I have a keen interest in
birds since childhood and a long-held belief that scientific
enquiry is our best guide for conservation decisions. So it is
only fitting that my career has been spent conducting scientific
enquiries into the ecology and conservation of birds. My major
research has examined the social behaviour of crows, the
migration of sandpipers, and the ecology of herons.
I enjoy exploration and the
thrill of discovery of the connections between animals and their
environments, especially those that live along the seashore. The
findings have provide fodder for another keen interest of mine
to engage people with the animals around them. I have spoken to
countless groups and to the media about animals in our world
over the past 40 years. Much conservation work is done behind
the scenes providing advice to governments, companies, and
conservation organizations.
There is a strong interest by
the public to know more about great blue herons so below you
will find a summary of what we know about the heron in my home
province of British Columbia. You will also find a biography
including awards & service, and the organizations I am currently
working with on a variety of projects.
This year will be devoted to
the British Columbia Breeding Bird Atlas, establishing a Marine
Bird and Mammal Atlas and a program to identify important areas
for cetaceans. You can take a look at these projects by going to
the web sites of the
Bird Atlas
and the
Pacific WildLife Foundation.
You can also find out more from my blog at the Vancouver Sun.
Great Blue
Heron Research and Conservation
“Let it be borne in mind how
infinitely complex and close-fitting are the mutual relations of
all organic beings to each other and to their physical
conditions of life.” – Charles Darwin,
On the Origin of Species.
The Research
I am interested in how animals
find the balance between acquiring food needed to survive and
reproduce while avoiding being eaten by predators. A growing
body of information shows that the presence of predators can
have profound indirect effects on the behaviour of prey animals
and the environment they inhabit. Discovering these indirect
connections requires scientific sleuthing from an understanding
of the animals and their environment.
A Brief History of Heron Research
In the 1970s, little was known
about coastal herons in British Columbia. The pioneering studies
of John Kelsall, Keith Simpson and Scott Forbes laid the
groundwork for future behavioural and ecological work. They
conducted censuses of colonies, banded herons at colonies and
watched them at the breeding colonies and documented their
foraging behaviour. A comprehensive census of nesting colonies
in British Columbia was complied by Scott Forbes. At about the
same time, concern about contamination of herons from industrial
pollutants piqued the interest of Phil Whitehead and later John
Elliot, Ross Norstrum, Kim Cheng, Ian Moul, Darin Bennett, and
Leslie Hart. Their collective studies revealed much about the
breeding, physiology, contamination and growth of young herons.
My studies began in the mid 1980s examining the ecology herons
throughout the year. It was later augmented by research in the
field by Ross Vennesland, Jamie Kenyon and Iain Jones.
My early research showed that
herons nested near rich coastal foraging areas where they could
catch enough small fish in coastal shallows to produce eggs and
raise chicks. Predatory eagles have since increased so that
they are now an important consideration for where herons chose
to nest. Overlying the changing predator landscape is the
physical landscape we have built. Herons have had to cope with
city life, land clearing, shooting, and pollution. They served
as early warning systems for the build up of pernicious
industrial contaminants. We have also come to realize that
protecting the heron throughout its range would go a long way to
preserving habitats of high conservation value for many
species.
Taxonomy
The great blue heron and about
60 other species of herons belong to the genus Ardea. Its
closest living relatives are the lovely black-capped and
white-necked cocoi heron inhabiting the steamy tropical swamps
of Amazonia and temperate wetlands of South America, and the
similar looking grey heron of Europe and Asia. The triumvirate
great blue, grey and cocoi are thought to be especially closely
related and descended from a common ancestor that replace each
other geographically. Taxonomists refer to them as a
superspecies.
The great blue heron is
sufficiently different across its range that ornithologists have
divided it into four (and sometimes more) subspecies. Its range
is vast from the Pacific shores, across the mountains, prairies,
northern hardwoods and Atlantic shores of Canada, south through
the Atlantic seaboard and Florida Everglades west across the
Midwestern river courses and Rocky Mountain marshes to the surf
of California, the lagunas and mangroves of northern Mexico, and
the remote shoreline of the Galapagos. In autumn it departs
North American wetlands that become locked in winter ice and
snow for open water some migrating as far as South America. It
breeds from northern Mexico to southern Canada, and on the
Galapagos. Herons do not migrate from the Pacific Northwest,
southern USA, Mexico, and the Galapagos. Some herons in southern
Canada and the northern USA remain all winter long where
wetlands remain free from ice.
All of the four subspecies
have the typical great blue heron shape - long legs, long necks
and spear-like bills. The familiar adult great blue heron seen
across most of North America has grey-blue plumage on the back,
tail and wings, and neck, a whitish throat extending down the
neck edged with dark vertical markings, white crown with black
edges, and a yellowish bill. The scientific name is Ardea
herodias herodias which means the heron heron heron.
The great white heron is given
the unusual scientific name of Ardea herodias occidentalis
or western heron heron. It is an odd name for a mostly white
form of the familiar great blue that is confined to the Florida
Keys and part of the Caribbean. The Galapagos great blue heron
is a resident subspecies confined to the archipelago belonging
to Ecuador. It looks like a typical great heron except that the
plumage on the neck is somewhat pale and its legs have a decided
pinkish hue. Typical of herons, it wades in shallow water in
search of hapless fish. Nests are built in shrubs and trees. It
scientific name is Ardea herodias cognata or the heron’s
heron relative. The Pacific great blue heron resembles the
typical heron form except that the plumage is darker especially
on the neck, and the legs are shorter. Its scientific name is
Ardea herodias fannini named in honour of John Fannin,
former Director of the British Columbia Provincial Museum and
well known 19th century naturalist in Victoria.
Distribution
The Pacific great blue heron
nests from Washington to southern Alaska. In between, it resides
on coastal islands and in fjords of southeast Alaska and British
Columbia, and the coastal lowlands around Vancouver Island and
Puget Sound. Most Pacific great blue herons forage along the
seashore but a few also feed in freshwater marshes in the Fraser
River and Puget Sound lowlands. Herons nesting along the Olympic
Peninsula in Washington State are possibly Pacific great blues
whereas the herons in Oregon are probably not but this
distinction requires more investigation. Many herons reside in
urban areas of Vancouver, Victoria and Seattle and nest in large
colonies in urban parks and suburban areas. Others nest in very
remote locations away from all human activity including forests
along the BC and Alaska coastline.
Data from the recovery of
bands attached to heron nestlings in the Strait of Georgia show
that most do not leave the region. There are a few records of
bands recovered in the interior of British Columbia and as far
south as Oregon. Herons banded on the Sunshine Coast have been
recovered on Vancouver Island. Band recovery data reflect the
distribution of people as well as the movement of herons. It is
not surprising that most bands have been recovered in the region
but it is surprising that few have been found in the populated
regions of neighbouring Puget Sound in Washington State. Adult
herons have been seen flying across the Strait of Georgia
between the Fraser River and the Gulf Islands. These data
suggest that the heron population has very little immigration
and emigration. The implication of this conclusion is that the
effective population of herons might be quite small and
vulnerable to local action.
Evolution
of an Endemic Pacific Coast Subspecies
How did this subspecies arise
from pale-coloured herons that live to the east and south? We
know that herons roam widely. Recoveries of our banded birds
show that some herons travel great distances. Herons have
reached the Galapagos Islands and there are records for they
Yukon and Hawaii.
The coastal subspecies A.
h. fannini designation is based on phenotypic difference
from other great blue herons, most notably the darker colour and
shorter legs of the former. Robert Dickerman’s review of heron
plumage and measurements concluded that A. h. fannini
should be confined to the herons on Haida Gwaii and adjacent
mainland coast and southeast Alaska. His conclusion has not yet
been officially adopted and some genetic research could shed
some light on this issue.
There are several subspecies
of birds on Haida Gwaii that likely arose during a period of an
ice-free refugium during the late Wisconsin glaciation. An
ice-free plain connected the BC mainland to Haida Gwaii that
today is underwater. Pollen evidence from cores bored into the
submerged plain tells of an ancient land of freshwater lakes and
marshes similar to where herons live today. Mitochondrial DNA
evidence from a suite of other species from mosses to bears
points to this submerged land as the Eden for many coastal
subspecies now living on higher ground among the islands along
the BC coast. In the isolation of the ice-free refugia, a small
population of herons could have begun to adapt to a wet coastal
environment. As the ice melted further, the heron extended its
range along the coast into present day Alaska and toward
Vancouver.
If the southern border of
A. h. fannini is the central coast of BC, then what
designation should be applied to the great blue heron near where
I live on the south coast of BC? Herons on the south coast are
larger than their northern relatives and smaller than California
specimens.
Facts
Scientific name: Ardea
herodias fannini
Distribution: Eastern Pacific
shoreline and all fjords and large islands between Puget Sound,
Washington (Olympia) and southern Alaska (Kodiak)
Non-migratory. Disperses to
foraging habitats along seashore mostly near nesting areas but
some young herons have traveled hundreds of kilometers
Food: Mostly small fish but
also crabs, small mammals, snakes and birds. Most foraging is
within a few kilometers of the nesting colony. Maximum distance
is about 10 kilometers. Prey items are killed and swallowed
whole. Food is carried to the nest in the throat and
regurgitated into the nest.
Mating Strategy: Mostly
monogamous pairs during nesting season. Probably choose new
mates in subsequent years.
Eggs Stage: 3-5 pale blue
eggs are laid in April and May. Second nesting attempts are made
until June. Incubation is about 27 days. Eggs hatch
asynchronously.
Chick Stage: Chicks are
brooded by both parents nearly continually for about 3 weeks
post hatching. Female parents forage mostly during the day and
incubate and brood at night. Males do the opposite. After about
three weeks, both parents forage during the day. Chicks perch in
branches of trees and depart the nest after about 55 days of
age.
Life Span: Uncertain but
based on survival of marked herons, most adults probably live
about 10 years and some probably live to be about 20 years.
Conservation Status: Schedule
3 in Canada’s Species at Risk Act (March 2010). When a species
is added to Schedule 1 as a species of special concern, SARA
requires the preparation of a management plan to prevent them
from becoming endangered or threatened.
Population Size: About 10,000
herons across the range. About 1000 to 1500 nesting pairs around
the Strait of Georgia, 2000 pairs around Puget Sound. Scattered
along the coast north to southern Alaska. The population on
Haida Gwaii (the site of the fannini type specimen) is
probably no more than 100 pairs.
Age of maturity: Most at two
years although some yearlings attempt to breed.
Birth Rate: About 2 young per
successful nesting attempt. Nesting success is highly variable
with abandonment being a major factor.
Recognizing Herons
Eggs
Great blue herons lay pale
blue eggs measuring about 6 cm long and 4 cm in diameter.
Freshly laid eggs weigh about 70 grams. Adult herons have
brightly coloured bills and feather plumes on their breasts a
few weeks before and during egg laying. The colours fade and the
plumes are shed soon after eggs are laid.
Nestlings
Chicks at hatching have
sparse grey down on the body and wings, a tuft of whitish
feathers on the crown and stout wing and pinkish grey legs. They
will sport these white tufts until soon after they leave the
nest. Newly hatched chicks utter a faint tik-tik-tik sound
within minutes of hatching. They grow quickly first to a
crouching position and then to a standing position. The calls
get louder and more raucous that is unending day and night. The
young herons perch on the nest before moving into branches in
the nest tree to practice flapping their wings. One or two
nestlings are often killed, starved or fall to their deaths.
Parents that succeed, can expect to raise an average of slightly
more than two chicks.
Juveniles
A heron is a juvenile from
when it leaves the nest until the start of the following
breeding season. Juveniles lack the body plumes, white crown
feathers, black occipital (eye) plume of the breeding adult.
Their crown feathers are slate gray. Their wing coverts are
edged with cinnamon brown tips, and the feathers on the neck are
generally streaked brown.
Yearlings
A juvenile becomes a yearling
when it is 12 months old. Yearlings resemble adults except that
they have a small amount of white on the crown. The edge of some
wing coverts are tipped with brown. They have short or no
plumes.
Adults
A heron becomes an adult when
it is two years old. They are generally a slate grey on the back
and hind neck. The crown is white and the forehead varies from
white to grey. This feature might be age-related. A black plume
emerges from the posterior end of a black line above the eye.
The eye is yellow rimmed with black. The bill is greenish grey
on the upper mandible and yellowish on the lower mandible during
the non-breeding season. The bill turns yellowish-orange during
courtship and egg laying. The side of the neck is buffy brown,
especially in the coastal subspecies. The foreneck is white with
cinnamon and chocolate brown streaks. Plumes on the breeding
adult spill from the back over the folded wing and sprout from
the chest. Some of these feathers are dropped soon after the
eggs are laid. The primary flight feathers and the flanks are
black. The bend of the wing and the upper legs are cinnamon
brown. The legs are greenish grey with yellow-green soles. Sexes
are similar although females are generally slightly smaller than
males. This difference is most pronounced in bill length.
Best Places to See Herons
A large nesting colony of
300-400 pairs gathers between March and July at the foot of the
BC Ferry terminal at Tsawwassen south of Vancouver each year.
You can park alongside the terminal road at a pull out on the
east side where there are superb views of herons on nests and
flying to the tidal flats to catch fish. With binoculars, you
can see up to 800 herons foraging on the nearby beach.
Over 100 pairs nests in trees
each spring near the headquarters of Stanley Park in downtown
Vancouver. Enter the park from Beach Avenue.
Further Reading
Butler, RW. 1997. The great
blue heron. University of British Columbia Press, Vancouver.
This book summarizes much of what I have learned about herons
and my experiences following them around the year.
Butler, RW. 1992. Great Blue
Heron (Ardea herodias). The Birds of North America (A.
Poole, Ed.). Ithaca: Cornell Lab of Ornithology. Online:http://bna.birds.cornell.edu/bna/species/025
