Bird of the Month: Great Blue Heron
By Hugh Jennings
PC: Mick Thompson (Great Blue Heron)
Scientific Name: Ardea Herodias
Length 46 in
Wingspan 72 in
AOU Band code GBHE
The Great Blue Heron (GBHE) is about 46" long and has a wingspan of 72". The Puget Sound region has a specific sub-species, Ardea herodias fannini. It is our largest and most common heron, about the size of a Sandhill Crane.
It has grayish-blue body, white head with a black stripe over the eye. The Puget Sound sub-species has a slightly darker color and are non-migratory. Breeding adults have a straight, dagger-like yellow bill and ornate plumes on its head, neck, and back. Non-breeding adults lack plumes and the bill is yellower. Immature GBHEs have a solid black cap that gradually changes to white over two years. Their calls are a harsh guttural "frahnk" or a short "rok-rok" given during aggression.
They are found in almost all water areas--marshes, wetlands, rivers, tidal flats, mangroves. They stand or wade in shallow water and grab prey with their serrated bill. The GBHE primarily feeds on fish. In the spring they will feed on frogs and marine invertebrates. In the winter it will feed on land on small mammals.
The GBHE nests in colonies, or heronries, of 7-250 pairs, usually 7-60 pairs in our area. Small colonies are more subject to predation. Some birds at the tops of trees act as sentinels to warn of danger. Crows, hawks and eagles feed on the eggs while hawks and eagles feed on the young. It is estimated there are 2400 nesting pairs in the 1990s in the Puget Sound region.
The nest is a large platform of sticks lined with twigs or vegetation and is built in the highest parts of tall trees, commonly alders and cottonwoods. Old nests are reused. They are continually rebuilt and repaired during the nesting season. Four pale bluish green eggs are laid. These hatch in about 28 days. By the time the young fledge 55-60 days later there will usually be only two young left.
GBHEs are found all year in the west and south. Its breeding range extends to northern US and southern Canada. By April 1 they have probably finished laying eggs. It is even possible for some early nesters to have hatched young. There are a number of heronries in the Puget Sound area, including Kenmore P&R, Lake Sammamish State Park, Bellefields Nature Park, Peasley Canyon in Kent, and Black River heron colony in Renton.
For more information, see the April 1984 National Geographic magazine which has a lengthy article about Great Blue Herons. The pre-eminent authority on the Puget Sound sub-species is Robert W.Butler who has written a book entitled "The Great Blue Heron".