The herons of the world are a large and interesting family, having ancient
origins stretching back to the Lower Eocene some 55 million years ago (Martínez-Vilata
& Motis 1992). Most are associated with water and are nicely adapted
for preying on fish, frogs, and other marsh denizens. Payne & Risley
(1976) divided the family into four major branches or subfamilies: the
night-herons (with large eyes for feeding in the dark, as does the Yellow-crowned
Night-Heron, left; this subgroup also includes the Boat-billed Heron
Cochlearius
cochlearius of the Neotropics which had once been placed in its own
family); the day-herons (our "usual" herons and egrets, most of which forage
in the water or along shores, as does the Little Blue Heron, below
right); the tiger-herons of the tropics; and the bitterns (including the
enigmatic Zigzag Heron Zebrilus undulatus of South America). While
tiger-herons and bitterns are secretive and difficult to observer, day-herons
& egrets around the world are easy to watch. Frequently, marshland
scenes are full of herons and egrets. Often they nest is large noisy colonies.
The sheer abundance and variety of herons in swampy lowlands can be
staggering. Early morning or evening flights of herons in the Florida everglades
or Texas coast is a memorable spectacle. While all this does make herons
well-known to people in general, it also places them at risk. Colonies
must be well-protected from predators and disturbance to survive.
Most of the herons can be divided up into Old World and New World species, and often there are close replacements in the two regions, such as the Snowy Egret Egretta thula of the New World which is closely related, and is very similar in appearance, to the Little Egret E. garzetta of the Old World. A few species, however, are found in warmer climates around the world, and most stately may be the Great Egret (left). The large white heron has been the symbol of the National Audubon Society for a hundred years, ever since that organization's early origins in fighting the egret plume trade in Florida (such plumes were once fashionable on women's hats).
The Great Egret has an impressive bill for spearing fish, but it doesn't
hold a candle to the dagger possessed by the Purple Heron (below
left) of the Old World tropics (Africa to se. Asia). These warm-climate
species are often resident, although vagrants do move north into the northern
hemisphere in our summer, bringing vagrants to Europe. But the real world
traveler is the Cattle Egret (below center). It apparently evolved
in the plains of Africa, adapted to following herds of large beasts (elephants
to buffalo to wildebeests), snatching up insects or other prey disturbed
by their passage (and in this photo, it is standing on a pile of hippo
dung!). They then spread before recorded history through tropical Asia
and to Australasia, and were adapted to spinning off vagrants flying far
distances out to sea, reaching the Seychelles in the Indian Ocean long
enough ago to have evolved their own subspecies there. It is 1780 miles
from Africa to South America, but with favorable northeast trade winds
it would take only 40 hours of flying time, and there are three mid-Atlantic
islands to stop at enroute (Hancock & Elliott 1978). The first known
Cattle Egret to reach South America was in 1880; but the time the first
specimen was taken there in 1937, they were nesting. They then invaded
North America via two routes (Central America and across the Caribbean
from Trinidad) during the 1940s & 1950s, and by 1956 were scattered
from Florida to Boston (Davis 1960). The first one reached California in
1962. Today, huge colonies exist at the Salton Sea and smaller colonies
dot the state north to the Oregon border.
The two more secretive subfamilies of herons are the tiger-herons,
such as the Bare-throated Tiger-Heron (above left) of the Central
America lowlands and mangrove swamps, and the bitterns, like the American
Bittern (above right) which breeds from Alaska to Mexico. Each of these
is a treat to find, hidden as they often are among reeds and holding still.
Some tiger-herons and the tiny Zigzag Heron frequent small pools in the
rain forest understory, making them elusive and special. One of the primarily
highlights of a trip to La Selva Lodge on the Napo River in eastern Ecuador
was being taken out before dawn in a small canoe by a local guide, who
paddled close to the thickets growing along the shore of the oxbow lake,
and called out a Zigzag Heron for Rita's birthday in 1992. Yet another
scarce inhabitant of quiet South American waterways is the Agami Heron
(below), hiding here in watery shadows like a Chinese vase painting.
While
there is now general agreement on the subgroups of the heron family, there
is still disagreement about the number of species. A major bone of contention
is how to handle the genus Butorides, such as this Green Heron
(right). I absolutely agree with the approach of Sibley & Monroe (1990)
and Clements (1991) to split this worldwide genus into at least three species,
but Hancock & Elliott (1978) and Martínez-Vilata & Motis
(1992) still lump them all together.
This shot of Green Heron also illustrates one feeding technique of the
herons -- the quiet stance on a limb over the water and then a quick jab
as a small fish swims by. Other herons feed by stirring up the muddy bottom,
jabbing at prey which is disturbed (Snowy & Little egrets), or quiet
standing in the shallows (Great Egret). A very unique technique is used
by the Black Heron of Africa and Madagascar (below), called "canopy
feeding." Following a African Spoonbill Platalea alba, which is
stirring up the mud, the Black Heron spreads its wings to create a shadow
on the water, as if a protective log was above. Small fish often gather
in such shadows, but here they will be running to "shelter" which is their
doom.
So the herons present a great array of biodiversity within a single family
of birds. A gaggle of colorful ones, such as these Pied Herons in
New Guinea (dark-headed adults and a few white-headed youngster), are always
an impressive sight. And finally there are vagrants from time to time,
some reaching my home county in central California, and a photo of one
such bird in 1999 (a Tricolored Heron) is elsewhere
on this web site.
Finally,
I'll conclude this brief summary of the herons with one so strange in appearance
that it was considered a separate family (the Cochleariidae) when I was
growing up. Austin & Singer (1961) described the Boat-billed Heron
(right) as "imperfectly known, for it spends its days hidden in the mangrove
thickets and come out to feed chief at night" when it fed with "its broad,
scooplike bill [that was] totally unlike that of any other bird in the
order." It is, indeed, a primarily nocturnal species of freshwater mangroves
from western Mexico through Brazil, but today it is simply considered an
aberrant night-heron, sharing with them many features and habits and differing
primarily in the outlandish bill. I was fortunate to take this shot at
a day-time roost before it slipped back inside cover.
Photos: The adult Yellow-crowned Night-Heron Nyctanassa violacea was taken from a boat on the Estero San Cristobal, San Blas, Nayarit, Mexico, on 28 Feb 1987. The adult Little Blue Heron Egretta caerulea was in Shark Valley, Everglades Nat'l Park, Florida, U.S.A., in Jan 1999. The Great Egret Ardea alba was being reflected in Moss Landing harbor, Monterey Co., California, on 13 Feb 1996. Both the Purple Heron Ardea purpurea and the Cattle Egret Bubulcus ibis were at Lake Jipe, Kenya, on 26 Nov 1981. The Bare-throated Tiger-Heron Tigrisoma mexicanum was also along Estero San Cristobal, San Blas, Mexico, on 28 Feb 1987. The American Bittern Botaurus lentiginosus was hiding in the reeds at Palo Alto baylands, San Mateo Co., California, on 1 Dec 1986. The Agami Heron Agamia agami was a highlight of a dawn canoe ride on Cocachoca, Tambopata Nature Reserve, Peru, on 24 June 1987. The Green Heron Butorides virescens was in Everglades National Park, Florida, in Jan 1999. The Black Heron Egretta ardesiaca was at Lake Jipe, Kenya, on 26 Nov 1981. The horde of Pied Herons Ardea picata were at the Port Moresby sewer ponds, Papua New Guinea, on 14 Oct 1983. And the Boat-billed Heron Cochlearis cochlearis was in the Pantanal of Mato Grosso, Brazil, in Aug 1999. All photos © D. Roberson.
Bibliographic note:
Family book: Rating HHH
Hancock, James, and Hugh Elliott. 1978. The Herons of the World. Harper
& Row, New York.
This is a large format family book, the type I usually like. It has fine full-page paintings by Robert Gillmor and Peter Hayman of all the species, with good habitat surrounding some of them, and yet even the art often looks flat. The authors know the subject matter, but they seemed constrained by the format: 1 full page artwork and three pages of text. This gives totally inadequate space to well known species like Gray Heron, Great Blue Heron, or Cattle Egret. There is essentially no details on geographic variation, no biometrics, and the maps are stuck way in the back. Vagrants are ignored. And I didn't care for the conservative taxonomy. So, while this could have been great, it ends up fairly mediocre. [I am aware there is a latter edition in a smaller format called "The Heron Handbook," but by the same authors, I think, and I've not looked at it. It wasn't the large format that was the problem... it was the use of that space.]A nice introduction to the family is in Martínez-Vilata & Motis (1992). While I didn't agree with their taxonomy either, this source has the single best collection of heron photos one could ever imagine!
Literature cited:
Austin, O. L., Jr., and A. Singer. 1961. Birds of the World: A Survey of the Twenty-Seven Orders and One Hundred and Fifty-five Families. Golden Press, New York.TOPClements, J. F. 1991. Birds of the World: A Check-List. 4th ed. Ibis Publishing, Vista, CA.
Davis, D. E. 1960. The spread of the Cattle Egret in the United States. Auk 77: 421-424.
Martínez-Vilata, A., and A. Motis. 1992. Family Ardeidae (Herons) in del Hoyo, J., Elliott, A., & Sargatal, J., eds. Handbook of the Birds of the World. Vol. 1. Lynx Edicions, Barcelona.
Payne, R. G., and C. J. Risley. 1976. Systematics and Evolutionary Relationships among the Herons (Ardeidae). Misc. Publ. Mus. Zool. Univ. Michigan 150.
Sibley, C. G., and B. L. Monroe, Jr. 1990. Distribution and Taxonomy of Birds of the World. Yale Univ. Press, New Haven, CT.