The Great Blue Heron (Ardea herodias) is a prominent wading bird found across North, Central, and parts of South America. It is the continent’s largest heron, recognized by its blue-gray plumage, long legs, S-shaped neck, and sharp bill. Great Blue Herons are commonly observed in diverse aquatic environments, including marshes, wetlands, lakes, and rivers, adapting to habitats from subtropical swamps to northern Canadian provinces.
Arboreal Nesting Preferences
Great Blue Herons predominantly construct nests in trees, offering several advantages for successful breeding. This elevated placement provides significant defense against ground predators, making nests less accessible. While height offers a broad overview, their primary foraging occurs in shallow waters, not directly from the nest.
Herons select tall, sturdy trees for nesting, often choosing dead or dying trees, or those on islands or isolated spots near water. They prefer deciduous trees, though conifers are also used. Proximity to foraging grounds like lakes, rivers, and wetlands is crucial for a readily available food supply. Nests can be high in the canopy, sometimes over 100 feet above ground or water.
Life Within the Rookery
Great Blue Herons are colonial nesters, forming large breeding aggregations known as “rookeries” or “heronries.” Colonies vary in size, from a few nests to several hundred, typically averaging around 160. Though primarily single-species, herons sometimes nest alongside other wading birds, benefiting from shared defense and foraging information exchange.
Nest construction is a cooperative effort; the male gathers sticks and twigs, while the female weaves them into a substantial platform. These bulky nests, initially about 20 inches across, can grow to over 4 feet wide and 3.5 feet deep with repeated use. The nest cup is lined with softer materials like pine needles, moss, leaves, or dry grass, providing a secure space for eggs.
The breeding season begins in early spring, with eggs laid from March to April in northern regions. Females lay two to seven pale blue eggs, with three to five being common. Both parents share incubation duties for 27 to 29 days. Chicks hatch asynchronously and are fed by both parents through regurgitation. Young herons remain in the nest for 49 to 81 days, developing rapidly before their first flight and dispersal.