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Green Heron (Butorides virescens)

Green Heron

Butorides virescens

(Order Ciconiiformes; Family Ardeidae)

Butorides virescens perching  http://www.ridgewoodcameraclub.org/omalley_p.html

Diagnosis: Green Herons have a very short and stocky body build. Their bill is sharp, pointy, and dark in coloration. Similar to most heron species, they have a very long neck, but usually do not keep it elongated, instead holding it tight with the body. Whereas most other herons have long legs, the Green Heron has very short yellow legs. The adults adorn a shiny greenish black colored head with black crest, and a rust colored neck. The wings are a grey-black that turn to either a blue or green color, and their underside is grey. Males are slightly larger than females, and are also more brightly colored, more so during the breeding season. Coloration of the juvenile is different and quite dull from that of an adult; the sides of the head, neck, and underbelly are streaked with white and brown, and they have greenish-yellow colored legs and bill. Hatchlings are covered in light grey-white down. On average the adult birds are about 45 cm in length, and weigh around 175 g, which is about the size of a large crow.

Natural History:

Although a very common bird, they are rarely observed because of their shy nature. Besides during breeding season, they are a solitary animal. They are active both during the day and night, and can be found hunting throughout the entire day.

The Green Heron has many characteristic behaviors, including many courtship displays and hunting techniques. Pursuit Flight, Circle Flight and Forward and Stretch displays are a few courtship displays of this bird. One of the more aggressive courtship displays are the Crooked-Neck Flight, which is a stance in which the neck is flexed, and the feet are dangling while the bird is aerial. The wings are exaggeratedly flapped and are very audible, making themselves very apparent to their female counterparts. Another characteristic behavioral display that may help with identification is the tendency for the bird to defecate a white stream behind itself when flying away from a disturbance.

The Green Heron is a somewhat migratory species (dependent upon individual populations), and migration is dependent upon breeding season variables. Factors such as food availability and rainfall effect the onset of the breeding season, which differs geographically, but usually begins from March through January.  For those populations that are non-migratory, after the breeding season is over they roam about the region. If they find a more suitable habitat, they will relocate to that area, and if not, they will return to their previous location. This is also the time period during which those who choose to migrate do so. Winter migration begins in September, and the Green Heron is absent from the regions they do not inhabit year round by the month of October.

Green Herons only breed one time each year, and they are seasonally monogamous. They are very territorial and aggressive, especially when it comes to their nesting sites, and will defend their territory both before and after mating. The male chooses a nesting site before selecting a mate, and then performs one of its many courtship rituals in pursuit of attracting a suitable partner. In order to confirm pair bonding, both the male and the female perform the Stretch Display, which is done before the female is allowed into the nest. The male points his bill straight up and stretches his neck, and then bends it backwards until it touches his back. Its feathers are also fanned around the body, and once set in this position, the eyes will begin to bulge and possibly change to a deep orange color, and he will begin to sway his head and neck from side to side. The females perform the same display but on a less intense note. Once paired up, both sexes make the nest together, and this is when copulation takes place.

The average clutch size is between 2 and 6 eggs, which are not laid consecutively, but in intervals of usually two days. Incubation begins after the first egg is laid and continues for about three weeks, and is done by both the mother and the father. The young begin to branch around two weeks old, but are dependent on their parents until around 30-35 days of age. Both males and females are sexually reproductive at one year of age.

Some known predators include other larger birds, snakes, and raccoons. The average life span is 8 years.

Distribution:

The Green Heron is prevalent in a majority of the eastern United States from Canada to the Gulf of Mexico, and as far west as California during the winter months.

Green Heron Range Map http://sdakotabirds.com/species/maps/green_heron_map.htm

Habitat: The Green Heron live in forest or swamp areas close to fresh water. They build nests out of sticks and shrubs, mostly in low lying trees. During the winter months when they migrate to the coast, they often prefer mangrove swamps.

Diet: Fish is the primary food source of the Green Heron, although they may eat other crustaceans, small rodents, and insects, and generally feed at the edge of a water source.

They are known to use 15 different techniques for catching food and have been acclaimed to be one of the smartest bird species. Baiting with insects or other attractive fish foods is the most interesting to watch.

Video:

Conservation Status: Least concern

Links:

Wikipedia. Green Heron: http://en.wikipedia.org/wiki/Green_Heron

Bird Web. Seattle Audubon Society: http://www.birdweb.org/birdweb/bird/green_heron

10,000 Birds. Green Herons and their Groovy Necks: http://10000birds.com/green-herons-and-their-groovy-necks.htm

References:

Butzbaugh, J. 2001. Butorides virescens. Animal Diversity Web.

Florida Fish and Wildlife Conservation Commission. 2003. Florida's Breeding Bird Atlas: A Collaborative Study of Florida's Birdlife.

Talcroft, C. 2009. Sonoma County Bird Watching Spots.

Image Credits:

Ridgewood Camera Club. http://www.ridgewoodcameraclub.org/omalley_p.html

Green Heron Range Map. Created by Terry Sohl. http://sdakotabirds.com/species/maps/green_heron_map.htm

Submitted By:  Shanay R. Cantu-Chambers, July 2012

 

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