Grey herons (Ardea cinerea) and great blue herons (Ardea herodias) are two of the most well-known birds in the Ardeidae family, a group containing over 60 species worldwide. Unless you know what to look for, these birds look remarkably similar, so how do birdwatchers tell the difference?
The most obvious difference between grey herons and great blue herons is their size and shape. Great blue herons are taller, heavier, and have longer, s-shaped necks. Another key difference is the rufous thighs and wrists of the great blue heron, which are whitish on grey herons.
When identifying any bird, locality is one of the first places to start. In this case, these birds are rarely confused because they occur on separate continents. The great blue heron is native to North America, while the grey heron can be found in Europe, Asia, and Africa.
Herons and egrets have a way of turning up where they’re not supposed to be, however, and these two species are no exception. Grey herons have been seen in North America, and great blue herons have been seen in Europe, so it's certainly worth knowing the difference.
This article covers the most important (and some less obvious) differences that birdwatchers can look for when identifying these large herons, so keep reading to learn more.
Great Blue Heron
The great blue heron is significantly larger than the grey heron. It is taller, with longer legs, and a longer s-shaped neck. Great blue herons are also substantially heavier than grey herons and have larger bills and larger wingspans.
Blue Heron in flight
In the United States, the grey heron is very rare. They are considered a vagrant species, which means they turn up accidentally from time to time. The great blue heron, however, is a common and widespread species that you could spot at just about any water body from the East Coast to the West.
Grey herons are equally common in Europe, Asia, and Africa where they can be seen in a number of fresh and saltwater environments. Grey heron numbers have increased with modern protection from hunting as well as the construction of dams and the warming climate.
Great blue herons are much larger than grey herons, but size comparisons can be very difficult unless you have the two birds in question standing side by side! Fortunately, there are some other important clues that we can use to distinguish between the two species.
Some of the differences we are going to discuss next are pretty minor, but they all count when trying to make a positive identification. Read on to learn more tips on identifying these similar species.
Grey heron in flight
Distribution is the first clue to consider when identifying these birds, here’s what you need to know:
The grey heron is native to Europe, Africa, and Asia. There have, however, been sightings of this species on islands off North America and in the Caribbean in the following places:
The great blue heron is widely distributed across North America. They can be seen stalking their prey near water bodies across the United States, Mexico, and much of Canada. Interestingly, they can turn up in unexpected places too. Great blue herons have been recorded in Spain and Southern Europe, as well as on the Azores Islands.
Close up portrait of a Great Blue heron
After the difference in size and distribution, plumage color is the best way to tell these two herons apart. Great blue herons have characteristic cinnamon to rufous-brown coloration on their thighs and wrists (carpal region). Grey herons have more white plumage, especially on the underside of the neck, the belly, and the thighs.
Close up of a Grey heron preening its feathers
The most obvious difference between the bills of the two species is their relative size. The bill of the grey heron is much slimmer and lighter than in the great blue heron. If you manage to get a good look, there is a visible difference in the color of the lores of the two species when not breeding.
Lores are the bare patch of skin between the heron’s bill and its eyes. In the grey heron, the lores are dark near the eye, lightening to yellow at the base of the bill. In the great blue heron, the lore is dark from the eye to the bill, except for a small yellow patch in the middle.
Great Blue Heron hunting for fish
The legs of the grey heron are shorter and overall paler, especially when not in breeding condition. The overall color is a dull pinkish or greenish-brown.
The great blue heron usually has dark lower legs (tarsal region) with pinkish upper legs (tibial region). This creates a ‘two-tone’ appearance that is helpful for positively identifying the species.
The grey heron, great blue heron, and the cocoi heron (Ardea cocoi) of South America are considered three closely related members of a superspecies. This means their behavior and calls are generally very similar.
Both grey herons and great blue herons produce similar squawking vocalizations. These birds are certainly not songbirds! There is some variation in the calls of both species but great blue herons tend to have a lower-pitched call.
Grey Heron hunting for fish
The females of both great blue and grey herons are significantly smaller than the males. A large female great blue heron and a small male grey heron could therefore be similar in size.
Apart from the size differences, however, the sexes of each species are similar. Look out for the same differences in plumage color, size, and neck length described in this article when comparing female great blue and grey herons.
Distinguishing between juvenile and immature grey and blue herons is more difficult than for adults. This is because juvenile grey herons can show some of the cinnamon coloration that is more typical of great blue herons. Even so, this color tends to be far less pronounced on grey herons, so rufous or cinnamon plumage is still a good indicator for great blue herons.
Juvenile Great Blue Heron
Juvenile Grey Heron
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