THE YEAR OF THE HERON
SPRING / SUMMER / FALL / WINTER

SPRINGHeron Feed image

(March - April - May)

When spring days lengthen, solitary Great Blue Herons on wintering sites scattered from Colorado to the northern rim of South America stir
and seek the company of their kind. Since September,
they have led independent, separate lives.
Spring's subtle changes rekindle a collective urge to gather
in small gender groups called sieges and journey north.
Males depart first.
They feed and rest on the way.
If storms do not slow their progress, the first birds arrive here by mid-March.


With the commotion and contention of a land rush, arriving males compete for prime spots in the rookery. More important than the condition of a remaining nest is its location in the colony. Dominant older birds claim the prized interior sites protected by distance and perimeter nests from predator access. Presence, posture, aggressive snaps and disdainful squawks toward competitors secure a 10' to 15' territory. Young males yield submissively to the older birds. A third year bird may attempt to claim an unoccupied outlying nest or gather a few twigs and start to build a new one.

TYPICAL CALENDAR OF SPRING EVENTS


After a week of positioning and posturing, male herons preen and patiently await the females' return. Perched on their nests in prime nuptial plumage, males greet arriving females by extending their necks skyward, fanning their display feathers and clacking a dissonant "notice me" chorus. At the Fountain Creek rookery, which lies in the municipal airport's landing path, these greeting gestures have been extended amorously to planes passing overhead.

Herons return to the same rookery each year,
but individuals usually bond with a new partner annually.

Gathering females tour the rookery and respond with interest to the locations of nests and each occupant's display. They perch on nearby branches and inch in for closer views. Males initially greet these advances menacingly by extending their necks and rattling the same aggressive squawks directed at real estate rivals. Persistent interest and presence gradually ease these tensions.

Circle flights follow. As attraction grows, the male or female will fly around a prospective partner with its neck outstretched. During normal flight, herons loop their necks back in an "S" position, distinguishing them from other large airborne birds. Some consider the straight-necked flight a display of physical fitness and vigor. Occasionally during these first weeks of courting, the entire colony will circle the rookery and adjacent wetlands in this stylized, extended flight posture. These group displays serve to unify the colony and may synchronize the breeding cycles of separate pairs.

First, second and most third year birds are excluded from these interactions. Third year males pair only if females remain after the older herons have bonded. Shunned breeders soon disperse and lead solitary lives by outlying wetlands for the rest of the summer.

As courtship advances, pairs close their distance. Side by side perching, fanned plume displays, neck twining and paired beak clacking heighten mutual attraction. A female commits to a particular mate when she accepts his ceremonial offering of a twig, signaling the beginning of building a nest and family together. Mutual grooming follows. Partners preen each other's showy display plumes, feathers that appear only this time of year.


Soon the male busies himself with frequent trips
to gather twigs from surrounding trees.

He presents each beakful of building material to her for proper placement in the nest. Younger, less assertive pairs may not find a nest to refurbish. Their efforts account for the new construction at the perimeter of an expanding colony. After several seasons' use, with annual additions of sticks, grass and mud, some of these nests will weigh 20 to 30 pounds and measure 6' across.

Unless winds or late snows prolong renovation efforts,
the female turns her attention to egg laying by mid-April.

Producing one egg a day, she continues for three to five, occasionally seven days. Incubation begins before the final egg appears. After she completes her clutch, pairs alternate incubating the eggs. The parent away from the nest gathers food from neighboring wetlands or roosts and preens itself in a distant tree. On the nest, the resident adult stands every 20 to 30 minutes, stretches its beak down among the eggs and gently rolls each one to warm it evenly. This pattern continues for 28 to 30 days.

By mid-May, the eggs begin to hatch in the order they were laid.

A week may separate the hatchlings in large broods. Heron young enter the world with open eyes and down covered bodies. Though initially helpless and dependent on their parents for food, warmth and protection, the chicks grow rapidly. For their first week, an adult continues to provide shelter and warmth by sitting on the nest. During the brood's second week, pointed beaks and curious gazes appear beneath parental feathers. Their rapid growth and constant begging for food soon force the tending adult to a neighboring branch, leaving the nest's rim for the young to perch and await the other parent's return with food.

Picture of a heron
THE YEAR OF THE HERON
SPRING / SUMMER / FALL / WINTER