific Douglas fir vegetation with canopy cover > 70 and a DBH > 24
inches).
Potential Occurrence in the Galbreath Wildlands Preserve: Protection status for this species
applies to nesting rookeries.
Habitat: Great Blue Herons prefer trees and bushes located with 10-15 km of rookery sites. The
entire Study Area was considered potential nesting habitat due to the location of the Preserve
near the mainstem of the Navarro River, a productive feeding area.
Rookery habitat quality varies from moderate in the Preserve is good. The best potential nesting
areas, characterized by large coniferous with dense canopy cover, are patchy throughout the
Preserve; the largest patch is located in the northeast corner of the Preserve (Figure 78).
Nearest Occurrence:
Documented Occurrences in Preserve: This species has not been documented in the
Preserve. To our knowledge, no surveys have been conducted.
Nearest Occurrence to Preserve: Rookeries have not been reported to occur in USGS
quads adjacent to the Preserve.
Summary: While the Preserve contains high quality habitat for Great Blue Heron rookeries, we
expect that rookeries are “Unlikely to Occur.” Herons prefer to nest near productive foraging
areas, such as the mainstem of the Navarro River. With the abundance of large, densely
forested slopes in the watershed, it is unlikely that rookery nest are limiting in the Navarro River
watershed. We anticipate that rookeries are more likely to occur in areas west of the Preserve
near the mainstem.
References
ARKive 2010. Great blue heron (Ardea herodias) ARKive Images of Life on Earth.
<http://www.arkive.org/great-blue-heron/ardea-herodias/info.html>. 2010 July 10.
Butler, Robert W. 1992. Great Blue Heron (Ardea herodias), The Birds of North America Online
(A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology. <http://bna.birds.cornell.edu/bna/species/
025>. 2010 July 7.
Clarke H, Small A. 1976. Birds of the west. Cranbury, New Jersey: A.S. Barnes and Co., p 56.
Del Hoyo J, Elliot A, Sargatal J. 1992. Handbook of the birds of the world. Volume 1. Barcelona:
Lynx Edicions.
Granholm SL. 1988-1990. California’s Wildlife Vol. I-III. Life History Account for California
Wildlife Habitat Relationships System, Great Blue Heron. Sacramento: California Department of
Fish and Game.
Hammerson G. 1996 April 30. Comprehensive Report Species – Ardea herodias. NatureServe
Explorer. Version 7.1. <http://www.natureserve.org/explorer>. 2010 July 6.
Heron Working Group 2010. <http://www.heronworkinggroup.org/heronnetwork.htm>. 2010 July
10.
Krebs JR. 1974. Colonial nesting and social feeding as strategies for exploiting food
resources in the great blue heron (Ardea herodias). Behavior 51:99-134.
United States Fish and Wildlife Service, Northeast Region. 2009 Nov 3. Great Blue Heron.
Chesapeake Bay Field Office. <http://www.fws.gov/chesapeakebay/heron.html>. 2010 July 6.
Unknown author. 2010. Great Blue Heron Summary. Aquarium of the Pacific Online Learning
Center. <http://www.aquariumofpacific.org/onlinelearningcenter/species/great_blue_heron/>.
2010 July 6.
Photo Info: Used under Creative Commons license, from <http://commons.wikimedia.org/wiki/
File:Ardea_herodias_01997t.JPG>. 2010 July 5.
Species Account Description: Kandis Gilmore and Emily Harvey