Great White Heron

Ardea herodias occidentalis

Great White Heron

Great white heron, photographed at Biscayne National Park, Homestead, Miami-Dade County, in February 2017.

A quick glance at this bird might tell you that you're looking at a great white egret. Take a closer look. Its sheer size, face and feather pattern are clues that you're face to face with something completely different and fairly rare.

It's the great white heron, Ardea herodias occidentalis. The question, taxonomically speaking, is what is the great white heron? Some argue that it is a morph, or form, of the great blue, essentially the same bird in every way except for color. Others say that it is different enough from the great blue to be classified as a subspecies. Historically, the great white was considered a species unto itself. Some still do. It's not a hard argument to make, considering its limited range and connection with certain habitats, versus the wide-ranging great blue.

"White" blue herons aren't unusual; the little blue heron starts off life as a white bird and doesn't take on its predominantly blue coloration until it reaches full maturity at about a year old. They're also much smaller than the great white (or great blue, for that matter) and obviously, their white plummage doesn't last.

Great white herons also have a much smaller range than great blues, which at one time or another, are found throughout most of North America. Great whites are found almost exclusively in extreme South Florida, mainly in the Keys (including the northern-most portion of the Keys, Biscayne Bay and Biscayne National Park). There are records of a small number of nesting pairs in the Bradenton area. Also, there are populations throughout the Caribbean and the Yucatan. Where the ranges of the great white and great blue intersect, a third version appears, Wurdemann's heron, A. herodias wurdemannii.

So how rare is this bird? Rare enough that Florida lists it as a species of special concern. Rare enough that the U.S. Fish and Wildlife Service designated great whites for its "critical recovery" classification to protect them and grow their numbers.

So what are the key tells to separate the great white heron from the great egret? Size, as mentioned, above, is one that's fairly obvious. The other is the bill. The great white heron has a much stouter bill compared with the more delicate egret; the bill also has a blue patch at the base where it meets the face.

Great whites eat mostly fish. They hunt day and night in shallows where there are large expanses of turtle grass. They will stand perfectly still, or stalk ever so slowly until they spot their prey, a mullet or needlefish perhaps, then dart forward with their long necks and grab the meal with their bills.

Like other South Florida wading birds, great white herons were nearly hunted into extinction in the early 1900s; the population fell to as few as 100 nesting pairs, according to a FWS estimate. Conservation measures, including creation of the Key West and Great White Heron national wildlife refuges helped the great white to recover. Great whites continued to increase in numbers into the mid-1990s, when the FWS noticed a decline in their population. A three-year study that began in 2007 found that great whites nesting and foraging in Florida Bay were declining while the refuge population was stable. The study concluded that we humans were damaging critical habitat in the bay and disturbing nesting herons. One of the critical problems: degradation of turtle grass beds where the herons forage. The solution: implementing a series of no-motor, no-entry and buffer zones to reduce disturbances and protect the grass beds.

Great whites are year-round residents of Florida. They breed year-round, with November through February as the peak season. Some will produce several broods in a year. They nest mainly in black and red mangroves and other tropical hardwoods; clutches are usually three or four eggs, which require 30 days of incubation. Offspring fledge at seven or eight weeks, but hang around for a month more.

Biscayne National Park

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Published by Wild South Florida, PO Box 7241, Delray Beach, FL 33482.

Photographs by David Sedore. Photographs are property of the publishers and may not be used without permission.