The intermediate egret (Ardea intermedia) and great egret (Ardea alba) are two similar-looking species of white herons that belong to the family Ardeidae. While they share some physical traits and behaviors, there are distinct differences between these two egret species.
Size and Appearance
The most noticeable difference between intermediate and great egrets is their size. As the name suggests, intermediate egrets are intermediate in size compared to other heron species. They stand about 32-37 inches tall and have a wingspan of around 51 inches. Great egrets are larger, standing 38-47 inches tall with a wingspan reaching 59 inches across.
In terms of plumage, both species are predominately white with long, thin necks. During the breeding season they develop delicate plumes on their backs, chests, and heads. The intermediate egret’s plumes have a greenish-yellow tint while the great egret’s plumes appear pure white.
The bills of both birds are long, straight and yellowish in color. Great egrets tend to have heavier bills. The intermediate egret’s bill may appear slightly thinner and more needle-like.
Their legs are black or dark gray. The great egret has darker legs that are nearly black while the intermediate egret has grayish-green legs.
Geographic Range
Intermediate and great egrets have overlapping ranges across parts of North America. The intermediate egret’s breeding range centers across the southern United States and down into Central America. They are found near inland wetlands and coastal areas from Baja California to South Carolina.
Great egrets have an even wider distribution, breeding from the Western United States through Central America and the Caribbean. Their breeding range extends up the Atlantic Coast to coastal New England.
During migration and winter months, both species expand their ranges substantially. Intermediate egrets winter primarily along the Gulf Coast south through Central America. Great egrets winter along both coasts down to South America.
Habitat
As wading birds, both intermediate and great egrets rely on wetland habitats. They are most often found in shallow, freshwater and brackish wetlands such as marshes, swamps, ponds, lakeshores and rice fields. Less commonly they may forage in tidal flats, estuaries and mangroves.
During the breeding season, these egrets nest in trees and bushes near water. Colonies are usually found over or near wetlands on secluded islands or protected areas. Great egrets sometimes nest in mixed colonies with other herons while intermediate egrets tend to stay separate.
Diet
Intermediate and great egrets are opportunistic predators that eat mainly fish, amphibians and small animals. Typical prey includes:
- Fish
- Frogs
- Salamanders
- Snakes
- Lizards
- Small rodents
- Insects
- Spiders
- Crayfish
- Shrimp
They capture prey while wading patiently through shallow waters. When prey is spotted, they quickly jab with their bills to spear fish or grab other animals. The great egret sometimes shuffles its feet to stir up aquatic life from hiding spots.
Hunting and Foraging
Intermediate and great egrets employ similar hunting techniques as they wade through wetlands. They walk slowly with careful steps, scanning the water for any signs of movement. Their slim bodies allow them to slip through dense vegetation in search of prey.
When foraging and hunting, egrets tend to stand still or move slowly in place for long periods without stirring up sediment. This allows them to spot potential prey passing by. At other times they may shuffle their feet to chase fish or other animals out from cover.
Once prey is in sight, they swiftly thrust their bills down to grab and swallow it whole. Great egrets sometimes flutter their wings over the water to startle and corral fish into a confined space for easier catching.
Breeding
The breeding behaviors of intermediate and great egrets are very similar.
Courtship begins in late winter or early spring with elaborate mating displays. Males and females engage in stretching, preening, head-pumping, and other rituals. Pairs build platform nests high up in trees using sticks and twigs, often in small colonies with other egrets.
Females lay a clutch of 3-5 eggs which are incubated for around three weeks until hatching. Both parents feed the young birds regurgitated food as they grow over the next few weeks. The young fledge at 6-7 weeks old but may still be fed by parents for some time after.
Intermediate egrets typically have one brood per year while great egrets may nest twice in a season if conditions allow. The nests, eggs, and young are frequently predated by crows, grackles, vultures, racoons, and other opportunistic species.
Migration
Both intermediate and great egrets migrate between breeding and wintering grounds. Their migrations tend to follow coastlines as they travel between habitats.
Intermediate egrets begin leaving breeding grounds along the Gulf Coast as early as July. They start arriving on Caribbean wintering sites by August. Return migration to southern U.S. breeding areas occurs February through April.
Great egrets start migrating northward in February and March. Fall migration back to southern wintering areas occurs September through November. Some great egrets are permanent residents in warmer southern regions like Florida and the Gulf Coast.
Key Differences in Migration Patterns
| Trait | Intermediate Egret | Great Egret |
|---|---|---|
| Winter Range | Gulf Coast, Mexico, Central America & Caribbean | Coasts of U.S., Mexico, Central & South America |
| Migration Timing | July – April | September – March |
| Migration Route | Follows Gulf Coast | Along both Atlantic and Pacific Coasts |
Conservation Status
Both intermediate and great egrets experienced severe population declines in the late 19th century due to hunting pressure for their decorative plumes. Their numbers rebounded in the 20th century after hunting was banned and wetland protection improved.
The great egret is considered a species of Least Concern by the IUCN. Global populations are estimated at around 1 million individuals and are generally stable or increasing in most regions.
Intermediate egrets have a smaller global population around 130,000 individuals. Loss of wetland habitat remains a concern, putting the species at Near Threatened status on the IUCN Red List. Ongoing conservation programs aim to protect key wetland habitats across their range.
Summary of Key Differences
While intermediate and great egrets have some behavioral and habitat similarities, there are key differences between the two species:
- Great egrets are larger in size with a wingspan up to 59 inches, compared to 51 inches for intermediate egrets.
- Intermediate egrets have yellow-greenish plumes, great egrets have pure white plumes during breeding season.
- Intermediate egrets breed primarily in the southern U.S. and Mexico while great egrets breed farther north up the Atlantic Coast.
- Great egrets have a larger winter range extending down the Pacific Coast and south to Chile.
- Intermediate egrets are classified as Near Threatened while great egrets are Least Concern conservationally.
Understanding the unique traits of each species helps birders properly identify and appreciate them in the wild. Protecting the sensitive wetland ecosystems they both rely on will be key for their continued success across the Americas.
Conclusion
The intermediate and great egrets are elegant white wading birds that inhabit wetlands across North, Central and South America. While they may look similar at first glance, important differences in their size, breeding behaviors, geographic ranges and conservation status set them apart. Being able to distinguish these species helps birdwatchers accurately identify them and allows for targeted conservation efforts of their distinct populations and habitats.
