Green herons form mated pairs each breeding season. Courtship displays are elaborate and consist of a specific series of displays. They begin with Flying Around displays resembling natural flight, but oriented to breeding sites with skow calls. This is followed by Pursuit Flight, Circle Flight and Forward displays, where a rasping 'raah-raah' call exposes the red mouth-lining. Next come Crooked-Neck Flight displays, where the neck is partially flexed, legs are dangled, and wingbeats make a noticeable sound. Much like the Crooked-Neck Display, the Flap Flight Display is more intense. Here, the male lurches through the air with exaggerated flapping producing a whoom-whoom-whoom sound in a crooked-neck posture with crest, neck, and shoulder feathers erect and often giving a roo-roo call before landing.
Displays that don't involve flying occur also. In the Snap Display, the male perches, then points body, head, and neck down until his bill tip is at or below the level of his feet and then snaps his mouth together, producing a clicking sound while also erecting his feathers. The Stretch Display involves the male pointing his bill straight up, stretching his neck, and then bending it backwards until the head almost touches its back with the shoulder plumes erect and fanned. In this posture, he sways his neck and head from side to side with crest, breast, and flank feathers sleeked back, eyes bulging, and iris possibly turning from yellow to deep orange while emitting an aaroo-aaroo sound.
Males perform this Stretch Display before a female is allowed to enter the eventual nest area. The female then performs a less intense Stretch silently after the male, which confirms the pair-bond. At this time, the male stops Flight and Snap displays. The pair then nibbles each other's feathers and snap their bills.
Mating System: monogamous
Green herons lay 2 to 4 eggs in a nest at two-day intervals. The eggs are incubated for 19 to 21 days, the young fledge (leave the nest) at 16 to 17 days old and become independent at 30 to 35 days old.
Nests are built in vegetation near water, from ground level up to 20 meters high. The preferred nest spot is a branch in a tree. Nesting pairs normally nest alone, but sometimes nest in small colonies.
Breeding interval: Green herons breed once yearly.
Breeding season: The time of breeding varies considerably geographically, generally breeding begins anytime from March through July.
Average eggs per season: 2-4.
Range time to hatching: 19 to 21 days.
Range time to independence: 30 to 35 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal )
Average eggs per season: 4.
Both parents feed and brood their young, though less often as the nestlings grow.
Parental Investment: altricial ; male parental care ; female parental care
- Davis, W., J. Kushlan. 1994. The Green Heron. The Birds of North America.
- Hancock, J. 1999. Herons and Egrets of the World. London, UK: Academic Press.
- Hancock, J., J. Kushlan. 1984. The Herons Handbook. New York City, NY: Harper and Row Publishers.
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