Great Blue Heron Info

updated 3/25/08

The Great Blue Heron: Ardea Herdias - pronounced ARE-dee-ah-her-ODE-ih-as. 

GBHE - Great Blue Heron - 4 letter code used in banding

Great Blue Herons are approx 48 inches tall.  With a wingspan of to up to 6 feet and weigh between 5 and 8 pounds. The GBHE looks like it weighs more, but its bones are hollow. Males are slightly larger  (5 - 15%) than females. How to tell the male from the female is very difficult but can be done by length and color of their bills. Also, each herons has it own markings on the its face. If you study the area between the lore and the back of the eye you will be able to tell a heron apart from another heron. This area is like a human fingerprint, each one having its very own distinctive pattern. They can fly a cruising speed between 19 and 29 miles per hour.   The GBHE has special neck vertebrae that create an "S" shape.  When the GBHE fly, their necks are in an s-shape.

(This picture was taken 5/12/02 at Vasona, notice the "S" in the neck)

The GBHE feeds mainly on fish, land insects, rodents, voles, amphibians (mostly frogs), reptiles and small birds (Ducklings and Goslings).  Occasionally, they also eat aquatic plants and aquatic beetles.

Predation by Red-tailed Hawks, Ravens, Bald & Golden Eagles, and Raccoons.

Identification Tips:

Adult: A bird with definitive plumage or sexually mature

• White crown and face

• Black plume extending from above and behind eye to beyond back of head.

• Brownish-buff neck with black-bordered white stripe down center of fore neck.

• Blue-gray back, wings and belly

• Black shoulder

• Shaggy neck and back plumes in breeding plumage.

This is an Adult Breeding GBHE 

Notice the White Crown and Black Plume

Immature: This term describes any bird older than a nestling or chick that has not reached sexual maturity or its basic winter or first winter plumage and includes the fledgling, post-fledgling and yearling age classes.

• Black Cap

• Brownish-gay back and upper wings

• Lacks shaggy neck and back plumes

• Lacks black plume extending from behind eye.

Terms to describe birds:

• Nestling: a young bird confined to the nest.

• Juvenile or Immature: This term describes any bird older than a nestling or chick that has not reached sexual maturity or its basic winter or first winter plumage and includes the fledgling, post-fledgling and yearling age classes.

• Fledgling: Applies to a bird from the time it is out of the nest until it becomes independent of its parents.

• Post -Fledgling Period:   The juveniles may sometimes be seen foraging for food alongside adult birds but most often they "hunt" alone. Post-Fledgling Period: For a period of several days, the juvenile herons may return to their nest tree or nearby trees.

• Yearling: Young Herons between 12 and 24 months of age.

• Adult: A bird with definitive plumage or sexually mature. Both sexes look alike in all age classes.  Adult male and female GBHE grown long plumes that play an important role in mate selection.

These birds nest in colonies called heronries where as many as 20-50 large stick nests can be seen. A colony is characterized by large stick nests.  Two or more nests define a colony.   A few birds will nest individually as well.

Males arrive in late winter (January/February) and defends his territory in the tree where he plans to build a new nest or restore an old one. The females arrive a couple of weeks later and are selected by the males. From that site, males put on grand displays and shriek loudly when females approach them.  New mates and nests are chosen each year. Birds aged two years or more mate almost immediately upon arrival, usually at the nest or, when on is not available, on a branch. The building of the nest soon follows.  The male gathers nest-building materials, and the female works them into the nest.  A pair takes less than a week to build a nest solid enough for eggs to be laid and incubated. Construction continues during the entire nesting period. Breeding season lasts from February through August. 

Here a GBHE is bringing nesting material to build its nest. Picture taken at Vasona's Rookery. 

Eggs are laid every 2 to 3 days until 2-5, oblong, light blue, duck-sized eggs have been accumulated. At Vasona the herons have an average of 3 chicks per nest. We have had one nest with one chick while another nest has had as many as five.  Incubation lasts about 28 days. Both parents incubate the eggs.  Males incubate during the day and females during the night. Since incubation begins with the laying of the first egg, and the eggs are laid over a period of several days, the chicks hatch asynchronously (not all at the same time).  The parents immediately begin to feed their young, brooding them (sitting on young to keep them warm) only during the first week to ten days of their young lives. However, for another two-four weeks, an adult remains at the nest almost continually: during the day, the male watches the nest while the female hunts for food; at night the roles are reversed. After the first month the parents spend most of their time outside the colony, returning only to feed the young and stand watch for short periods.

An adult arriving at the heronry usually gives a dull guttural cry. The young cry constantly and grab at each others' bills.  The adult rarely flies straight to them, perching instead on a near by branch. After about five minutes or so , the adult goes to the nest and regurgitates predigested food.  The oldest and largest chicks take the lion's share by grasping the adult's bill and catching the food. In about 6 weeks the young are as large as the adults. By the seventh week, they are hopping to nearby branches and by the eighth week they make short flights.  Most GBHE remain in the nest for 9-10 weeks.

Plumage is a reliable indicator of a GBHEs age class.

• Fledgling: (separated from parents) - downy feathers still poke up from grayish crown.

• Juvenile (less than 12 months) - grayish crown; rusty brown edge to wing coverts; absence of plumes.

• Yearling: (12-24 months) - short plumes present on body; beginning of the adult's white crown stripe; first appearance of the adult's dark shoulder patch; reddish tinge  to body plumage.

• Adult: (more than 2 years old) - striking white crown patch; long plumes on the head, neck, back and breast; slate-blue body plumage

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