Sunday, Dec 21, 2014

Great Egrets, Great White Egrets, White Heron or Common Egret

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Great Egrets


Great EgretsGlobal Names

Distribution / Range

Recognized Sub-species and Ranges

Description and Similar Species

Nesting / Breeding

Diet / Feeding

Calls / Vocalizations

Lifespan / Mortality




The Great Egret (Casmerodius albus / Ardea alba) is a large egret with a global distribution. It is also known as the Great White Egret, the American Egret, the Large Egret or Common Egret. Previously, it was also referred to as the Great White Heron, leading to confusion with the white morph (form) of the larger, closely related Great Blue Heron.

In the early 20th century, they were almost hunted into extinction for their long, attractive feathers that were commonly used as decoration for ladies hats, but their numbers have increased over most of its range and they continue to expand their territories. However, this species is threatened by the degradation of its wetland habitats and, in some areas, by hunting and collecting of their eggs.


Alternate (Global) Names:

Chinese: 大白鹭 ... Czech: volavka bílá ... German: Silberreiher ... Danish: Sølvhejre ... Dutch: Grote Zilverreiger ... Finnish: jalohaikara ... French: Grande Aigrette ... Icelandic: Mjallhegri ... Italian: Airone bianco maggiore ... Japanese: daisagi / ダイサギ ... Norwegian: Egretthegre ... Polish: czapla biała ... Portuguese: Garça-branca-grande ... Slovak: beluša velká ... Spanish: Garceta Grande ... Swedish: Ägretthäger

Great White Egret


Great egret in flight Distribution / Range

Great Egrets mostly occur in tropical areas and temperate regions. They are found in the Americas, Europe, Africa, Asia and Australia. In Australia, they are common in areas with suitable wetland habitat.

In the Americas, they occur naturally from southern Canada through Oregon, Wisconsin, New England and Massachusetts south to Florida and along the Gulf coast, through to western Mexico and Central America, south to Argentina in South America.

Great Egrets are found in both inland wetlands as well as long the coast. They typically inhabit coastal swamps, lake shores, marshy ponds, salt pans, bays, tidal flats, mangroves, floodplains, river margins, mudflats, shallow lagoons, freshwater and saltwater marshes, and estuaries. They also stray into more terrestrial habitats, including damp grasslands, open fields, agricultural land and drainage / irrigation ditches.

They are partially migratory, with those breeding in the northern hemisphere migrating south to winter in warmer areas.

Outside the breeding season, Great Egrets can be seen alone or in small mixed-species flocks. When breeding, they nest in large colonies. At night, they roost in groups.

Great Egrets are native to:

Native: Afghanistan; Albania; Algeria; Angola; Anguilla; Antigua and Barbuda; Argentina; Armenia; Aruba; Australia; Austria; Azerbaijan; Bahamas; Bahrain; Bangladesh; Barbados; Belarus; Belgium; Belize; Benin; Bermuda; Bhutan; Bolivia; Bosnia and Herzegovina; Botswana; Brazil; Brunei Darussalam; Bulgaria; Burkina Faso; Burundi; Cambodia; Cameroon; Canada; Cayman Islands; Central African Republic; Chad; Chile; China; Christmas Island; Colombia; Comoros; Congo; Congo, The Democratic Republic of the; Costa Rica; Côte d'Ivoire; Croatia; Cuba; Cyprus; Czech Republic; Denmark; Dominica; Dominican Republic; Ecuador; Egypt; El Salvador; Eritrea; Ethiopia; Falkland Islands (Malvinas); France; French Guiana; Gabon; Gambia; Georgia; Germany; Ghana; Greece; Grenada; Guadeloupe; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; Hong Kong; Hungary; India; Indonesia; Iran, Islamic Republic of; Iraq; Israel; Italy; Jamaica; Japan; Jordan; Kazakhstan; Kenya; Korea, Democratic People's Republic of; Korea, Republic of; Kuwait; Kyrgyzstan; Lao People's Democratic Republic; Latvia; Lebanon; Lesotho; Liberia; Libyan Arab Jamahiriya; Macedonia, the former Yugoslav Republic of; Madagascar; Malawi; Malaysia; Maldives; Mali; Martinique; Mauritania; Mayotte; Mexico; Micronesia, Federated States of; Moldova; Mongolia; Montenegro; Montserrat; Morocco; Mozambique; Myanmar; Namibia; Nepal; Netherlands; Netherlands Antilles; New Zealand; Nicaragua; Niger; Nigeria; Northern Mariana Islands; Oman; Pakistan; Palau; Panama; Papua New Guinea; Paraguay; Peru; Philippines; Poland; Portugal; Puerto Rico; Qatar; Romania; Russian Federation; Rwanda; Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Saudi Arabia; Senegal; Serbia; Sierra Leone; Singapore; Slovakia; Slovenia; Solomon Islands; Somalia; South Africa; South Georgia and the South Sandwich Islands; Spain; Sri Lanka; Sudan; Suriname; Swaziland; Switzerland; Syrian Arab Republic; Taiwan, Province of China; Tajikistan; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Trinidad and Tobago; Tunisia; Turkey; Turkmenistan; Turks and Caicos Islands; Uganda; Ukraine; United Arab Emirates; United States; Uruguay; Uzbekistan; Venezuela; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Yemen; Zambia; Zimbabwe

They are vagrants to:

British Indian Ocean Territory; Djibouti; Equatorial Guinea; Fiji; Finland; Great Britain; Ireland; Liechtenstein; Luxembourg; Malta; New Caledonia; Norway; Saint Helena; Saint Pierre and Miquelon; Sao Tomé and Principe; Seychelles; Sweden.


Great EgretRecognized Subspecies and Ranges

  • Ardea alba alba (Linnaeus, 1758) - Nominate Race
    • Range: Breed in Central Europe to Central Asia, South to Iran. Winter in North and Central Africa, the Persian Gulf to South China and South Korea
    • The nominate race differs from the American race in having a dark bill during the breeding season instead of a yellow bill with a dark tip. When not breeding, the bill is all yellow.

  • Ardea alba egretta (Gmelin, 1789)
    • Range: North, Central, and South America, from northern USA to Central Argentina.
    • The largest subspecies

  • Ardea alba melanorhynchos (Wagler, 1827)
    • Range: Africa south of the Sahara and on Madagascar

The Eastern Great Egret (Ardea modesta - J. E. Gray 1831) was previously considered a subspecies, but has been given full species status.

Great Egret and Great Blue Heron Composite

Description

Great Egrets measure 28 - 41 inches (70 - 105 cm) in length - from top of the head to the tip of its short tail; with the average length being 31 inches (80 cm). The wingspan is 51 - 55 inches (130 - 140 cm). They average 2.1 lbs (950 grams) in weight.

The plumage is entirely white. During the breeding season, both males and females grow long lacy, delicate and flowing plumes ("aigrettes") on the back that curl over the tail. These display plumes molt out after fall.

Outside the breeding season, the long legs are grey to sooty black. When breeding, the legs turn pinkish-yellow at the top. They have non-webbed feet with long toes.

The bill is straight, long and sharp. In the non-breeding plumage, the bill and surrounding facial skin are yellow. When breeding, the bill turns blackish and the facial skin becomes green.

The neck has a characteristic kinked S-curve.

Gender id:

Males and females look alike; except the males are usually a little larger.

Immatures:

Juveniles look like non-breeding adults, except their yellow bill has a blackish tip.

Similar species

  • The non-breeding Great Egret can be distinguished from other white egrets by its larger size, yellow bill and dark / blackish legs. However, the bill turns darker and the feet lighter when breeding at which time identification is more challenging.

  • The Great Egrets is easily confused with the white morph of the Great Blue Heron - also commonly referred to as the "Great White Heron" - which occurs only in southern Florida. The Great Blue Heron can be identified by its pale yellow legs and feet - compared to the blackish legs of the Great Egret. Also, the Great Blue Heron has a heavier bill.

  • The juvenile white morph (form) of the Little Blue Heron has a dark bill with a bluish base and greenish legs.

  • The Cattle Egret is much shorter and often has a reddish wash over the head, back and breast. It has a yellow bill and blackish legs.

  • The Great Egret is larger than the Snowy Egret. Also the Snowy Egret has yellow feet and a black bill.

  • The white morph (form) of the Reddish Egret has a dark or bi-colored bill.

Flight:

The Great Egret's flight speed has been measured to be 17 - 32 mph (28-51 km/h). Their flight is slow, yet strong. In flight, the neck is pulled back in an S-curve. This distinguishes them from cranes, storks, ibises and spoonbills, which extend their necks in flight.


Calls / Vocalizations

The Great Egrets are generally silent; except breeding colonies, loud croaking cuk cuk cuk can be heard.

Great Egret


Great Egret Diet / Feeding

Great Egrets mostly feed in the early mornings and evening. They forage either alone or in groups.

The largest part of their diet consists of fish, frogs and crayfish. To a lesser extent, they take small reptiles, snakes, snails, small mammals, insects (such as leafhoppers, grasshoppers and aquatic insects) and small birds,

They usually hunt in shallow waters, either moving around slowly with the neck extended searching for prey or standing motionless until the prey comes within striking distance at which time they will spear the prey with the long, sharp bill.

They also follow large mammals (such as buffaloes) on land to feed on the insects they stirred up as they move about. They may also stalk small mammals, such as mice, moles and voles.

The prey is either speared or seized with their bill, and swallowed whole.


Breeding / Nesting

The breeding seasons of the Great Egrets vary with the location:

    • in the southern range, they usually breed between October and March;
    • in their northern range, they mostly breed between March to May;
    • in Florida, USA, most breeding occurs from mid-December through January;
    • in the tropics, they breed throughout the year.

Breeding Plumage:

Great Egrets are of breeding age when they about two years old. As they get into breeding condition, some physical changes can be noted. The lores (featherless skin between the bill and eyes) turn from yellow to lime green, and the top of the upper bill turns dark. After eggs have been laid, the color of the lores changes back to yellow, but the dark markings on the bill remain throughout most of the breeding season (Pratt, 1993).

Arrival at the nesting site ...

They usually nest in trees close to large bodies of water or other extensive wetlands.

Males usually arrive in the breeding territory before the females. It is their responsibility to choose the nesting site and to get started on the nest construction, before even selecting a female. They may reuse the nest of a previous season.

Great Egrets often breed in large, mixed-species colonies that may include other egret species, herons, ibises, herons and cormorants. Colony nesting offers the advantage of added security as the increased surveillance capacities facilitates detecting predators.

Older males will often place their bulky stick nest in the center of the colony. Males or pairs may switch nests or even change colonies. Once they have settled on a location and the nest is completed, they will usually start displaying for the females.

As part of the "courtship dance", the male performs movements that are described as "Stretch," "Wing Preen," "Snap," and "Twig Shake" displays. Interested females gather on branches around the male to watch the display. Some females will perform a ritualized "Circle Flight;" and they may chase other females away. Great Egrets are seasonally monogamous and may reunite with mates of previous years.

Great Egret on nest (note the eggs)

Nesting / Chick Rearing

Once the pair bond has been established, Great Egrets will concentrate on completing the generally flimsy platform nest made out of sticks, twigs and other vegetation. Often the male will take nesting material to the nest, which the female will then arrange to her liking.

The nest is usually situated in a fork of a tree or in a bush or to a lesser extend placed on dry ground near a marsh. The "cup indentation" in the middle may be lined with softer material or remain unlined.

The average clutch consists of 3 to 5 pale blue-green eggs (usually 3, occasionally 2 or rarely as many as 6 eggs). Each egg measures about 2.2 inches (57 mm) in diameter. The eggs are laid at 2 - 3 day intervals. Both parents share the incubation duties, which usually begin after the first or second egg has been laid. The eggs are incubated for about 23 - 28 days.

The chicks usually hatch days apart and there are significant size differences between the oldest and youngest chicks. The hatchlings are semi-altricial, in reference to the fact that hatchlings are capable of limited movement, are covered with down, are not blind, and initially require parental feedings. Both parents feed the chicks regurgitated food. Competition for food between the older and younger chicks is fierce, with the older (larger) chicks typically monopolizing the food while the smaller ones starve when not enough food is delivered to the nest. The parents usually remain close to the nest when foraging for food - however, if necessary, may travel distances of 4 - 12 miles (6 - 20 km) to find food.

The chicks fledge (take their first flight) when they are 42 - 49 days old. If the nest is on the ground, they will usually walk around the nest for a few days before taking their first flight. They are capable of extended flights when they are about 7 weeks old, but are still cared for by their parents until they are about 10 - 11 weeks old.

The parents aggressively defend the nest and their young. Great Egrets typically only produce one brood each season, but may replace a lost clutch or brood.

White Heron


Lifespan / Mortality:

Great Egrets have a very high mortality rate of 76% in the first year (particularly during the nesting and fledging period). Those that survive can live 10 to 20 years or more - although the average lifespan is about 5 years. The oldest recorded Great Egret lived to 22 and 10 months.


Great Egret Photo Gallery


Great Egret chicks with full crops

Great White Egrets

Great Egrets

Great Egret with chicks

Species Research by Sibylle Johnson

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