Great Blue Heron fannini subspecies
Scientific Name: Ardea herodias fannini
Other/Previous Names: Pacific Great Blue Heron
Taxonomy Group: Birds
Range: British Columbia
Last COSEWIC Assessment: April 2008
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern
Image of Great Blue Heron fannini subspecies
Five subspecies of Great Blue Heron are currently identified, two of which reside in British Columbia. The herodias subspecies resides in all of southern Canada east of the Coastal Mountains of British Columbia, whereas the fannini subspecies resides on all of British Columbia's coast west of these mountains.
The Great Blue Heron is the largest heron in Canada. Standing over 1 m in height with its neck extended and measuring 97 to 137 cm in length, it is also the largest wading bird in North America. Like all wading birds, the Great Blue Heron has long, stilt-like legs, a long neck and a short tail. Its wings are long and rounded. The Great Blue Heron flies with deep, slow wingbeats, its neck folded in an S-shape and its head pressed between its shoulders. Its long, slender digits are partially webbed. Plumage is mostly a blue-grey colour, and adults have a white crown with a black stripe extending from the yellow eyes to slender black plumes at the back of the head. Its breast is white streaked with black. The Great Blue Heron fannini subspecies is smaller and darker in colour than the Great Blue Heron herodias subspecies. It also differs in its reproductive behaviour and its reproductive physiology; in particular, it has a smaller clutch size.
Distribution and Population
The Great Blue Heron breeds in most regions of North America south of Alaska, and on the Galapagos Islands. The winter distribution of this species is south of the polar regions in the North to as far south as Panama. The Great Blue Heron fannini subspecies resides year-round on the Pacific Coast, where it is confined to a region extending from Prince William Sound in Alaska to Puget Sound in Washington State. In Canada, the presence of this subspecies is limited to the north and south coasts of British Columbia, and to its large coastal islands, including Vancouver Island and the Queen Charlotte Islands. Most of these herons breed in the Strait of Georgia. This non-migratory species is isolated in part from continental herons by the high mountain ranges to the east. It is difficult to estimate population size for the Great Blue Heron fannini subspecies because colonies are not stable: herons have a tendency to leave the colony following a disturbance. The best available estimates suggest that its population in Canada is 4000 to 5000 nesting adults, nearly half of its global population. Christmas Bird Count data show significant population declines of 19 to 26% over the past three generations of herons, while Coastal Waterbird Surveys show an increase from 1999 to 2004, but these surveys cover only a five-year period. Colony surveys suggest that the reproductive rate for herons has declined considerably since the 1970s. The proportion of nesting pairs that successfully raise at least one fledgling on the coast of British Columbia is currently much lower than in the past. Immigration from United States populations is theoretically high because of the proximity of Puget Sound in Washington State and of the Strait of Georgia, and because of the roughly equal-sized heron populations in the two regions. However, threats to heron populations and habitats in the United States are similar to those in Canada, and perhaps even more severe because of the larger human population living there.
The Great Blue Heron fannini subspecies forages along the seacoast, in fresh and saltwater marshes, along rivers and in grasslands. Smaller numbers of herons forage in kelp forests, from wharves and at anthropogenic waterbodies, such as ornamental ponds and fish farms. Most herons nest in woodlands near foraging areas. They build their nests in a variety of species of trees, including Red Alder, Black Cottonwood, Bigleaf Maple, Sitka Spruce and Douglas-fir. A suitable nesting site must include an established colony and alternative sites that can be used in case of disturbance. Some colonies are used for many years, but most colonies, especially those with fewer than 25 nests, are relocated every few years. In the fall, juvenile herons occupy grasslands on the Fraser River delta and southern Vancouver Island, and adults occupy estuarine marshes, riverine marshes and grasslands. The size of Great Blue Heron populations is correlated with the area of foraging habitat available locally. Consequently, the largest concentrations of herons of the Great Blue Heron fannini subspecies are found around the Fraser River delta, which provides abundant foraging locations. Local declines in foraging locations have likely been greatest in south-coastal British Columbia because most of the province's human population is located in this area. Furthermore, use of some foraging areas may be limited by the amount of nesting habitat that remains undeveloped. Although the Pacific Great Blue Heron population is non-migratory, the birds move between various locations in the Strait of Georgia over the course of the seasons. From March to October, most adults and juveniles forage along beaches; in winter, they make use of prairies and marshes. Over the past century, the abundance of large trees suitable for nesting near foraging areas has declined in some parts of British Columbia because of human population growth and industrial development. The south coast of the province, particularly the Lower Fraser Valley, where the human population is very large and still growing, has been hit especially hard by this phenomenon. In this region, the lack of nesting habitat might be limiting the size of the heron population. From 1972 to 1985 and from 1998 to 1999, habitat destruction on the south coast of British Columbia resulted in the abandonment of at least 21 colonies. Over the past century, the abundance of large trees suitable for Great Blue Heron nesting near foraging areas has declined in some parts of British Columbia because of human population growth and industrialization. Suitable foraging habitat is likely also declining in the province, though no quantitative information is available in this regard.
On the south coast of British Columbia, the Great Blue Heron fannini subspecies begins to nest between February and April. At this time, most herons gather in colonies where they court, nest and raise their young. Monogamous couples are then formed for the season. Females typically lay four eggs, and on average, fewer than two chicks reach the fledgling stage and leave the nest. The Great Blue Heron fannini subspecies has smaller clutches than those of other Great Blue Herons, which range in size from one to eight eggs. The male and female both incubate the eggs and feed their young. Less than 25% of juvenile herons survive their first winter. The nests, generally built in trees, consist of large platforms made of large branches. Sometimes, herons simply repair a nest used the previous year. Couples nest alone or in colonies. Herons hunt a wide variety of animals, but their diet consists mainly of small fish during breeding season, and is supplemented with small mammals in winter. In British Columbia, the primary predator of the Great Blue Heron fannini subspecies is the Bald Eagle. The Bald Eagle is responsible for reduced nesting productivity in many colonies.
The main factors threatening heron populations are nesting failure and reduced nesting productivity as a result of eagle predation, human disturbance and destruction of nesting and foraging habitats by residential and industrial development, road construction and logging. The quiet wooded areas in which herons nest, located near foraging areas, are becoming increasingly rare in southern British Columbia. The human population in the area of the Strait of Georgia, in which is concentrated the largest number of herons, is projected to double from 1990 to 2020, which may increase human disturbance in colonies, as well as habitat destruction. Although some herons of the Great Blue Heron fannini subspecies can tolerate human activities near their nests, many are sensitive to human presence. Human activity near heron colonies compounds the threat posed by eagle predation to this subspecies. It has been shown that the number of fledglings raised in Great Blue Heron colonies with frequent disturbances is significantly lower than in colonies with no disturbances. When disturbed, herons leave their nests unguarded, especially early in the nesting season when humans enter colonies on foot or make noise nearby. Unprotected nests leave eggs and chicks more vulnerable to predation by eagles and other birds. The Bald Eagle is the primary predator of the Great Blue Heron fannini subspecies and represents a factor that significantly affects heron populations. Eagle populations on the south coast of British Columbia have been on the rise since the mid-1980s and the number of attacks on Great Blue Heron nests has more than doubled over this time period. Predation and associated disturbance result in significantly higher nest and colony abandonment rates. In addition, predators may have an impact on habitat quality by forcing herons to move to new sites that are even more limited or of lower quality. Finally, chemical contaminants such as polybrominated diphenyl ethers, or PBDEs, are found in increasingly high concentrations in the tissues of herons and could reach toxicologically significant levels. The implications of this finding are currently not fully understood, but the situation is seen as a potential emerging threat in urban areas. There are similar concerns over another emerging class of industrial pollutants: perfluorinated chemicals.
Federal ProtectionMore information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
In British Columbia, the Great Blue Heron, its nests and its eggs are protected by the province's Wildlife Act. The Great Blue Heron is protected by the Migratory Birds Convention Act, 1994. This Act prohibits the harming of birds, their nests or their eggs.
Provincial and Territorial Protection
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
13 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- COSEWIC Assessments (1 record(s) found.)
- Response Statements (1 record(s) found.)
- Action Plans (4 record(s) found.)
- Management Plans (1 record(s) found.)
- Orders (2 record(s) found.)
- COSEWIC Annual Reports (1 record(s) found.)
- Consultation Documents (1 record(s) found.)
- Recovery Document Posting Plans (1 record(s) found.)
COSEWIC Status Reports
COSEWIC Annual Reports
Recovery Document Posting Plans
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