| Home: Special status species: Great blue heron: Natural history |
| SPECIAL STATUS SPECIES: GREAT BLUE HERON (Ardea herodias) NATURAL HISTORY |
| |
| General |
| Taxonomy: |
Order: Ciconiiformes; Family: Ardeidae.
|
| Appearance: |
The Great Blue Heron is the largest heron in North America. Adults weigh 2-2.5 kg (4.4-5.5 lbs) and stand 97-137 cm (38-54 in) high with their necks outstretched. The wings, neck, bill, and legs are very long. The sexes are indistinguishable by plumage, but most males are slightly larger than females. The top of the adult’s head is white except for a black stripe that extends from eyes to slender black plumes at the back of the head. The upperparts are greyish blue, the foreneck and breast is streaked with white, black, and rust. Feathers on the upper legs are rust-brown. Breeding herons have long plumes on their breasts, flanks, and backs. The eyes and bill are yellowish. Skin on the legs is dark brown to greenish yellow. During flight, wing beats are deep and slow the neck is held in an S-shape and the legs are stretched behind. On land and in the water, it walks with long strides and the neck is held out-stretched or in an S-shape. |
|
| Feeding Behavior |
| Overview: |
The Great Blue Heron will eat just about any animal it can swallow. This species may feed alone or in aggregations. Individual distances are maintained in a foraging aggregation through aggressively displays.6 Adults may defend foraging territories. This species hunts both day and night. |
| Prey Items: |
Primarily fish, but also aquatic invertebrates (e.g., crustaceans), insects, amphibians, reptiles, rodents and small birds. |
| Method of
Capture: |
This species has two principal fishing techniques. In the first, the heron stands motionless, its neck extended at an angle of about 45° to the water’s surface and waits for a meal to come within striking distance. In the second technique, the heron slowly wades around in about 15 to 25 cm of water until it drives a fish out from a hiding place. In either case, the prey is captured in the bill with a sudden lunging of the head and neck. Individuals may hunt from floating objects (e.g., drift wood, kelp canopy). |
|
| Reproduction |
| Overview: |
This species usually nests in colonies consisting of 10s to 100s of pairs. However, individual nesting pairs are not uncommon. Males choose the nesting site, often choosing areas with nests from the previous year. Each male then defends his territory from other males and displays for approaching females. Mating occurs almost immediately after a female chooses a mate. The female builds a nest using sticks provided by the male. Typically incubation begins sometime between the laying of the first and second eggs in a clutch. Consequently, nestlings hatch asynchronously and vary in age, size, and competitive ability. This often leads to the loss of smaller nestlings when food becomes scarce. |
| Time to Maturity: |
2 years for both sexes (though fledging success increases with age) |
| Longevity: |
Maximum of 23 years,6 but most adults probably live for about 10 years. |
| Breeding
Season: |
Breeding colonies are active from late January into August in the Monterey Bay area11 |
| Frequency
of Breeding: |
Annual |
| Clutch Size: |
3-4 eggs (range 1-8); usually half survive to fledging13 |
| # of Clutches per Season: |
Usually one (may re-nest if the first clutch is lost early in the season) |
| Parental
Care: |
Both parents incubate the eggs (25-29 days) and feed the young until fledging (~ 60-80 days) 6 |
| Mating
System: |
Seasonally monogamous; new mates may be chosen each year |
|
|
| [ Top of page ] |
| |
